Man can embody the truth but he cannot know it.

The end of man is knowledge, but there is one thing he can't know.

What a man does not know is greater than he.

The truth exists, but we can never know if it is what we are saying.

A man may imagine things that are false, but he can only understand things that are true.

A man doesn't know what he knows until he knows what he doesn't know.

No human being is constituted to know the truth, the whole truth, and nothing but the truth; and even the best of men must be content with fragments, with partial glimpses, never the full fruition.

As for acquiescing in what a man understands not, or cannot reconcile to his reason, they know best the fruits of it that practice it. For my part, I'm a stranger to it, and cannot reconcile myself to such a principle. On the contrary, I am pretty sure he pretends in vain to convince the judgment, who explains not the nature of the thing. A man may give his verbal assent to he knows not what, out of fear, superstition, indifference, interest, and the like feeble and unfair motives: but as long as he conceives not what he believes, he cannot sincerely acquiesce in it, and remains deprived of all solid satisfaction. ... But he that comprehends a thing, is as sure of it as if he were himself the author.

No man really knows about other human beings. The best he can do is to suppose that they are like himself.

Truth can understand error, but error cannot understand truth.

No man knows fully what has shaped his own thinking

He who thinks he knows, doesn't know. He who knows that he doesn't know, knows.

Socrates: This man, on one hand, believes that he knows something, while not knowing [anything]. On the other hand, I – equally ignorant – do not believe [that I know anything].

A man's dreams are a maze even he cannot know.