Xenophanes speaks thus:—
And no man knows distinctly anything,
And no man ever will.

It is natural that one cannot understand deep and hidden things. Those things that are easily understood are rather shallow.

We cannot understand. The best is perhaps what we understand least.

Facing any part of the observable reality, we are never in possession of complete knowledge, nor in a state of complete ignorance, although usually much closer to the latter state.

We seem never to know what any thing means or is worth until we have lost it.

We suffer only until we realize that we can’t know anything.

This vain presumption, of understanding everything, can have no other basis than never understanding anything. For anyone who had experienced just once the understanding of one single thing, thus truly tasting how knowledge is accomplished, would then recognize that of the infinity of other truths, he understands nothing.

There are no truths, only moments of claryty passing for answers.

Only the shallow know themselves.

Not to understand is profound; to understand is shallow. Not to understand is to be on the inside; to understand is to be on the outside.

We never have any understanding of any subject matter except in terms of our own mental constructs of "things" and "happenings" of that subject matter.

Man, as we realize if we reflect for a moment, never perceives anything fully or comprehends anything completely.

We can be absolutely certain only about things we do not understand.

Human beings never know more than a part, as "through a glass darkly"; and all knowledge comes to us in pieces.