Plato

No one should be discouraged, Theaetetus, who can make constant progress, even though it be slow.

I do see one large and grievous kind of ignorance, separate from the rest, and as weighty as all the other parts put together. Thinking that one knows a thing when one does not know it. Through this, I believe, all the mistakes of the mind are caused in all of us.

It is difficult to set forth any of the greater ideas, except by the use of examples; for it would seem that each of us knows everything that he knows as if in a dream and then again, when he is as it were awake, knows nothing of it all.

Wonder is the feeling of a philosopher, and philosophy begins in wonder.

No man of sense can put himself and his soul under the control of names... You must consider courageously and thoroughly and not accept anything carelessly.

The attempt to separate everything from everything else is not only not in good taste but also shows that a man is utterly uncultivated and unphilosophical. The complete separation of each thing from all is the utterly final obliteration of all discourse. For our power of discourse is derived from the interweaving of the classes or ideas with one another.

Perception and knowledge could never be the same.

I shall assume that your silence gives consent.

Those who purge the soul believe that the soul can receive no benefit from any teachings offered to it until someone by cross-questioning reduces him who is cross-questioned to an attitude of modesty, by removing the opinions that obstruct the teachings, and thus purges him and makes him think that he knows only what he knows, and no more.

Neither perception nor true opinion, nor reason or explanation combined with true opinion could be knowledge… Then our art of midwifery declare to us that all the offspring that have been born are mere wind-eggs and not worth rearing… and if you remain barren, you will be less harsh and gentler to your associates, for you will have the wisdom not to think you know that which you do not know.