I certainly know The Truth.
But I don't know how many germs are swimming in my nose.
Because I know The Truth, I know the difference between faith in knowledge of The Truth and The Truth itself.
Since I am surprised, since I learn things, since I don't know how many germs are swimming in my nose, I know that I don't know everything. Since I don't know everything, I don't know God. But I know this from knowing God.
And this is really not an easy thing to communicate, especially to someone who makes knowledge their idol before God.
The Truth =/= Knowledge
Even true knowledge is not the truth. In fact, true knowledge is to know this even.
True knowledge is epignosis.
And how do you communicate this knowledge beyond knowledge?
It is as absurd as communicating the uncreated through the medium of creation.
And that is why we have The Word of God, Jesus Christ here in the flesh, the Trinity of Father, Son, Holy Spirit. The mysteries of this true knowledge is communicated in these doctrines, to those who have a mind to understand.