Ante-Nicene Fathers, Vol I:
JUSTIN MARTYR: Chapter I.—The self-evidencing power...

Chapter I.—The self-evidencing power of truth.

The word of truth is free, and carries its own authority, disdaining to fall under any skilful argument, or to endure the logical scrutiny of its hearers. But it would be believed for its own nobility, and for the confidence due to Him who sends it. Now the word of truth is sent from God; wherefore the freedom claimed by the truth is not arrogant. For being sent with authority, it were not fit that it should be required to produce proof of what is said; since neither is there any proof beyond itself, which is God. For every proof is more powerful and trustworthy than that which it proves; since what is disbelieved, until proof is produced, gets credit when such proof is produced, and is recognised as being what it was stated to be. But nothing is either more powerful or more trustworthy than the truth; so that he who requires proof of this is like one who wishes it demonstrated why the things that appear to the senses do appear. For the test of those things which are received through the reason, is sense; but of sense itself there is no test beyond itself. As then we bring those things which reason hunts after, to sense, and by it judge what kind of things they are, whether the things spoken be true or false, and then sit in judgment no longer, giving full credit to its decision; so also we refer all that is said regarding men and the world to the truth, and by it judge whether it be worthless or no. But the utterances of truth we judge by no separate test, giving full credit to itself. And God, the Father of the universe, who is the perfect intelligence, is the truth. And the Word, being His Son, came to us, having put on flesh, revealing both Himself and the Father, giving to us in Himself resurrection from the dead, and eternal life afterwards. And this is Jesus Christ, our Saviour and Lord. He, therefore, is Himself both the faith and the proof of Himself and of all things. Wherefore those who follow Him, and know Him, having faith in Him as their proof, shall rest in Him. But since the adversary does not cease to resist many, and uses many and divers arts to ensnare them, that he may seduce the faithful from their faith, and that he may prevent the faithless from believing, it seems to me necessary that we also, being armed with the invulnerable doctrines of the faith, do battle against him in behalf of the weak.