Free will doesnt exist

"Choice of a person, choice which isnt influenced by any cause"

This definition is agreed upon. The other definitions are to be taken from dictionary of English language, as we do speak English here.

Choice is the act of choosing between two or more possible options.

Thus, person must be able to make a choice which isnt influenced by any cause, in order for free will to exist.

Cause by definition is someone or something making something happen.

In order to not be influenced by any cause, choice must not be caused by anyone or anything.

But the person himself, being the cause of own choice, means choice is influenced by a cause(person), as person who makes the choice fits the definition of a cause.

Thus, free will per agreed definition cannot exist, as choice must be caused by definition, thus cannot be not influenced by a cause, but must be influenced by a cause.

Further, person himself makes choices due to other causes which make a person. If we assume that person makes a choice, then person isnt a choice, thus cannot choose person. Thus, the cause of choice cannot itself be a choice, let alone be not caused by anything or anyone.

The existence of one person alone depends on causes such as environment, choice of other persons to reproduce, level of safety...ect.

The main cause of choice is knowledge. For example, children will usually make worse choices due to less knowledge. With more knowledge, person makes better and different choices, thus we can see that person's choice is influenced by a cause, the knowledge which his environment provides him with.

To put it simply, to be able to choose between options, person must have all knowledge of these options. Thus, choice depends upon a cause(knowledge) and this cause influences a choice. Persons with different levels of knowledge make different choices.

1. A choice must not always have a reason

If we look at the definition of the word "choice", which is "An act of choosing between two or more possibilities" ( Oxford dictionary), The definition does not state a choice always having to have a reason to it. If we for example put down two identical boxes and ask a person to choose one of them, the choice does not have reasoning behind it, and so is only up to the person's free will.  

2. Responding to the first argument

If we go by the definition that free will is "A choice of a person, which is not influenced by any cause" Then we are implying that the choice is only up to the person.  I want to compare the definition to your argument using the earlier example of the boxes. Your argument is discussing the person as a cause, when free will is only interrupted with a cause to change the choices outcome. Not a cause of the person choosing.  In the box scenario, the choice is not influenced by any cause relating to the person. In other words everything that shapes the person up and makes them choose one of the boxes is not influencing the choice, but making the person choose. And if there is nothing influencing the choice It's free will. 

In your other argument you said that the main cause of choice is knowledge. Now i agree with this argument but it does not prove the existence of free will, it proves that most human choices are not the result of free will, but knowledge

By definition of a choice, choice is caused by person. So by that alone, we see that choice has a cause. And person has a cause too, as proved before.

Reasoning isnt the same as cause. Something will just cause person to pick one. If person didnt have a cause here, it would be impossible to even make a choice, and if choices didnt have causes, people would make random choices all the time and nothing in the world would make sense, as people would change mind every second randomly and wouldnt even be able to stick to one choice for longer than a moment.

Now this is a concession.