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#5807

The Catholic Church is infallible

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The participant that receives the most points from the voters is declared a winner.

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Description

The ultimate goal of this debate is to advance the pursuit of truth. Regardless of who wins or loses, the real victor is the one who gains new knowledge. This debate will examine the basis for the Catholic Church's claim to infallibility.

Opponents of the dogma are the Reformers, who in rejecting the hierarchy also rejected the authoritative teaching-function of the Church; and the Modernists, who deny the Divine institution of the Church and therefore also set aside her infallibility.

Definitions:

Infallible - The impossibility of falling into error. In this context, the term refers to the Church's infallibility in the final decision on doctrines concerning faith and morals.

Rules:

1. Both parties accept the Bible as divinely inspired and authoritative.
2. For consistency, the NRSV Bible will be used as the reference when citing scripture.
3. In the final round, only counterarguments addressing previous points will be allowed; no new arguments may be introduced.
4. Failure to comply with rule #3 will result in an automatic forfeiture.

Round 1
Pro
#1
INTRODUCTION.

Welcome, and thank you all for taking the time to engage with this debate. This debate focuses on the Catholic Church's claim to doctrinal infallibility — a concept rooted in the Church’s understanding of divine guidance and Christ’s promises. I will argue in support of this belief, presenting its historical and theological foundations, while my opponent critiques its validity. Together, we will examine scriptural and historical evidence to uncover the strengths and weaknesses of each position. With a comprehensive approach to scripture and theology, I am genuinely excited about the enlightening arguments and insights this exchange will bring.

I would also like to express my heartfelt gratitude to my opponent for their willingness to engage in this debate. Their time, effort, and intellectual curiosity are deeply appreciated. However, regardless of the debate's outcome, the real victory lies in the knowledge and understanding that all participants and readers gain from this discussion.

PREREQUISITE.

As both sides agree on the Bible's authenticity and divine inspiration (as stipulated in the rules), I will appeal to it as a reliable and authoritative source. My argument will focus on how Scripture supports the Catholic Church's claim to infallibility, emphasizing Christ's promises to His Apostles and their successors.

The Church’s authority rests on the foundation of an unbroken chain of apostolic succession, beginning with the twelve Apostles chosen by Christ. Entrusted by Christ with the mission to teach, govern, and sanctify, these Apostles passed on their authority to successors, the bishops, through the laying on of hands and the sacrament of Holy Orders (Acts 1:15-26; CCC 77, 861). This succession ensured the Church’s continuity in teaching authority from the Apostolic Age to the present day, fulfilling Christ’s promise to remain with His Church “to the end of the age” (Matthew 28:19-20). Scripture further reinforces this in 2 Timothy 2:2, where Paul instructs Timothy to entrust his teachings to reliable men who can continue the mission.

Historical evidence for apostolic succession is affirmed by early Church Fathers like St. Clement of Rome (circa AD 95), who emphasized orderly succession as crucial to maintaining Church unity and doctrine (1 Clem. 42-44), and St. Irenaeus of Lyons (circa AD 180), who declared that the apostolic tradition is preserved through a continuous lineage of bishops, tracing back to the Apostles themselves (Adv. haer. III 3:1). This principle was formally institutionalized at the First Council of Nicaea (AD 325), which addressed theological disputes and confirmed the bishops’ role as guardians of the apostolic faith. The Nicene Creed describes the Church as "one, holy, catholic, and apostolic," affirming the continuity of its foundation in the Apostles (CCC 861 ;  D 86). The scriptural, historical, and theological basis for apostolic succession demonstrates that the Church’s authority is not an innovation but a divinely established reality, preserved through centuries of consistent practice and belief.

MAIN BODY.

Christ promised his Apostles the assistance of the Holy Spirit for the fulfilment of their teaching task. In His discourses to the Apostles at the Last Supper, several passages occur which clearly imply the promise of infallibility. John 14:16-17: "I will ask the Father, and he will give you another Advocate, to be with you forever. This is the Spirit of truth, ... he abides with you, and he will be in you." "But the Advocate, the Holy Spirit, whom the Father will send in my name, will teach you everything, and remind you of all that I have said to you." (John 14:26). "When the Spirit of truth comes, he will guide you into all the truth; for he will not speak on his own, but will speak whatever he hears, and he will declare to you the things that are to come." (John 16:13). The same promise is renewed immediately before the Ascension in Acts 1:8. What does the promise of the Holy Spirit's perpetual and effective presence and assistance — the Spirit of truth — mean in relation to doctrinal authority, except that the Third Person of the Blessed Trinity is made responsible for what the Apostles and their successors may define to be part of Christ's teaching? Insofar as the Holy Spirit is responsible for Church teaching, that teaching is necessarily infallible: what the Spirit of truth guarantees cannot be false.

"All authority in heaven and on earth has been given to me. Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, and teaching them to obey everything that I have commanded you. And remember, I am with you always, to the end of the age." (Matthew 28:18-20 ; Cf. John 14:16 ; 16:13. Acts 1:8). Anyone who acknowledges that Christ established a visible Church with teaching authority must admit that this commission was entrusted not only to the Apostles during their lifetimes, but also to their successors until the end of time, "I am with you always, to the end of the age." The perpetual assistance of Christ and of the Holy Spirit guarantees the purity and the integrity of the promulgation of the faith of the Apostles and of their successors. Christ demands unconditional "obedience of faith" (Romans 1:5), promulgated by His Apostles and of their successors, and makes eternal salvation dependent on this: "The one who believes and is baptized will be saved; but the one who does not believe will be condemned." (Mark 16:16). He positively identifies Himself with them: "Whoever listens to you listens to me, and whoever rejects you rejects me." (Luke 10:16 ; Cf Matthew 10:24 ; John 13:20). This presupposes that the Apostles and their successors, in their promulgation of faith, are removed from the danger of error. The infallibility of the promulgation of faith is a presupposition of the unity and of the indestructibility of the Church.

St. Paul sees in the Church "the household of God, which is the church of the living God, the pillar and bulwark of the truth." (1 Timothy 3:15). Such a description would be more than mere exaggeration — it would be outright misleading — if applied to a fallible Church. However, St. Paul clearly intended it as a sober and literal truth, as evidenced by his strong emphasis elsewhere on the Divine authority of the Gospel. This Gospel, preached by him and the other Apostles, was entrusted to their successors to proclaim faithfully and without corruption until the end of time. To the Thessalonians, he writes, "when you received the word of God that you heard from us, you accepted it not as a human word but as what it really is, God’s word." (1 Thessalonians 2:13). To the Corinthians, he affirms that the Gospel is meant to "take every thought captive to obey Christ." (2 Corinthians 10:5). The unchanging and authoritative nature of Apostolic teaching is evident in St. Paul's warning to the Galatians (1:8) to anathematize (curse or condemn) anyone — even an angel from heaven — who preaches a Gospel different from the one he had delivered. This stance, which assumes the infallibility of the Apostolic College, was not unique to St. Paul. Other Apostles and apostolic writers similarly condemned those who proclaimed a distorted version of Christianity (cf. 2 Peter 2:1 seq.; 1 John 4:1 seq. ; 2 John 7 seq.; Jude 4). Furthermore, St. Paul emphasizes that his authority did not stem from personal or private views but from the Gospel entrusted by Christ to the Apostolic body.

SUPPORTING BODY.

In the battle against false teaching, the Fathers emphasized that the Church always preserved unfalsified the truth handed down by the Apostles, and will preserve it for all time. St. Irenaeus stresses as against the Gnostic error, that the promulgation of the Church is always the same, because she possesses the Spirit of the Holy Spirit, the Spirit of Truth: "Where the Church is, there is also the Spirit of God, and where the Spirit of God is, there is the Church and all grace ; but the Spirit is truth" (Adv. haer. III 24:1). St. Irenaeus argued that the Church is the house of the truth, from which false teaching is excluded (Adv. haer. II - III). The unfalsified tradition of the apostolic teaching is guaranteed by the uninterrupted succession of the Bishops from the Apostles downwards. "They (the Bishops) have received the certain charisma of the truth according to the pleasure of the Father, with the succession in the office of Bishop." (IV 26:2). Cf. Tertullian, De praesc 28 ; St. Cyprian, Ep 59:7. The intrinsic basis of the infallibility of the Church lies in the assistance of the Holy Spirit, which was promised to her especially for the exercise of the teaching office. Cf. S. th. 2 II 1:9.

The Church, in her corporate capacity, after the example of the Apostles at Jerusalem, always acted on the assumption that she was infallible in doctrinal matters, and all the great orthodox teachers believed that she was so. Those who presumed, on whatever grounds, to contradict the Church's teaching were treated as representatives of Antichrist (Cf. 1 John 2:18 seq.), and were excommunicated. It is clear from the letters of St. Ignatius of Antioch how intolerant he was of error, and how firmly convinced that the episcopal body was the Divinely ordained and Divined guided organ of truth; nor can any student of early Christian literature deny that, where Divine guidance is claimed in doctrinal matters, infallibility is implied.

So intolerant of error was St. Polycarp, that when he met Marcion on the street in Rome, he did not hesitate to denounce the heretic to his face as "the first-born of Satan" (Polycarp, Ep. Phil. 7). This incident is thoroughly in keeping with "the Spirit of the Age, who will be with the Apostles until the end of time" (Cf; Matthew 28:19-20). Such a spirit is incompatible with belief in a fallible Church. Tertullian, writing from the Catholic standpoint, ridicules the suggestion that the universal teaching of the Church can be wrong: "Suppose now that all [the Churches] have erred . . . [This would mean that] the Holy Spirit has not watched over any of them so as to guide it into the truth, although He was sent by Christ, and asked from the Father for this very purpose — that He might be the teacher of truth" (Tertullian, De praesc 28).

OBJECT OF INFALLIBILITY.

The Church possesses the authority to determine and propose the meaning of the teaching of Revelation. This authority extends not only to authentic declarations of Holy Scripture, the testimonies of Tradition, or the formulation of creeds and doctrines, but also to identifying and rejecting errors that contradict divine revelation. Without this infallible authority, the Church could not fulfill her role as the "guardian and teacher of the revealed word of God" (D 1793 ; D 1798). This authority ensures that her teachings on faith and morals remain free from error and faithfully reflect the truth entrusted to her by Christ.

This doctrine is a necessary extension of the teaching on infallibility, which exists to “preserve and truly interpret the deposit of Holy Faith” (D 1836). Critics often argue that infallibility implies overreach or the suppression of dissent, but the Church's infallibility is strictly limited to final, authoritative decisions on matters directly connected to faith and morals. This scope reflects the Church’s fidelity to Christ’s promise that the Spirit of Truth would guide her into all truth (John 16:13). Moreover, if the Church were capable of error in her final judgments, it would undermine the very mission given to her by Christ. Such errors would compromise the unity of faith, contradicting the Church's identification as "the pillar and bulwark of the truth" (1 Timothy 3:15). Historical controversies or instances of individual failings do not pertain to the Church's infallibility in doctrinal definitions, which is strictly limited to definitive teachings on faith and morals. Rather, they highlight the distinction between fallible human actions and the divine guidance promised to the Church in her teaching office. 

Thus, the Church’s ability to infallibly decide on doctrine is not only a practical necessity for safeguarding the truth but also a reflection of her divine mandate. Without this charism, she could not protect her faithful from doctrinal error or fulfill Christ’s command to teach all nations with authority (Matthew 28:18-20).

CONCLUSION.

In conclusion, the Catholic Church’s claim to doctrinal infallibility stands firmly on scriptural, historical, and theological foundations. Christ’s promises to His Apostles, the guidance of the Holy Spirit, and the unbroken chain of apostolic succession affirm that the Church is not merely a human institution but a divinely guided custodian of truth. Without this charism, the Church would fail in her mission to preserve the integrity of Christ’s teachings, ensure the unity of faith, and safeguard the faithful from error. The principle of infallibility is not a tool of overreach but a necessary means by which the Church fulfills her divine commission. It preserves the coherence of doctrine, provides certainty amidst moral and theological ambiguity, and manifests Christ’s enduring presence in the life of the Church. As the “pillar and bulwark of the truth," the Church’s infallibility is not an imposition but a gift, enabling her to proclaim the Gospel with unwavering fidelity and authority until the end of time. Thus, the Catholic Church’s claim to infallibility is not only consistent with Christ’s promises but essential to the fulfillment of her mission to teach, sanctify, and govern in His name. This assurance of truth, safeguarded through divine assistance, remains a profound testimony to the Church’s unique and enduring role in the salvation of souls.

FINAL REMARKS.

Thank you to all the readers who have made it this far. Your engagement with this debate reflects your dedication to exploring these important questions about faith, history, and theology. It is my hope that this discussion has provided you with valuable insights, whether you agree with my position or not. Ultimately, the purpose of any debate is not merely to win an argument but to deepen our understanding and seek the truth together.

I deeply appreciate your willingness to consider this perspective and the time you have invested in following this exchange. Your thoughtful consideration is what makes this debate meaningful, and for that, I am sincerely grateful.
Con
#2
Framework:
Catholic Claims to Infallibility
The Catholic Church makes a number of claims to infallibility. The first is that the Pope cannot err when he speaks ex cathedra. The second is that binding statements on faith and morals made by ecumenical councils are infallible when approved by the pope. A third is that if all bishops around the world agree on a teaching, it is infallible.

In R1, Pro hints at the second and third claims but doesn’t defend the primacy of the pope or the infallibility of ex cathedra statements, which are necessary to distinguish the Catholic Church’s claims of being the “one true church” from the opposing claims made by the Eastern Orthodox Church. These churches disagree on essential doctrine, so if Pro cannot show that the Catholic Church is more correct than the Orthodox Church, then they have not demonstrated that the Catholic Church is infallible.

Burdens
I hold that we ought to reject claims of infallibility unless Pro can provide strong evidence for them. First, because plenty of groups and denominations have teachings that contradict the Catholic Church (and since they can’t all be right, the odds are against any individual claim). Second, because infallibility implies that it is impossible for the Catholic Church to make an error—if it’s possible for the Catholic Church to be wrong on this issue or others, they aren’t infallible.

In this debate, Pro has the difficult task of establishing that the pope, bishops, and ecumenical councils are infallible in certain cases, even though individual church authorities fall into error all the time, as admitted by the Catholic Church itself and evidenced by history. Hence, unless Pro can show the three claims of infallibility made by the Catholic Church to be true, the Catholic Church should be assumed to not be infallible. My burden is to argue that we do not have a strong reason to believe in the infallibility of the Catholic Church, which would mean the most likely case is that it is not infallible.


1. “Scriptural Basis for Infallibility”:
“I am with you always, to the end of the age”/“When the Spirit of truth comes, he will guide you into all the truth”/“Where the Church is, there is also the Spirit of God”
God does promise to be present with the church, but this is a promise he makes to all believers, not just church authorities (Matthew 18:20). The “spirit of truth” refers to the Holy Spirit, which Jesus promises to all those who ask for it (Luke 11:13). It’s also not a guarantee of infallibility, since in the early church, Christians (including church authorities) fell into error (Galatians 2), while in the later church they split apart due to differences in doctrine. If having the Holy Spirit makes one infallible, then every Christian is infallible. That can’t be the case, since many Christians disagree on doctrine.

“obedience of faith”/“Whoever listens to you listens to me, and whoever rejects you rejects me.”/“when you received the word of God that you heard from us, you accepted it not as a human word but as what it really is, God’s word”
It’s true that the apostles were generally given authority to teach and were meant to communicate the words of God. But this does not mean that every statement made by the apostles all the time was automatically doctrinally accurate. Note that not even the Catholic church believes that the statements made by its leaders are infallible all of the time or even most of the time—they only claim infallibility for certain proclamations, such as those made at ecumenical councils. We should also note that the verses Pro is citing are about day-to-day teaching and not about ecumenical councils.

If the authority given to church leaders here isn’t sufficient for infallibility in 99% of day-to-day operations (something even the Catholic church acknowledges), then we don’t have a basis for assuming that it is sufficient for infallibility at ecumenical councils. This general authority given to the apostles is very different from the unique infallibility that the Catholic Church claims exists at ecumenical councils.

“the household of God, which is the church of the living God, the pillar and bulwark of the truth”
In context, Paul is writing here about how church authorities ought to behave, not how they do behave all the time (1 Timothy 3). He writes that bishops “must be above reproach,” not that they are. He writes that deacons “must hold fast to the mystery of the faith with a clear conscience,” not that they are guaranteed to always hold properly to the faith or guaranteed not to fall into error.

The church includes all followers of Christ, not just authorities, and not just during ecumenical councils or ex cathedra declarations. And despite the church being established as a bulwark of truth, members of the church have fallen into error and widespread corruption, a fact that even the Catholic Church has acknowledged. Even the Council of Trent acknowledged that widespread corruption existed in the church, something that even plagued its top members at times. The point is that if church members can err despite being part of the church, we ought not assume that ex cathedra statements or ecumenical councils are infallible just because they are part of the church.


2. “Historical Evidence for Infallibility”:
Pro includes citations from the Church Fathers as evidence for infallibility. Before investigating these citations, we should note that the Church Fathers themselves were not infallible. Origen, for example, had a number of beliefs that are widely considered erroneous today, even by the Catholic Church. But that said, I do think the Church Fathers give some insight into the church at their time period. For that reason, their writings are at least worth looking at.

Apostolic Succession:
While several early Church Fathers did in fact value a clear line of succession, what we don’t see in these citations is a specific claim of infallibility, much less mentions of ex cathedra statements or church councils being particularly infallible. It’s easy to see why a clear line of succession is important when many heresies are being taught elsewhere, since successors of the apostles are more likely to be privy to correct doctrine. Not to mention, this was a time when literacy rates were low and most Christians couldn’t read the Bible. Succession was given as a reason that teachings made by these teachers were more likely to be accurate, not that they were guaranteed to be accurate.

“those who, as I have shown, possess the succession from the apostles; those who, together with the succession of the episcopate, have received the certain gift of truth”
The Holy Spirit is the spirit of truth, but not even those with the Holy Spirit are granted infallibility. In addition to the apostles themselves not being infallible (Peter denied Jesus three times), their successors were considered to have a lesser authority than they. St. Ignatius himself wrote, “I do not, as Peter and Paul, issue commandments unto you. They were apostles; I am but a condemned man.” He also leaves open the possibility of church leaders falling into error, referring to “those who are involved in many errors” and those who “misunderstood what Paul has spoken.” He even speaks of “those who are believed to be presbyters by many, but serve their own lusts, and, do not place the fear of God supreme in their hearts,” saying that they “shall be convicted by the Word, who does not judge after outward appearance, nor looks upon the countenance, but the heart.” He compares leaders who fall into corruption to the elders in Israel who fell into corruption. Clearly, truth does not depend on the office of bishop or any other office—authorities can fall into error despite outwardly appearing important.

Hence, this was not given as a guarantee that church successors would never err or a reason to believe that Catholic successors are infallible in particular. Baptists, Lutherans, Orthodox, and others all follow their interpretations of the scriptural writings of the apostles, and a Catholic bishop emerging from a long chain of succession millenia after the early church is not guaranteed to have a better interpretation of scriptures that almost anyone can access at this point. Even early on, the weaknesses of relying solely on authorities became clear when corrupt practices like simony emerged in the church during the Middle Ages. Being a descendant of the apostles does not guarantee immunity from error.

“one, holy, catholic, and apostolic”:
The term “catholic” was indeed used to refer to the early church, but at that time it meant the same thing as “orthodox” or “universal.” The fact that the Catholic church is called catholic today, even by non-Catholics, or that the Orthodox church is called orthodox, even by non-Orthodox Christians, isn’t an agreement that either of them is the “one true church,” it’s just a matter of necessity since we have to call them something.

That is to say, this term in the Nicene creed isn’t singling out the Catholic church as we know it today. Other groups like the Orthodox church claim to be the “one true church,” though a more likely interpretation is that the church is one and holy in that it is united as a body of believers in Christ, even if different groups disagree on doctrine. Most denominations are apostolic to the extent that they follow the teachings of the early apostles.

“Tertullian…ridicules the suggestion that the universal teaching of the Church can be wrong”
The standard of universal agreement doesn’t apply to the Catholic Church’s claims of infallibility. Orthodox, Lutheran, and other Christian groups disagree on some or all of these points. Church councils were called to resolve widespread disagreement within the church and often led to schisms or persecution of minority sects. To claim that their teachings are universal, the modern Catholic church holds that their authority makes them infallible, even though they believe the authority given to church leaders in other denominations doesn’t imply infallibility. It’s a big stretch to say that special infallibility is given to some leaders but not others, since all believers are promised the Holy Spirit (Luke 11:13).


3. Authority ≠ Infallibility:
Pro’s citations from the early church and scripture don’t use the term “infallibility” to describe church leaders. Instead, they argue that the apostles and their successors have some level of authority. The gap between authority and infallibility is bigger than it might seem at first glance. Many authorities or chosen leaders are selected in the Bible to carry out God’s commands, yet all of them were flawed and none of them infallible the way that Jesus was. If an authority gives an opinion or a declaration about doctrine, we should take into account not just their authority but how reliable they have been in the past, the likelihood of corruption, and their justification for said belief. Likewise, when the Church and its leaders are said to be authoritative, this does not imply infallibility. Authority is given for general, day-to-day scenarios, not as a basis for infallible pronouncements on doctrine.

Moses
The Lord tells Moses to give Joshua “some of your authority, so that all the congregation of the Israelites may obey” (Numbers 27). Clearly, Moses had authority, enough to expect obedience from the Israelites. Yet he still fell into error and was punished by not being allowed into the Promised Land (Numbers 20).

King Saul
Saul was God’s anointed king (Samuel 24), and the Lord said that “[Saul] will rule over my people.” (Samuel 9). Despite this, Saul fell into error many times, trying to murder David and disobeying commandments.

Sanhedrin
The Sanhedrin was assembled by Moses and established as an authority by God. He even tells Moses that he will “take some of the spirit that is on you and put it on [the Sanhedrin]” (Numbers 11). Yet they erroneously found Jesus guilty of blasphemy and handed him over to the Romans for execution (Matthew 26). Much like modern ecumenical councils, a council composed of fallible individuals is not guaranteed to suddenly become infallible. It’s important to note that Iraneus himself compares the authority given to Old Testament leaders to the authority given to leaders of the church—and this authority clearly does not guarantee infallibility.

Parents and Children
Children are told to obey their parents (Ephesians 6), but this does not mean that any parent who makes a confident statement on doctrine is correct in doing so. In the Old Testament, the nation of Israel, including many parents, fell into error numerous times.

Apostles and Church Leaders
Despite Peter the apostle being used by Catholics as a basis for the infallibility of the Catholic church, Peter himself denied Jesus three times (Matthew 26). Furthermore, he fell into hypocrisy for a brief period, leading the other Jews, and even Barnabas, astray (Galatians 2).

“Without this charism, she could not protect her faithful from doctrinal error or fulfill Christ’s command to teach all nations with authority”/”Without this charism, the Church would fail in her mission to preserve the integrity of Christ’s teachings”
We could certainly say similar things of the Kings of Israel or the Sanhedrin, of Moses and of many parents. Throughout the Bible, we repeatedly see chosen authorities fall into error and fail to meet a given task set out for them. Moses disobeyed commands, Peter denied three times Jesus and fell into hypocrisy for a time, and most of the Kings of Israel were bad. Even the most righteous of these men was not guaranteed infallibility.


4. Church Authorities Have Fallen into Error:
It’s not really a point of dispute, even among Catholics, that church authorities (even in significant numbers) have erred many times. The sources Pro provides imply that successors of the apostles are given some amount of authority, but not even Catholics consistently hold that this alone guarantees infallibility.

Succession from Apostles in Multiple Churches
Lutheran bishops and Orthodox bishops can also claim a line of succession from the early apostles. The latter is even recognized by Catholics! Nonetheless, they disagree on many points of doctrine, hence the resulting schisms.

The Catholic church does deny the Lutheran claim to apostolic succession, conditioning the right to succession on agreement with Catholic authorities, but this condition is not present in the sources Pro provides from the early church. The early church fathers note that the apostles appointed successors who had authority (but who, as we can see, were capable of falling into error.) The additional proclamation that church authorities and councils are infallible under certain circumstances was a later Catholic invention and only fully formalized at the First Vatican Council in 1868.
Round 2
Pro
#3
INTRODUCTION.

I want to extend my heartfelt gratitude to Savant for publishing such an illuminating and thorough analysis. Your intellectual rigor and dedication to engaging deeply with these important ideas exemplifies the kind of thoughtful discourse our world needs. The time, care and scholarship you've invested has meaningfully advanced the conversation and given us all valuable new perspectives to consider.

PREREQUISITE.

My opponent claims that unless I defend all three forms of Catholic infallibility (Papal ex cathedra statements, ecumenical councils, and universal episcopal agreement), my case is incomplete. They argue the Catholic Church must distinguish itself from other claimants like the Eastern Orthodox Church. For this reason, I'd like to clarify the scope of the debate, as articulated by the debate's description.

This debate is about the general principle of infallibility. While uncovering the basis for all three forms of infallibility is important, this debate focuses on whether the Catholic Church possesses infallibility in principle, as promised by Christ and demonstrated historically. The specific mechanisms of the forms of infalliblity do not negate the broader scriptural and historical foundations for the Catholic claim to infallibility. I'd also like to point out that rejecting infallibility because other groups claim authority, as my opponent argues, is fallacious. The existence of competing claims does not diminish the evidence for Catholic infallibility. Truth is not determined by the number of claimants but by the weight of scriptural and historical evidence. If competing claims disproved truth, no religious group could claim authority.

COUNTER-ARGUMENTS.

Scriptural Basis.

God does promise to be present with the church, but this is a promise he makes to all believers, not just church authorities (Matthew 18:20). ... Jesus promises [the Holy Spirit] to all those who ask for it (Luke 11:13). It’s also not a guarantee of infallibility, since the early church ... fell into error (Galatians 2), while the later church split apart due to differences in doctrine.
Christ’s promise of the Spirit of Truth (John 16:13) and His presence "to the end of the age" (Matthew 28:20) were given directly to the Apostles in the context of their teaching mission. Let's examine the contextual difference in Christ's promises. The specific promises in John 14-16 were made to the Apostles in their unique teaching capacity. Note the context: these promises were made at the Last Supper specifically to the Apostles, not to all believers. Christ singles them out for a special teaching role: "Whoever listens to you listens to me," (Luke 10:16). This promise connects directly to their commission to teach "all nations" (Matthew 28:19-20). The distinction becomes clearer when we examine Acts 15, where the Apostles gathered to make binding doctrinal decisions. They prefaced their decree with "it has seemed good to the Holy Spirit and to us" (Acts 15:28) — claiming a unique corporate teaching authority different from individual spiritual guidance. This model of authoritative council, guided by the Spirit to resolve doctrinal disputes, demonstrates exactly how the Church's teaching office differs from individual spiritual guidance. Thus, Acts 15 and John 16 demonstrate the Apostles' unique teaching authority, distinct from individual guidance.

My opponent's argument about Galatians 2 actually supports the Catholic position. Peter's error there was in personal conduct (hypocrisy in table fellowship), not in teaching doctrine. As stipulated in the description of the debate, infallibiliy is the Church's impossiblity of failing into error in the final decision on doctrines concerning faith and morals. Peter's personal sin is not a decision on doctrine concerning faith and morals. This perfectly illustrates the Catholic distinction between personal fallibility and official teaching infallibility. No Catholic claims that having the Holy Spirit makes individuals, even Popes, personally infallible in all actions. Rather, the Spirit guarantees that the Church's definitive teachings on faith and morals, when properly exercised through established channels (councils, ex cathedra statements), are preserved from error. The fact that Christians disagree on doctrine reinforces, rather than undermines, the need for an infallible teaching authority. Without it, we're left with competing interpretations and no way to definitively resolve doctrinal disputes. This is precisely why Christ established a teaching authority that could speak definitively on matters of faith and morals — not to make every believer infallible, but to provide a sure guide amid competing claims.

Over the course of their round, my opponent attempts to use the logic of "presonal sin negatives doctrinal infallibility" in many arguments. Watch out for those as you keep reading this round.


It's true that the apostles were generally given authority to teach and were meant to communicate the words of God. But this does not mean that every statement made by the apostles all the time was automatically doctrinally accurate
This reasoning is another instance of "personal sin negatives doctrinal infalliblity." Catholic doctrine recognizes human frailty while affirming that the Holy Spirit prevents error in definitive doctrinal proclamations (i.e., Acts 15:28, where the Apostles' council reached an authoritative decision guided by the Spirit). When Jesus declares, "Whoever listens to you listens to me" (Luke 10:16), He equates the Apostles' teaching with His own. Similarly, Paul's affirmation that the Church is the "pillar and bulwark of the truth" (1 Timothy 3:15) implies a divinely protected teaching authority, as the truth cannot be upheld by a fallible institution in definitive matters of faith and morals.

My opponent's argument misunderstands the relationship between general teaching authority and specific instances of infallible pronouncement. The fact that not all teaching acts are infallible doesn't undermine the existence of specific infallible acts — rather, it highlights the careful distinctions the Church makes about when and how infallibility operates. Consider an analogy to the Biblical authors: not every word spoken by Paul or Peter was divinely inspired, yet under specific conditions (writing Scripture), they produced infallible teaching. The Church has always recognized this distinction — that God's guarantees of truth operate in specific ways under specific conditions.

My opponent's argument that "if authority isn't sufficient for everyday infallibility, it can't be sufficient for council infallibility" fails to recognize that different acts of teaching authority can have different levels of divine guarantee. Just as a judge may have general judicial authority but only certain rulings become binding precedent, the Church's teaching authority operates at different levels for different purposes. The verses about Christ's promises of the Spirit's guidance do apply to councils precisely because councils represent the Church's highest exercise of teaching authority — the moment when the successors of the Apostles gather specifically to define doctrine for the universal Church. This isn't a "different" authority from day-to-day teaching; it's the same authority exercised in its most solemn and complete form. This understanding preserves both the general teaching authority of the Church and the special character of infallible pronouncements, without creating an artificial division between them. It's not that councils have a "different" authority — they represent the full exercise of the authority Christ gave the Apostles, under the conditions where His promises of preserving truth apply most fully.


In context, Paul is writing here about how church authorities ought to behave, not how they do behave all the time (1 Timothy 3). He writes that bishops "must be above reproach," not that they are. He writes that deacons "must hold fast to the mystery of the faith with a clear conscience," not that they are guaranteed to always hold properly to the faith or guaranteed not to fall into error.
My opponent's interpretation of 1 Timothy 3:15 misses the crucial distinction between individual officeholders and the Church as a divine institution. When Paul calls the Church "the pillar and bulwark of the truth," he's making an ontological statement about the Church's nature and divine purpose, not merely prescribing ideal behavior for its members. Let's examine the context more carefully: The description "pillar and bulwark of truth" modifies "the church of the living God" directly, not individual bishops or deacons. While the surrounding verses do discuss requirements for church officers, verse 15 shifts to describing the Church's essential nature. The Greek text uses the present indicative "estin" ἐστὶν ("is") rather than any form suggesting "ought to be." Paul is stating what the Church fundamentally is, not what it aspires to be. The metaphors "pillar" (stylos, στῦλος) and "bulwark/foundation" (hedraiōma, ἑδραίωμα) are architectural terms denoting essential structural elements that actually support and secure truth, not aspirational goals. A pillar either supports or it doesn't — there's no "ought to support."

The requirements for bishops and deacons actually reinforce this understanding. These requirements exist precisely because the Church is the pillar of truth — its officers must meet high standards because they serve in an institution divinely established to preserve and teach truth. Their personal failings don't negate the Church's essential nature, just as the moral failings of individual Israelites didn't negate Israel's status as God's chosen people. This aligns with how Christ established his Church: "on this rock I will build my church, and the gates of Hades (hell) shall not prevail against it" (Matthew 16:18). This is a statement of what the Church is and will be, not what it ought to be. The Church's role as truth's pillar isn't aspirational but essential to its divine constitution. When Jesus declares, "Whoever listens to you listens to me" (Luke 10:16), He equates the Apostles' teaching with His own. Similarly, Paul's affirmation that the Church is the "pillar and bulwark of the truth" (1 Timothy 3:15) implies a divinely protected teaching authority, as the truth cannot be upheld by a fallible institution in definitive matters of faith and morals.


Historical Evidence.

While several early Church Fathers did in fact value a clear line of succession, what we don't see in these citations is a specific claim of infallibility, much less mentions of ex cathedra statements or church councils being particularly infallible
This argument misunderstands how doctrine develops and how early Church Fathers expressed these concepts. While they may not have used the exact term "infallibility," their writings clearly imply this concept through their absolute assertions about the Church's teaching authority. The principle of infallibility was assumed, even if not explicitly articulated. The writings of St. Irenaeus (i.e., Adv. haer. III 3:1) affirm that apostolic succession ensures the preservation of truth: "They have received the certain charisma of truth according to the pleasure of the Father." (Adv. hae. IV. 26:4) The word "certain" (certum) implies guaranteed truthfulness, not mere probability. When he declares "Where the Church is, there is also the Spirit of God... but the Spirit is truth,"  (Adv. haer. III 24:1) he's asserting an absolute guarantee of truthful teaching, which is precisely what we mean by infallibility.

While explicit formulations of infallibility developed later (as with many doctrines), the underlying belief in the Spirit's guidance of the Church’s teaching is evident from the early Fathers. Furthermore, Tertullian's argument that it would be impossible for all churches to err because the Holy Spirit was sent specifically to be "the teacher of truth" (Tertullian, De praesc 28) directly implies infallibility. He's not suggesting the Spirit might fail in this mission. The Church's understanding of how infallibility operates developed naturally from these early beliefs about the Church's guaranteed truthfulness. This is normal doctrinal development: later formulations make explicit what was implicit in earlier teaching.


The Holy Spirit is the spirit of truth, but not even those with the Holy Spirit are granted infallibility. ... St. Ignatius himself wrote, "I do not, as Peter and Paul, issue commandments unto you. They were apostles; I am but a condemned man." He also leaves open the possibility of church leaders falling into error, referring to "those who are involved in many errors" and "misunderstood what Paul has spoken." ... Clearly, truth does not depend on the office of bishop or any other office—authorities can fall into error despite outwardly appearing important.

Hence, this was not given as a guarantee that church successors would never err or a reason to believe that Catholic successors are infallible in particular. ... Being a descendant of the apostles does not guarantee immunity from error.
My opponent's argument fundamentally misunderstands the Catholic doctrine of infallibility by conflating personal sinlessness with the Church's teaching authority. This is another instance where my opponent attempts to argue "personal sin negatives doctrinl infallibility." The fact that Peter denied Christ or that bishops can sin does not negate the Church's infallibility in defining doctrine. The fault was not that he taught error of doctrine, but that he sinned in conduct. Inspiration, though it kept the apostles from teaching error, did not keep them necessarily from sin. The Church's infallibility pertains specifically to official teaching on faith and morals, not to the personal behavior of her ministers. When St. Ignatius says "I do not, as Peter and Paul, issue commandments unto you," (Ep. Ign. Rom. 4) this expresses personal humility, not a theological statement about the limits of episcopal authority. His recognition of personal unworthiness actually strengthens the Catholic position by demonstrating that the Church's teaching authority transcends the personal qualities of her ministers. Christ's promise that "the gates of Hades (hell) shall not prevail" against His Church (Matthew 16:18) guaranteed not the sinlessness of her ministers but the preservation of true doctrine, as St. Irenaeus explains: "For where the Church is, there is the Spirit of God; and where the Spirit of God is, there is the Church and every kind of grace" (Adv. haer. III 24:1). My opponent's citation of medieval corruption like simony again conflates moral conduct with doctrinal teaching. Notably, even during periods of serious moral corruption, the Church's doctrinal definitions remained orthodox. This paradox actually demonstrates the Holy Spirit's protection — despite human weakness, the Church's teaching remained uncorrupted, fulfilling Christ's promise to guide her "into all truth" (John 16:13).

Regarding multiple churches claiming apostolic succession, Catholic teaching has always held that valid succession requires both unbroken sacramental succession through valid ordination and continuity of doctrine with the apostolic faith. This is why Tertullian challenged heretics to "show the origins of their churches, let them unroll the order of their bishops, running down in succession from the beginning" (De Praes. 32). The Catholic Church alone maintains both unbroken succession and doctrinal continuity with the apostolic age.


The standard of universal agreement doesn't apply to the Catholic Church's claims of infallibility. Orthodox, Lutheran, and other groups disagree on some or all of these points. Church councils were called to resolve widespread disagreement and often led to schisms ... . To claim that their teachings are universal, the ... Catholic Church holds that their authority makes them infallible, even though ... the authority given to leaders in other denominations doesn't imply infallibility. It's a big stretch to say that special infallibility is given to some leaders but not others, since all believers are promised the Holy Spirit (Luke 11:13).
My opponent's argument about universal agreement and denominational disagreement misunderstands both the historical development of doctrine and the nature of Catholic authority. Their position confuses the universal character of truth with universal acceptance of truth, while simultaneously misapplying the promise of the Holy Spirit. The Catholic Church's claim to infallibility does not rest on universal contemporary agreement but on Christ's establishment of a specific teaching authority. When Jesus gave Peter the keys of the kingdom (Matthew 16:19), promising that whatever he bound on earth would be bound in heaven, He established a concrete authority — not a democratic consensus. The fact that later groups disagreed with Catholic teaching no more invalidates this authority than the existence of Arians invalidated the Council of Nicaea's teaching on Christ's divinity. St. Vincent of Lerins addressed this precisely: the Catholic faith is "what has been believed everywhere, always, by all" (Commonitorium 2:6) — referring not to contemporary universal agreement but to the consistent teaching tradition from the apostolic age.

Regarding the promise of the Holy Spirit to all believers (Luke 11:13), this demonstrates precisely the distinction between personal guidance and teaching authority. While all believers receive the Spirit for personal sanctification, Christ specifically gave teaching authority to the Apostles and their successors: "Whoever listens to you listens to me," (Luke 10:16). St. Clement of Rome, writing around 96 AD, already understood this distinction: "The apostles received the Gospel for us from the Lord Jesus Christ; Jesus Christ was sent forth from God. So then Christ is from God, and the apostles are from Christ" (1 Clement 42:1-2). This hierarchical transmission of authority explains why the early Church consistently recognized the unique teaching role of apostolic succession, even while acknowledging the Holy Spirit's work in all believers.

My opponent also argues that infallibility has shown itself to be a failure, since, in the first place, it has not prevented occurrence of schisms. The purpose for which Christ endowed the Church with infallibility was not to prevent the occurrence of schisms and heresies, which He foresaw and foretold, but to take away all justification for their occurrence; men were left free to disrupt the unity of Faith inculcated by Christ in the same way as they were left free to disobey any other commandment, but heresy was intended to be no more justifiable objectively than homicide or adultery.


Authority vs. Infallibility.

 Many authorities or chosen leaders are selected in the Bible to carry out God's commands, yet all of them were flawed and none of them infallible the way that Jesus was. If an authority gives an opinion or a declaration about doctrine, we should take into account not just their authority but how reliable they have been in the past, the likelihood of corruption, and their justification for said belief. Likewise, when the Church and its leaders are said to be authoritative, this does not imply infallibility.
In this section, my opponent argues that having authority does not imply infallibility, using examples like Moses, Saul, and the Sanhedrin to show that divinely appointed leaders often erred, arguing that "human sin negates doctrinal infallibility." Human sin, including simony and other abuses, does not negate the Spirit's guidance in preserving doctrine. Infallibility ensures that definitive teachings on faith and morals are free from error, not that Church leaders are sinless. Despite historical schisms (i.e., Great Schism, Reformation), the Catholic Church has maintained unity in essential teachings, such as the divinity of Christ and the Trinity, through the guidance of the Holy Spirit. This continuity underscores the Church's infallible teaching authority.

My opponent's comparison between biblical authorities and Church infallibility creates a false equivalence that ignores crucial theological distinctions. While Moses, Saul, and the Sanhedrin were indeed given authority for specific purposes, the Church's authority stems from Christ's explicit promises regarding doctrinal preservation: "When the Spirit of truth comes, he will guide you into all truth" (John 16:13). This is qualitatively different from the administrative or temporal authority given to Old Testament figures. As St. Thomas Aquinas explains, the Church's infallibility is not based on the personal qualities of her leaders but on Christ's promise and continuing presence: "The Church Universal cannot err, since she is governed by the Holy Ghost, Who is the Spirit of truth" (Summa Theologica, II-II, Q.1, A.9). My opponent's criteria of past reliability and corruption mistakes the instrumental cause (fallible human leaders) for the efficient cause (the Holy Spirit's guidance) of Church teaching authority.


Much like modern ecumenical councils, a council composed of fallible individuals is not guaranteed to suddenly become infallible.
This is quite true in reference to natural knowledge and would also be true as applied to Church authority if Christianity were assumed to be a mere product of natural reason. However, we set out from an entirely different standpoint. We assume, as previously and independently established, that God can supernaturally guide and enlighten individuals or groups. This divine guidance allows them, despite the inherent fallibility of human intelligence, to speak with certainty in His name and under His authority. Consequently, their words may be not only infallible but also inspired. In the first round, this was a major theme discussed: despite human fallibility, infallibility is guaranteed under the jurisdiction of the Holy Spirit. Insofar as the Holy Spirit is responsible for Church teaching, that teaching is necessarily infallible. What the Spirit of truth guarantees cannot be false.

CONCLUSION.

The evidence presented affirms that the Catholic Church's claim to infallibility is both scripturally grounded and historically consistent. My opponent's arguments misinterpret the nature of infallibility, conflating it with personal sinlessness and failing to address its defined scope: the protection of definitive teachings on faith and morals. Scriptural promises of guidance (John 16:13; Matthew 16:18) and historical examples (Acts 15) demonstrate a divinely instituted teaching authority distinct from individual fallibility. The continuity of doctrine, despite human failings and schisms, underscores the Church’s unique role as the "pillar and bulwark of the truth" (1 Timothy 3:15). Thus, the Catholic Church stands alone in its claim to infallibility, fulfilling Christ's promises to preserve His truth for all generations.
Con
#4
Thanks, CatholicApologetics.

Framework:
Pro does not dispute my R1 statement that “infallibility implies that it is impossible for the Catholic Church to make an error—if it’s possible for the Catholic Church to be wrong on this issue or others, they aren’t infallible.” That reason alone should be enough to reject claims of infallibility unless Pro can provide evidence for them beyond a reasonable doubt.

“This debate is about the general principle of infallibility…this debate focuses on whether the Catholic Church possesses infallibility in principle.”
But what does “infallibility in principle” mean, specifically? Which authorities specifically are “the church” in the context of making definitive statements on faith and morals? I’ve outlined what that means by citing actual Catholic teaching. Pro continues to argue for broadly defined infallibility, but the Catholic Church makes specific claims about times when it cannot err; specifically, when the pope speaks ex cathedra, during ecumenical councils, and in cases when all bishops around the world agree on a teaching. If the Catholic Church is wrong about any of those claims, it would be fallible by definition, or capable of being wrong.

“The existence of competing claims does not diminish the evidence for Catholic infallibility.”
I didn’t say that competing claims make Catholic infallibility impossible, just that in the absence of strong evidence for infallibility, the evidence is against any individual contradictory claim. Since many denominations make claims that contradict each other (Lutherans, Orthodox, Roman Catholic, Anglican, etc.) the odds are against any individual claim being the right one in the absence of evidence (without evidence, I have as much reason to believe one group is right as any other). If I guess from a dozen options on a multiple choice test, I’ll probably be wrong. The odds of picking the right answer increase once I have strong evidence supporting it, but my point here is that without strong evidence for Catholic infallibility, the most likely case is that the Catholic Church is not infallible.

Burdens
To win, my opponent must show that there is strong evidence for Catholic infallibility, enough to outweigh all the competing claims and the evidence that church authorities aren’t infallible at all, even as a collective. For me to win, I can either show that there are good reasons to believe the Catholic Church isn’t infallible, or that there aren’t strong reasons to believe that it is. (Though I intend to do both.)

My Case
As laid out in R1, my case has two main points: first, we don’t have strong evidence for Catholic infallibility, so we ought to believe the Catholic Church is not infallible. Second, we have good reasons to believe the Catholic Church isn’t infallible, such as other authorities not being infallible, even when acting as a group (the Sanhedrin), and apostolic successors disagreeing with each other and splitting into competing groups.


1. “Scriptural Basis for Infallibility”:
“Christ’s promise of the Spirit of Truth (John 16:13) and His presence "to the end of the age" (Matthew 28:20) were given directly to the Apostles in the context of their teaching mission…The specific promises in John 14-16 were made to the Apostles in their unique teaching capacity…these promises were made at the Last Supper specifically to the Apostles, not to all believers.”
Yes, I agree that Jesus promises his presence to the apostles in the context of their teaching mission, and at other times. Those specific verses are directed at the apostles. My point is that Jesus makes similar promises to all believers at other times. Pro does not dispute that Jesus promises his presence to all believers in Matthew 18:20. Pro does not dispute that Jesus promises the Holy Spirit (i.e. the Spirit of Truth), to all those who ask for it in Luke 11:13. If everyone with the spirit of truth is infallible, then all Christians are infallible, and not even the Catholic Church believes that all believers are infallible. So having the spirit of truth or the presence of God ≠ infallibility.

“Christ singles them out for a special teaching role: "Whoever listens to you listens to me," (Luke 10:16). This promise connects directly to their commission to teach "all nations" (Matthew 28:19-20).”
Jesus says this to Judas too, this is right before he says that “one of you will betray me” (John 13:21). Clearly Judas was not infallible. This promise is about cases where the apostles correctly repeat the doctrine Jesus told them, since it’s said in the context of “proclaiming the good news” (Matthew 10); it’s not saying that the apostles cannot fall into error. Peter even warns of false prophets who “deny the master who brought them” (2 Peter 2), implying that authorities can fall into error. This verse doesn’t bring up ecumenical councils or the other cases where the Catholic Church claims infallibility—it’s made to people who are clearly capable of error. Since bishops can fall into heresy and give false teaching outside of ecumenical councils, why should we assume that they are infallible during those councils? Christ’s promise here doesn’t mention those councils at all.

“The distinction becomes clearer when we examine Acts 15, where the Apostles gathered to make binding doctrinal decisions. They prefaced their decree with "it has seemed good to the Holy Spirit and to us" (Acts 15:28)...Acts 15 and John 16 demonstrate the Apostles' unique teaching authority, distinct from individual guidance.”
Of Pro’s citations, this one comes closest to referencing the specific claims made by the Catholic Church, yet it doesn’t actually establish (or even imply) that ecumenical councils are infallible. A council making a good decision at some point, as referenced here, does not mean that councils can never err. King David made the correct decision to defeat Goliath (1 Samuel 17), but he was not infallible. The Sanhedrin was put together by Moses (Numbers 11) and almost certainly made some good decisions, yet they were not infallible and accused Jesus of blasphemy. Since all believers are guided by the Holy Spirit (Luke 11:13) but are not infallible, giving an example of a council that was guided by the Holy Spirit and made a good decision does not imply infallibility. Pro describes this as “binding,” but the verses say nothing about infallibility, even if we do accept that this particular decision about food sacrificed to animals was a good one. Furthermore, accepting this teaching from the apostles as accurate and permanent contradicts Catholic teaching, as the apostles say “it has seemed good to the Holy Spirit and to us to impose on you no further burden than these essentials.” The Catholic Church imposes additional burdens on its members, such as telling them they must observe the Eucharistic fast.

“Peter's error there was in personal conduct (hypocrisy in table fellowship), not in teaching doctrine…Peter's personal sin is not a decision on doctrine concerning faith and morals… another instance of "personal sin negates doctrinal infallibility."”
Peter swore that he had never met Jesus (Matthew 26), which is a false statement made about the most important person in Christian doctrine…furthermore, Peter’s error in Galatians comes very close to erroneous teaching, since “other Jews joined him in this hypocrisy, so that even Barnabas was led astray” (Galatians 2:13). We can assume that Peter either explicitly or implicitly communicated wrong behavior to the others. Pro cedes this as a mistake on Peter’s part but states that “personal sin does not negate doctrinal infallibility.” But here’s where it does pose problems for Catholic infallibility. We’ve established that leaders are given the charism of truth, promises of authority, the Holy Spirit, etc. Yet they still make mistakes. These guidelines don’t keep them from lying, from being hypocritical, from betraying Jesus and sending him to his death, from engaging in behaviors that the Catholic Church later apologized for, from teaching falsely on topics other than faith and morals, or from teaching falsely on faith and morals outside of a council. Given all that, it seems like a safe assumption that these guidelines aren’t a promise of infallibility at all. Pro and the Catholic Church want us to read these verses and assume that bishops are infallible during ecumenical councils specifically, when none of the verses is implying infallibility or attributing special authority to councils.

“No Catholic claims that having the Holy Spirit makes individuals, even Popes, personally infallible in all actions. Rather, the Spirit guarantees that the Church's definitive teachings on faith and morals, when properly exercised through established channels (councils, ex cathedra statements), are preserved from error.”
Yet most of the citations by my opponent don’t even reference these “established channels,” and of those that do, none of them say that authorities cannot err when they act through said channels. Apostles and believers have the Holy Spirit, presence of God, certain charisma of truth, etc. all the time, but they are not infallible all the time. If a Catholic bishop made a definitive statement about faith and morals outside of these channels, not even the Catholic church would accept it as infallible. So we can definitively say that having the Holy Spirit, presence of God, certain charisma of truth, etc. when making a statement about faith and morals does not equal infallibility. For scripture to support Catholic claims to infallibility, it would have to say that authorities are perfectly guarded from error specifically when the pope speaks ex cathedra, during ecumenical councils, and in cases when all bishops around the world agree on a teaching. Scripture doesn’t say that; as I pointed out in R1, this was a later Catholic invention and only fully formalized at the First Vatican Council in 1868.

“The verses...apply to councils precisely because councils represent the Church's highest exercise of teaching authority…it's the same authority exercised in its most solemn and complete form.”
But councils aren’t directly mentioned in these verses as free from error. They give general authority to church leaders (which isn’t the same as infallibility.) Arguing that church councils are a higher form of authority doesn’t make them infallible. The Sanhedrin was a high form of authority, yet it still erred in condemning Jesus as a blasphemer (Matthew 26). Ecumenical councils are composed of individuals whom we agree are fallible, and these verses don’t indicate that this fallibility vanishes when multiple individuals meet together—Pro claims it does, but that’s a teaching of the modern Catholic Church, not something taken from these verses.

“Paul calls the Church "the pillar and bulwark of the truth,"…Christ's promise to guide her "into all truth" (John 16:13)”
Note that the church is made up of all believers, not just authorities present during councils. Furthermore, Paul calls the church the “pillar of truth” since it was given Jesus’ teachings. This does not mean the church can never err. The library is a “bulwark of truth” even if some library books contain incorrect information, even if many textbooks contain the same common incorrect claim. Paul’s analogy here is a general metaphor about the church receiving Jesus’ message, not a guarantee of infallibility. Jesus promises to guide the church toward truth with the Holy Spirit and the gospel, but this does not mean that fallible humans will never err or make mistakes. This is why Peter and Barnabus fell into hypocrisy and as Pro acknowledges, no individual is “personally infallible in all actions.” So despite being a pillar and bulwark of truth, church authorities, even those at the top, can err, falling into hypocrisy, teaching heresies, allowing widespread misdeeds and allowing the sin of simony to flourish on a large scale. This is why Ignatius speaks of “those who are believed to be presbyters by many, but serve their own lusts, and, do not place the fear of God supreme in their hearts,” saying that they “shall be convicted by the Word, who does not judge after outward appearance, nor looks upon the countenance, but the heart.” Again, he compares leaders who fall into corruption to the elders in Israel who fell into corruption. Clearly, truth does not depend on the office of bishop or any other office—authorities can fall into error despite outwardly appearing important. Being a bulwark of truth doesn’t guarantee that church authorities won’t make any of those mistakes, so we should not assume that it prevents ecumenical councils from falling into error. None of these verses indicates that ecumenical councils or pope have a unique guarantee against error.


2. “Historical Evidence for Infallibility”:
Extend my R1 point that the Church Fathers themselves were not infallible, slipping into error at times.

“their writings clearly imply [infallibility]…The word "certain" (certum) implies guaranteed truthfulness, not mere probability… "Where the Church is, there is also the Spirit of God... but the Spirit is truth"”
The “certain truth” refers to the Holy Spirit itself, not what is taught by someone with the Holy Spirit. Origen is held in high regard, but he still slipped into error at times. And again, the Holy Spirit is given to all those who ask for it (Luke 11:13). Pro concedes that individuals are not infallible, but they claim that “the Spirit guarantees that the Church's definitive teachings on faith and morals, when properly exercised through established channels (councils, ex cathedra statements), are preserved from error.” Iraneus’ writing does not support that claim. Authority didn’t make the Sanhedrin infallible, and the Holy Spirit doesn’t make every church infallible (Anglicans, Lutherans, Catholic, Orthodox all contradict each other.) So why should we assume that the Holy Spirit does make ecumenical councils infallible? Iraneus’ quote here isn’t about ecumenical councils.

“the underlying belief in the Spirit's guidance of the Church’s teaching is evident from the early Fathers”
This is still very different from infallibility, since Lutherans, Orthodox, Anglicans, etc. could all claim guidance from the Holy Spirit.

“Tertullian's argument that it would be impossible for all churches to err because the Holy Spirit was sent specifically to be "the teacher of truth" (Tertullian, De praesc 28)”
Tertullian says that it is very unlikely for all churches to err in the same way, not impossible (“is it likely that so many churches, and they so great, should have gone astray into one and the same faith?”). If he’s appealing to probability here and not a guarantee of infallibility, that’s already contrary to the Catholic teaching on ecumenical councils. Furthermore, saying that not all churches have erred is not a guarantee that the modern Catholic church cannot err. Even during the Council of Nicea, different churches were saying different things, and some of them were wrong. Tertullian is not speaking here about ecumenical councils. Since not every church agrees with Catholic ecumenical councils or ex cathedra statements, Tertullian’s belief that it is unlikely for every church to err does not support the Catholic position.

“When St. Ignatius says "I do not, as Peter and Paul, issue commandments unto you," this expresses personal humility, not a theological statement about the limits of episcopal authority.”
He specifically references that Peter and Paul “were apostles.” Pro’s case relies on church authorities being on the same authoritative level as the apostles. Since one of their direct successors isn’t comfortable issuing commands (a show of authority), this is a good reason we shouldn’t assume all church leaders to have the same amount of authority as the apostles.

“The apostles received the Gospel for us from the Lord Jesus Christ…Christ is from God, and the apostles are from Christ" (1 Clement 42:1-2)”
We could also say that Israel is from God, or that Adam and Eve are from God, or that the Sanhedrin is from God. Yet Israel, Adam, Eve, and the Sanhedrin all fell into error at various points, as did some of the apostles. Saul and David were God’s anointed kings, but they each abused their authority many times. Despite Christ guiding the apostles into truth, not everything said by the apostles was true. As I mentioned before, Peter denied Jesus three times (Matthew 26). Again, this passage is speaking generally about the apostles, not making any statement about ecumenical councils.

“St. Vincent of Lerins…the Catholic faith is "what has been believed everywhere, always, by all"”
The infallibility of councils and ex cathedra statements is not “what has been believed everywhere, always, by all,” it’s a modern development. The word “catholic” was used to mean “universal” in the early church, not to refer to the modern Catholic Church and its claims to infallible councils.

“As St. Thomas Aquinas explains…"The Church Universal cannot err"”
Thomas Aquinas was writing in the 1200s, a millennium after the early church and well after the Catholic/Orthodox split in 1054. I could just as easily quote a contemporary Orthodox scholar rejecting papal supremacy, or Martin Luther who came only a few hundred years later. The point is, Aquinas’ writings don’t tell us what the early church believed. And even if we accepted this writing, the “church universal” has not accepted Catholic infallibility—Orthodox and Protestant churches disagree with it, not to mention Christians who were punished in Catholic or Orthodox churches for disagreeing with authorities.


3. Authority ≠ Infallibility:
“While Moses, Saul, and the Sanhedrin were indeed given authority…the Church's authority stems from Christ's explicit promises…"When the Spirit of truth comes, he will guide you into all truth" (John 16:13).”
I covered the verses on truth already, but I’ll address the analogy a bit more. God promising authority and good things for a particular group does not make it impossible for that group to err. For example, God promised that Israel would be “a kingdom of priests and a holy nation” (Exodus 19:6). And he certainly guided Israel into the truth. Yet Israel often fell into idol worship and turned away from God, including its highest authorities. Just because a person or institution will at some point accomplish good things, this does not mean there won’t be periods where some or even most of its members fall into error.


4. Church Authorities Have Fallen into Error:
“valid succession requires both unbroken sacramental succession through valid ordination and continuity of doctrine with the apostolic faith.”
Lutheran bishops and Orthodox bishops can both claim unbroken sacramental succession. The third requirement (“continuity of doctrine”) makes infallibility circular. Pro’s argument is that in order for successors to be infallible (i.e. correct), they have to teach the same doctrine taught to the apostles (i.e. correct doctrine). In order for a council to be infallible, the authorities at the council can’t be heretics. And how do we know that their teaching isn’t heresy? Supposedly, it’s because they’re infallible.

Rather than distinguishing the modern Catholic Church from Lutherans or Orthodox, Pro simply claims that “the church is infallible.” But which church, and what singles that church out from the others among the verses provided by Pro? The Catholic Church does recognize Orthodox apostolic succession, yet both churches cannot be infallible since they disagree on the authority of the pope. If we accept Pro’s case that legitimate church councils are guarded from error, this wouldn’t get us any closer to determining what makes a “legitimate” church council. If the Orthodox Church is right that papal supremacy is a false doctrine (a doctrine Pro has not defended in this debate), then the Catholic Church would be the ones inconsistent with the apostolic faith and not infallible.
Round 3
Pro
#5
INTRODUCTION.

As we approach the end of this debate, I would like to thank my opponent, Savant. Throughout this discourse, you have demonstrated unwavering dedication and an exceptional level of effort. I hope to speak on the behalf of everyone when I say that your participation has been a valuable asset. Your arguments have not only prompted critical reflection but also fostered a deeper understanding of the topic. I would like to reiterate my heartfelt gratitude for your contributions.


PREREQUISITE.

In my previous round's Prerequisite section, I have rearticulated the scope of infallibility per the debate's description: "The term refers to the Church's infallibility in the final decision on doctrines concerning faith and morals." This definition of infallibility is not limited to specific mechanisms of infallibility.

My opponent challenges the concept of "infallibility in principle" by demanding specificity regarding its mechanisms. However, this debate focuses on the broader claim: whether the Catholic Church, as the institution founded by Christ, possesses the authority and protection from error necessary to fulfill its divine mission. The mechanisms of infallibility are secondary to the principle. My opponent initially rejected narrowing down to specific mechanisms (papal infallibility) and agreed to a broader scope for this discussion (see comments), acknowledging that the focus should be on the principle of infallibility rather than narrowly on papal infallibility. Their current insistence on focusing exclusively on specific mechanisms, such as papal infallibility, contradicts the scope of this debate and their earlier position.


COUNTER-ARGUMENTS.

Framework.

Pro does not dispute my R1 statement that “infallibility implies that it is impossible for the Catholic Church to make an error—if it’s possible for the Catholic Church to be wrong on this issue or others, they aren’t infallible.”
I have disputed that notion throughout my previous round. (1) R2 Counter-Arguments, Scriptural Basis #1, (2) R2 Counter-Arguments, Historical Evidence #2, (3) R2 Counter-Arguments, Authority vs. Infallibility #1, and (4) my R2 Conclusion. My position has been consistent: infallibility pertains only to the Church's decision on doctrines regarding faith and morals. This is different than saying that the Catholic Church can never make an error.


in the absence of strong evidence for infallibility, the evidence is against any individual contradictory claim. Since many denominations make claims that contradict each other ... the odds are against any individual claim being the right one in the absence of evidence ... If I guess from a dozen options on a multiple choice test, I’ll probably be wrong. ... without strong evidence for Catholic infallibility, the most likely case is that the Catholic Church is not infallible.
My opponent's argument assumes that all claims to authority are equally unsubstantiated without evidence. However, the Catholic Church's unique claims and evidence for infallibility set it apart. The existence of multiple claims does not diminish the likelihood of truth among them — just as competing scientific theories do not negate the existence of a correct explanation. Instead, truth must be discerned through evidence. Unlike a random "guess," this debate requires careful evaluation of evidence, reason, and revelation. The Catholic Church uniquely claims an unbroken apostolic succession, tracing its authority to Christ and the apostles (cf. Matthew 16:18-19, John 20:21-23). While the Orthodox Church shares apostolic succession, it lacks universal unity due to the absence of a central teaching authority. Protestant denominations reject apostolic succession and infallibility, relying instead on sola scriptura, a doctrine lacking biblical support. Upon critical examination, the Catholic Church's claim to infallibility is uniquely substantiated by Scripture, the Early Church Fathers, and the historical continuity of its teaching authority.


Pro does not dispute that Jesus promises the Holy Spirit (i.e. the Spirit of Truth), to all those who ask for it in Luke 11:13. ... If everyone with the spirit of truth is infallible, then all Christians are infallible ... . So having the spirit of truth or the presence of God ≠ infallibility.
My opponent conflates general spiritual guidance with institutional infallibility. Christ's Holy Spirit distinguishes between individual believers' guidance and the Church's collective doctrinal authority. The Spirit's presence doesn't guarantee personal errorlessness, but ensures the Church's core theological transmission remains intact. Scriptural references demonstrate a nuanced hierarchical authority: all believers receive spiritual guidance, but the Apostles and their successors are granted a unique teaching charism. Luke 10:16 establishes a specific ecclesiastical authority beyond individual spiritual experience. The argument falsely equates these spiritual promises with blanket infallibility, which isn't supported by Scripture, tradition, and Catholic doctrine. My opponent's attempt to dilute apostolic authority misses the fundamental theological nuance.


“Christ singles them out for a special teaching role: "Whoever listens to you listens to me," (Luke 10:16). This promise connects directly to their commission to teach "all nations" (Matthew 28:19-20).”

Jesus says this to Judas too, right before he says “one of you will betray me” (John 13:21). Clearly Judas was not infallible. This promise is about cases where the apostles correctly repeat the doctrine Jesus told them, ... Peter even warns of false prophets who “deny the master who brought them” (2 Peter 2), implying that authorities can fall into error. ... [this promise is] made to people who are clearly capable of error. Since bishops can fall into heresy and give false teaching outside of ecumenical councils, why should we assume that they are infallible during [ecunemical] councils?
My opponent conflates infallibility with its mechanism (councils). Judas's personal sin doesn't contradict infallibility, which concerns doctrinal integrity (see R1, Object of Infallibility; R2, Scriptural Basis #1, #2, #3; R2, Historical Evidence, #2; R2, Authority vs. Infallibility #1).

Peter's warning about false prophets reinforces our argument. Christ's promise wasn't a legalistic checklist but a foundational commissioning of the Church's teaching mission. The specific mechanisms of this authority were to be developed under the Holy Spirit's guidance. The context of "proclaiming the good news" emphasizes the continuous mission to transmit divine truth. The promise isn't about the apostles' personal infallibility but divine protection of the core message they were commissioned to spread. My opponent's argument against divine guidance points to human imperfection, but the Catholic understanding of infallibility doesn't claim personal perfection for individual leaders but divine preservation of core teachings when the Church speaks with full authority through the Holy Spirit. Christ's promise transcends the individual failings of Judas or any other apostle.


[Pro's citation] doesn’t actually establish (or even imply) that ecumenical councils are infallible. A council making a good decision at some point ... does not mean that councils can never err. King David made the correct decision to defeat Goliath (1 Samuel 17) ... The Sanhedrin was put together by Moses (Numbers 11) ... yet they were not infallible ... accepting this teaching from the apostles as accurate and permanent contradicts Catholic teaching, as the apostles say “it has seemed good to the Holy Spirit and to us to impose on you no further burden than these essentials.” The Catholic Church imposes additional burdens on its members, such as telling them they must observe the Eucharistic fast.
My opponent's critique fundamentally misunderstands the significance of the Council of Jerusalem in Acts 15. This passage is not merely an isolated example of a good decision, but a paradigmatic moment demonstrating divine guidance in the Church's collective discernment. The statement "it has seemed good to the Holy Spirit and to us" is far more profound than my opponent suggests. This isn't just a casual acknowledgment, but a declarative assertion of divine collaboration in doctrinal decision-making. The explicit invocation of the Holy Spirit's guidance distinguishes this council from mere human deliberation.

The comparison to King David or the Sanhedrin is misplaced. See R2, Authority vs. Infallibility, #1. Furthermore, the argument about "no further burden" mischaracterizes the council's intent. This specific directive was about Gentile conversion requirements, not a comprehensive limitation on all future Church teachings. The Church's subsequent developments are not contradictions but natural expansions of the apostolic mission, guided by the same Spirit invoked in Acts 15. The very language — "it has seemed good to the Holy Spirit and to us" — is a much more profound theological truth. Acts 15 is a foundational demonstration of the divine guidance promised by Christ to His Church.


Peter swore that he had never met Jesus (Matthew 26), …Peter’s error in Galatians comes very close to erroneous teaching ... Peter either explicitly or implicitly communicated wrong behavior to the others. Pro cedes this as a mistake on Peter’s part but states that “personal sin does not negate doctrinal infallibility.” ... Pro and the Catholic Church want us to read these verses and assume that bishops are infallible during ecumenical councils specifically, when none of the verses is implying infallibility or attributing special authority to councils.
My opponent conflates personal moral failings with doctrinal teaching. There's a fundamental difference between Peter's personal sins and the Church's formal doctrinal pronouncements. In this example, Peter was not making an official doctrinal pronouncement. The Catholic claim to infallibility is not a claim that individual leaders are perfect, but that the Holy Spirit preserves the Church from definitively teaching error on matters of faith and morals when speaking with its full authority. My opponent's argument essentially attempts to destroy the entire concept of divine guidance by pointing to human imperfection. This undermines the understanding that the Spirit of Truth ensures the promulgation of true doctrine through its divine guidance and effective presence. Personal sin does not negate the infallibility ensured under the guidance of the Spirit of Truth (See R1, Object of Infallibility ; R2 Counter-Arguments, Scriptural Basis #1, #2, #3 ; R2 Counter-Arguments, Historical Evidence, #2 ; R2, Authority vs. Infallibility #1)


For scripture to support Catholic claims to infallibility, it would have to say that authorities are perfectly guarded from error specifically when the pope speaks ex cathedra, during ecumenical councils, and in cases when all bishops around the world agree on a teaching. Scripture doesn’t say that
The debate is about whether the Church has a claim to infallibility at all (the principle of infallibility), not about the mechanisms by which that infallibility is expressed (ex cathedra, ecumenical councils, and when all bishops around the world agree on a teaching). The claim that scripture must explicitly outline modern canonical procedures misunderstands how divine revelation and theological understanding develop. Christ's promises were not intended to be a legalistic, procedural manual, but a foundation from which the Church's authority would teach. The development of specific mechanisms for preserving doctrinal truth is a natural progression of the apostolic mission, guided by the Holy Spirit. The argument that these channels are a "later Catholic invention" fundamentally misunderstands how theological understanding grows. The Church's understanding of its own authority is itself a process of divine revelation, not a fabrication. My opponent's argument essentially demands that divine guidance be confined to the exact language and understanding of the first century, ignoring the promise of continued guidance "until the end of the age" (Matthew 28:20). This fundamentally constrains the dynamic, living nature of divine revelation as promised by Christ.


Paul calls the church the “pillar of truth” ... This does not mean the church can never err. The library is a “bulwark of truth” even if some library books contain incorrect information ... Paul’s analogy here is a general metaphor about the church receiving Jesus’ message, not a guarantee of infallibility. Jesus promises to guide the church toward truth with the Holy Spirit and the gospel, but this does not mean that fallible humans will never err or make mistakes
While humans remain fallible, Christ's promise of doctrinal guidance to the Church ensures it is divinely protected from teaching error on matters of faith and morals. In John 16:13, the Greek verb ὁδηγέω (hodēgeō), meaning "to lead or guide," conveys purposeful, active direction by the Holy Spirit, not a mere suggestion. Similarly, Paul's description of the Church as the "pillar and bulwark of truth" (1 Timothy 3:15) is not a passive metaphor but a declaration of its unique, Spirit-guided role in preserving divine revelation. Comparing the Church to a library misinterprets this reality; a library passively stores information, some of which may be false, whereas the Church, as a living organism, is actively guided by the Holy Spirit to safeguard core theological truths. Just as a navigator ensures a ship stays on course despite individual crew errors, the Holy Spirit guarantees the Church's doctrinal integrity, fulfilling Christ's promise that it will be led into all truth.


Historical Evidence for Infallibility.

Pro includes citations from the Church Fathers as evidence for infallibility. Before investigating these citations, we should note that the Church Fathers themselves were not infallible. Origen, for example, had a number of beliefs that are widely considered erroneous today, even by the Catholic Church.
The dismissal of Church Fathers through individual errors misinterprets theological reasoning. Patristic sources are not claimed as personal infallibility, but as collective witnesses to apostolic tradition. Individual theological missteps don't negate the broader consensus on Church authority. The critique reveals a shallow understanding of historical theological methodology. Church Fathers represent a stream of theological reflection, not isolated opinions. Their collective testimony matters more than any single writer's imperfections. The critique of Origen's errors is a red herring. No serious theological argument rests on the absolute perfection of any single Church Father. Attempting to discredit the Church Fathers through individual flaws commits the genetic fallacy — dismissing an entire body of evidence based on problematic components. This is intellectually dishonest and fails to engage with the substantive theological argument.


The “certain truth” refers to the Holy Spirit itself, not what is taught by someone with the Holy Spirit. ... [Pro] claims that “the Spirit guarantees that the Church's definitive teachings on faith and morals ... are preserved from error.” Iraneus’ writing does not support that claim
Irenaeus' language strongly affirms the Church's divinely guaranteed teaching authority. The phrase "certain charisma of truth" is a theological assertion of Spirit-guided doctrinal preservation, underscoring the Holy Spirit's active role in ensuring the Church's teachings remain free from fundamental error. When Irenaeus declares, "where the Church is, there is the Spirit of God," he highlights the Church as a truth-bearing institution, not merely by human effort but through divine guidance. Christ's promise in John 16:13 — to guide the Church "into all truth" — is not confined to the Spirit's mere presence but extends to its active work in ensuring the Church's teachings on faith and morals are preserved from error. Apostolic succession serves as the Spirit-ordained channel for transmitting and safeguarding theological truth. This "certain" truth reflects a living, pneumatological reality where divine guidance operates through the Church's structures, fulfilling Christ's promise and preserving doctrinal integrity across generations.


Tertullian says that it is very unlikely for all churches to err in the same way, not impossible ... If he’s appealing to probability here and not a guarantee of infallibility, that’s already contrary to the Catholic teaching on ecumenical councils. ... Even during the Council of Nicea, different churches were saying different things, and some of them were wrong.
My opponent's reference to disagreements at Nicaea misunderstands infallibility, which applies to the Church's authoritative declarations, not the pre-council disputes they resolve. Similarly, the claim that Tertullian's argument doesn't guarantee the modern Church's infallibility ignores the Church's continuity as the same Spirit-guided body throughout history. Tertullian's argument that "it would be impossible for all churches to err" reflects his confidence in the Holy Spirit as the Church's divine teacher of truth, not a mere appeal to probability. His rhetorical question — "Is it likely...?" — emphasizes the improbability of collective error under the Spirit's guidance, aligning with Catholic teaching on infallibility.


Since one of [the Apostles'] successors isn’t comfortable issuing commands (a show of authority), this is a good reason we shouldn’t assume all church leaders to have the same amount of authority as the apostles.
Ignatius is clear in his letters to the Smyrnaeans and Magnesians, about the primacy and divinely ordained authority of bishops. He viewed bishops as inheritors of the apostles' authority, endowed with the power to govern, teach, and sanctify the faithful. It is a logical leap to argue that Ignatius' reluctance to "issue commandments" undermines the principle of apostolic succession. The humility of Ignatius' tone should be seen as a reflection of his personal reverence for the foundational role of the apostles, not as a denial of the theological continuity between their authority and that of their successors.


We could also say that Israel is from God, or that Adam and Eve are from God, or that the Sanhedrin is from God. Yet Israel, Adam, Eve, and the Sanhedrin all fell into error at various points, as did some of the apostles. Saul and David were God’s anointed kings, but they each abused their authority many times. Despite Christ guiding the apostles into truth, not everything said by the apostles was true.
My opponent's argument conflates the divine origin of authority with the fallibility of individuals exercising it, failing to grasp the Catholic doctrine of infallibility as it pertains to the teaching authority of the Church. The examples cited do not undermine the Catholic understanding of infallibility, as none of these entities were divinely guaranteed infallibility in the specific sense the Church claims.


Thomas Aquinas was writing in the 1200s, a millennium after the early church and well after the Catholic/Orthodox split in 1054. ... Aquinas’ writings don’t tell us what the early church believed. And even if we accepted this writing, the “church universal” has not accepted Catholic infallibility
The opponent's argument commits logical fallacies: chronological snobbery, genetic fallacy, and false equivalence. Aquinas's theological articulation synthesizes centuries of ecclesiastical reflection, not personal innovation. Historical divergences don't invalidate theological principles. Just as scientific consensus emerges through debate, theological truth refines through dialogue. Aquinas provides a philosophical framework for understanding divine guidance through ecclesiastical structures. The real question is whether a coherent theological mechanism exists for preserving divine revelation, which Aquinas eloquently articulates.


Lutheran bishops and Orthodox bishops can both claim unbroken sacramental succession. The third requirement (“continuity of doctrine”) makes infallibility circular. ... in order for successors to be infallible (i.e. correct), they have to teach the same doctrine taught to the apostles (i.e. correct doctrine). In order for a council to be infallible, the authorities at the council can’t be heretics.  Pro simply claims that “the church is infallible.” But which church, and what singles that church out from the others
Apostolic succession encompasses not only valid ordination but also fidelity to the apostolic faith and communion with the successor of Peter, the pope. This is where the Catholic Church distinguishes itself from other Christian traditions. Lutheran bishops lack valid sacramental succession because they departed from essential aspects of sacramental theology, such as the nature of holy orders and the Eucharist, during the Reformation. Orthodox bishops maintain valid sacramental succession but lack full communion with the pope, which the Catholic Church considers essential to the unity of the Church established by Christ. My opponent asks, "Which church, and what singles that church out from the others?" The answer is that the Catholic Church is uniquely identifiable because it is the only church that maintains unbroken sacramental succession, continuity of doctrine, and communion with the successor of Peter.

The claim that the requirement of "continuity of doctrine" makes infallibility circular misunderstands the Catholic teaching on infallibility. Infallibility is grounded in the promise of Christ to the apostles that the Holy Spirit would guide the Church into all truth (John 16:13) and that the gates of hell would not prevail against it (Matthew 16:18). This guarantee ensures that the Church will not formally teach error in matters of faith and morals.


CONCLUSION.

In sum, the Catholic Church's claim to infallibility stands on a foundation of Christ's promises, the Holy Spirit's guidance, and an apostolic succession that has preserved the integrity of the faith from the Christian community to the modern era. Far from being an arbitrary human invention, this principle is rooted in Scripture's assurances that the Church is the "pillar and bulwark of truth," and evidenced historically by the witness of the Church Fathers, the early councils guided by the Spirit, and the Church's teaching through centuries of doctrinal challenges. While individual members have erred and failings abound, the Church's capacity to remain doctrinally sound in defining matters of faith and morals testifies to a divine safeguard promised by Christ. Such infallibility is not a denial of human weakness, but a charism ensuring that amid confusion, moral disputes, and theological upheavals, the Church can present the faithful with the true Gospel of Christ. Ultimately, infallibility is an indispensable gift, enabling believers to trust that Christ's teaching authority endures, that the Holy Spirit's guidance is not a hollow pledge, and that the Church entrusted to the Apostles continues to illuminate the path of salvation until the end of the age.

Con
#6
Thanks to CatholicApologetics for a thought-provoking response!

Framework:
Pro agrees that the Catholic Church claims to be infallible when the pope speaks ex cathedra, during ecumenical councils (universal councils with representatives from Churches everywhere), or if all Catholic bishops around the world agree on a teaching. Claiming to be infallible on matters of faith and morals made through these channels is itself a Catholic doctrine on faith and morals, since it directly tells Catholics which statements to believe. That puts Catholic claims about these channels within the scope of this debate.

Pro states that Catholic “teachings on faith and morals…through established channels…are preserved from error.” The established channels I listed are the goal posts, the point of contention between Pro and me.

“this debate focuses on the broader claim: whether the Catholic Church…possesses protection from error…The mechanisms of infallibility are secondary.”
If the Catholic Church clearly says “under x circumstances, y statements about faith and morals are guaranteed to be correct,” and those statements aren’t guaranteed to be correct, then the Catholic Church isn’t infallible on these matters, because they just gave an incorrect binding doctrine about faith and morals. The Orthodox church disagrees on what x and y are, so they don’t consider the Catholic Church to be infallible. Other churches deny that x and y can be applied to any human authority or group. If the Catholic Church is wrong about the mechanisms, the principle of Catholic infallibility is wrong.

“My opponent initially rejected narrowing down to specific mechanisms (papal infallibility)”
I stated that “Catholics don't believe the pope is infallible all the time, just in some cases.” And I recommended against narrowing the scope of the debate to just the pope, not against looking at the specific claims the Catholic Church makes about infallibility. I’ve also been discussing other channels like ecumenical councils, not just the pope. We can’t say claims and decisions are infallible without even knowing what those claims mean, and a broader scope means Pro needs to justify why we should believe all the designated Catholic channels are infallible.

“My opponent's argument assumes that all claims to authority are equally unsubstantiated without evidence…Catholic Church's unique claims and evidence for infallibility…this debate requires careful evaluation of evidence”
Pro is arguing here that Catholic claims to infallibility are supported by evidence. But my point was that if there isn’t strong evidence for infallibility, the odds are against any individual contradictory claim—in a case where Pro’s evidence isn’t very convincing, the odds are against the Catholic Church (one of many denominations) being right and the other churches all being wrong. If the evidence does come down to a guess, the odds are against Pro, and my burden has been upheld better than theirs.

Burdens
As I said in R1 and R2, to win, my opponent must show beyond a reasonable doubt that we should each of the metrics of Catholic infallibility, showing enough certainty to outweigh all the competing claims and the evidence that church authorities aren’t infallible even as a collective. If we have a reasonable doubt that the Catholic Church is 100% correct on all their claims about faith and morals, they aren’t guaranteed not to err and are fallible. For me to win, I can either show that there are good reasons to believe the Catholic Church isn’t infallible on matters of faith and morals, or that there aren’t strong reasons to believe that it is. (Though I will show that I’ve done both.)


Scripture Doesn’t Support Infallibility:
Pro references sections in earlier rounds where they made arguments…I responded to those already, so I’ll just respond to the new things Pro says.

As the Catholic Church acknowledges, conditional infallibility boils down to, “under x circumstances, it is impossible for y to be wrong.” A scriptural passage saying that the church is sometimes infallible would say what x and y are (and if the Catholic Church is right about x and y, it would say something about ecumenical councils and the pope.) Otherwise, the passage is just vaguely saying that the church often produces truth but not giving us conditions to accept any one command as infallible.

“My opponent conflates general spiritual guidance with institutional infallibility…Luke 10:16 establishes a specific ecclesiastical authority beyond individual spiritual experience…My opponent conflates infallibility with its mechanism (councils)”
On the contrary, Pro’s argument is the one that conflates general spiritual guidance with institutional infallibility, since they have cited verses about the Spirit of Truth (“This is the Spirit of truth, ... he abides with you”) to argue for infallibility. But I agree with Pro that general guidance from the Holy Spirit doesn’t equal infallibility; that supports my argument.

Pro’s argument is also the one inappropriately conflating this verse with councils…it says nothing at all about church councils. “Whoever listens to you listens to me” is talking about spreading the message to nonbelievers or new students, not talking to other authorities at church councils. Pro acknowledges that the verse isn’t talking about the council specifically but about when the apostles are teaching, and Pro agrees that it’s not implying that the apostles are infallible whenever they teach. Yet at the same time, Pro argues this passage implies infallibility during church councils, something it doesn’t even mention. We agree that church authorities can teach both true and false doctrine, but this passage says nothing about what makes doctrine infallible.

“divine preservation of core teachings when the Church speaks”
The Catholic Church is adding new teachings it claims are infallible every time something is declared infallible at a church council. If they only wanted to preserve teachings, they wouldn’t keep holding councils. This verse is talking about cases where the apostles speak the truth, it isn’t saying that every true fact will be preserved, and even Pro and the Catholic Church agree church authorities can still teach heresy.

“My opponent…misunderstands the Council of Jerusalem in Acts 15. This passage is…a paradigmatic moment demonstrating divine guidance in the Church's collective discernment…"it has seemed good to the Holy Spirit and to us" — is a much more profound theological truth.”
Pro agrees that individuals receiving guidance from God and the Holy Spirit does not make them infallible. If guidance does not equal infallibility, then an occasion of apostles together receiving guidance from God does not allow us to conclude that ecumenical councils are guaranteed to be infallible. As I said in R1 and supported in R2, “If the authority given to church leaders here isn’t sufficient for infallibility in 99% of day-to-day operations (something even the Catholic church acknowledges), then we don’t have a basis for assuming that it is sufficient for infallibility at ecumenical councils.”

Furthermore, this is the only passage from Pro from scripture or the early church that mentions a council, the “Council of Jerusalem.” But why would statements about a regional council local to Jerusalem (hence the name) be evidence of ecumenical councils specifically being infallible, more so than local councils? As I’ve stated in each round, Catholics accept ecumenical councils as infallible, not all councils. Why would Luke even be thinking of ecumenical councils when writing this? The Council of Nicea, the first ecumenical council and the one I referenced in R2, happened centuries after the earliest church writing, after the scripture and early church fathers Pro is citing. Pro’s only response to my point about Nicea is to argue that Tertullian supported Catholic infallibility, even though Tertullian died before Nicea (the first ecumenical council) was held. We’d need evidence specifically about ecumenical councils (those where authorities from all regions are invited) to support the Catholic claim that ecumenical councils in particular are infallible.

“the argument about "no further burden"...was about Gentile conversion requirements, not a comprehensive limitation on all future Church teachings.”
But then this runs contrary to Pro’s case—it implies this council is just giving guidelines for the present moment, not making permanent statements about faith and morals as the Catholic Church claims it can at ecumenical councils today.

“Peter was not making an official doctrinal pronouncement. The Catholic claim to infallibility is…that the Holy Spirit preserves the Church from definitively teaching error on matters of faith and morals when speaking with its full authority…The debate is about whether the Church has a claim to infallibility at all…not about the mechanisms by which that infallibility is expressed...the promise of continued guidance "until the end of the age" (Matthew 28:20)”
The point is that the passages don’t make authorities infallible in general, which Pro agrees with. Pro’s case relies on a distinction between the Catholic teaching on infallibility at ecumenical councils and authority in general, yet this distinction does not appear in the verses they cite. Pro even agrees that Jesus giving authority to the apostles isn’t giving a specific context in which the church is infallible and isn’t referencing councils. If this passage doesn’t say that the church is infallible in any particular case, either during ecumenical councils, or when a certain person teaches, then we’re left without any promise that the church won’t err at any of these times. Pro agrees the church can err, and as far as we know from these verses, it could be at any point.

Even though Pro states, “the Spirit of Truth ensures the promulgation of true doctrine,” the verses they cite are being addressed to people who aren’t infallible and often make mistakes—since the verses don’t point out any particular mechanism like ecumenical councils as infallible, we’re still left with the possibility of error in any of those circumstances. If the church can still err in any circumstance, it cannot be said to be infallible in any sense; there’s never a time when these verses guarantee that authorities will not err.

Hence, the case for infallibility relies entirely on later claims of infallibility during specific circumstances. Again, by the time that the Catholic Church formalized its infallibility at the First Vatican Council in 1868, there were plenty of groups (Protestants, Orthodox, etc.) that felt the influence of the Holy Spirit was calling them to reject Catholic teachings.

“Continued guidance” doesn’t mean we should accept any claim by some person or group with the Holy Spirit, especially claims of infallibility (since we repeatedly see authorities like the apostles and groups of authorities like the Sanhedrin being fallible). There are many churches and sects with contradictory claims which they claim to be God’s guidance. Following Pro’s logic to its natural conclusion, we’d have to accept all those contradictory claims as part of God’s “guidance until the end of the age.”

“In John 16:13 [“the Spirit of truth…will guide you into all truth”]...conveys active direction by the Holy Spirit…Paul's description of the Church as the "pillar and bulwark of truth" (1 Timothy 3:15)...a declaration of its unique, Spirit-guided role in preserving divine revelation…Comparing the Church to a library misinterprets this…a library passively stores information, some of which may be false, whereas the Church, as a living organism, is actively guided by the Holy Spirit to safeguard core theological truths.”
The point of the library comparison is that an institution can be called a “bulwark of truth” if it contains important true information, but this doesn’t mean all of the information it provides under some specific circumstance is guaranteed to be true. Extend my point from R2 that God promised Israel would be “a kingdom of priests and a holy nation,” and that God guided the Israelites into truth (actively and purposefully), yet this didn’t mean that Israel’s authorities (even as a group) acted in a holy way all the time. They often strayed from the truth.

“promise of Christ that the…gates of hell would not prevail against [the Church]”
Many churches have many active followers, so the gates of hell have not prevailed. This promise says nothing about councils or the pope, and it makes no guarantees about authorities being free from error in any context.


Historical Evidence Doesn’t Support Infallibility:
“The dismissal of Church Fathers…Individual theological missteps don't negate the broader consensus on Church authority.”
I didn’t dismiss the church fathers completely—I said they give some insight into the church at their time period. But a single opinion, or two loosely related opinions, aren’t a consensus—we would need multiple church fathers clearly observing the same widespread belief in infallibility under the circumstances the Catholic Church suggests. Otherwise, it’s just an opinion, not evidence of widespread consensus in the early church. That said, I see no evidence that any of the church fathers Pro cites believe in infallibility at all.

“The phrase "certain charisma of truth"...underscoring the Holy Spirit's active role in ensuring the Church's teachings remain free from fundamental error.”
Receiving certain truth is not a guarantee that one cannot fall into error. Even apostles strayed from the truth at times. The claim that councils of church authorities cannot stray from the truth on faith and morals in certain contexts is unsubstantiated here; it’s a level of specificity that even Pro agrees isn’t given early on. Again, extend my point from R2 that Israel was guided into the truth yet still fell into error, as did many authorities and groups of authorities.

“My opponent's reference to disagreements at Nicaea misunderstands infallibility, which applies to the Church's authoritative declarations, not the pre-council disputes they resolve…Tertullian's argument that "it would be impossible for all churches to err"”
Tertullian's confidence is that at least one or more churches will probably be guided into truth. (He doesn’t say “impossible,” he says “likely”). But nothing is being said here about ecumenical councils or that singles out modern Catholic doctrine from the doctrine of any other church. Again, saying it’s unlikely for all churches to be wrong doesn’t make any ecumenical council infallible (much less all of them), since Pro acknowledges there were dissenting groups even before and during Nicea. Even some bishops at the council rejected the outcome, and the others signed it under threat from the emperor. The channels that the Catholic Church claims are infallible aren’t even mentioned in Tertullian's text.

“Ignatius is clear in his letters…about the primacy and divinely ordained authority of bishops…It is a logical leap to argue that Ignatius' reluctance to "issue commandments" undermines the principle of apostolic succession.”
Even if the bishop follows the role of the apostle in some cases such as the day to day church activities acknowledged in this letter, we cannot conclude on the basis of title alone that a bishop is as authoritative in all cases as the apostles. Ignatius himself wasn’t comfortable issuing commands as the apostles did. This is not a justification for saying that bishops have the same level of authority as the apostles in all cases, much less when discussing matters of faith and morals. Even if they did, I’ve established that authority does not imply infallibility in any context.

“‘We could also say that Israel is from God, or that Adam and Eve are from God, or that the Sanhedrin is from God.’...My opponent's argument conflates the divine origin of authority with the fallibility of individuals exercising it.”
My response was addressing the passage that stated “the apostles are from Christ.” The point is that some group being from God does not make them infallible…Pro is the one conflating these things and implying that being from Christ implies infallibility in some context.

“Aquinas's theological articulation synthesizes centuries of ecclesiastical reflection…Historical divergences don't invalidate theological principles…The real question is whether a coherent theological mechanism exists for preserving divine revelation”
The point was that Aquinas’ opinion was one among many conflicting opinions at the time, after the Great Schism when the Orthodox church rejected Catholicism, and it was given over a millennia after the early church. This does not indicate a consensus among the apostles or the early church, any more than a writing by Luther indicates a consensus. And again, even if we accepted this writing, the “church universal” has not accepted Catholic infallibility—Orthodox and Protestant churches disagree with it, not to mention Christians who were punished in Catholic or Orthodox churches for disagreeing with authorities.


Authority ≠ Infallibility:
Pro extends their earlier arguments against my comparison to other authorities; I extend the bulk of my responses. I’ll reiterate though that despite acting as a group with their full authority, the Sanhedrin still erred when accusing Jesus of blasphemy (Matthew 26). So authorities acting as a group is not a guarantee that they are free from error.


Church Authorities Contradict:
“While the Orthodox Church shares apostolic succession, it lacks universal unity due to the absence of a central teaching authority.”
First, this is false: the Ecumenical Patriarch of Constantinople, though not considered infallible, is a central authority considered the “first among equals” in the Eastern Orthodox Church. Second, this assumes having an individual with central authority makes the Catholic claim to having correct doctrine superior to others like the Lutheran claim, but Pro does not justify this assumption. Authority (not infallibility) was given to all the apostles in general, and Pro does not justify how anything from scripture or the early church points to papal supremacy (the pope as a distinct office meant to be permanently authoritatively above other apostolic successors).

“Protestant denominations reject apostolic succession”
As I linked in R1, some Lutheran churches have maintained apostolic succession.

“relying instead on sola scriptura, a doctrine lacking biblical support”
Pro doesn’t justify their claim that sola scriptura violates the bible. Sola Scriptura does not mean you can’t have opinions that aren’t specified in scripture, it means Lutherans reject Catholic authorities’ claims of infallibility.

“Orthodox bishops maintain valid sacramental succession but lack full communion with the pope, which the Catholic Church considers essential to the unity of the Church”
Saying Catholic practices make them legitimate because they follow Catholic doctrine is as circular as saying that Orthodox practices make them legitimate because they follow Orthodox doctrine. Again, Pro doesn’t make an argument for papal supremacy, they just assume it’s true when other Christian groups reject it.

“Apostolic succession encompasses not only valid ordination but also fidelity to the apostolic faith…uniquely identifiable because it is the only church that maintains unbroken sacramental succession, continuity of doctrine”
As I said, other churches have unbroken succession. Pro doesn’t justify why Catholics are the ones with “fidelity to the apostolic faith” and not the Orthodox church, or other denominations that reject council infallibility altogether.


Conclusion:
Writings from scripture and the early church give no guarantee of freedom from error (infallibility) in any church. Later Catholic claims to infallibility contradict claims made by many other denominations and the continuous precedent of human authorities being fallible.