There are two kinds of disease of the soul, vice and ignorance.

I know one thing, that I know nothing.

By far the greatest and most admirable form of wisdom is that needed to plan and beautify cities and human communities.

There is but one evil, ignorance.

The life of which meaning one never ponders is not worth living

No one can teach, if by teaching we mean the transmission of knowledge, in any mechanical fashion, from one person to another. The most that can be done is that one person who is more knowledgeable than another can, by asking a series of questions, stimulate the other to think, and so cause him to learn for himself.

If you can do only a little. Do what you can. What you cannot enforce, do not command.