While most of those who hold that the whole heaven is finite say that the earth lies at the center, the philosophers of Italy, the so-called Pythagoreans, assert the contrary. They say that in the middle there is fire, and that the earth is one of the stars, and by its circular motion round the center produces night and day.

The virtues [moral excellence] therefore are engendered in us neither by nature nor yet in violation of nature; nature gives us the capacity to receive them, and this capacity is brought to maturity by habit.

The greatest of all pleasures is the pleasure of learning.

That judges of important causes should hold office for life is a questionable thing, for the mind grows old as well as the body.

So it is clear that the search for what is just is a search for the mean; for the law is the mean.

I will not allow the Athenians to sin twice against philosophy.

The seat of the soul and the control of voluntary movement - in fact, of nervous functions in general, - are to be sought in the heart. The brain is an organ of minor importance.