Doubt is the beginning of wisdom

Even when laws have been written down, they ought not always to remain unaltered.

Knowledge of the fact differs from knowledge of the reason for the fact.

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.

If some animals are good at hunting and others are suitable for hunting, then the Gods must clearly smile on hunting.

It is the mark of an educated mind to expect that amount of exactness which the nature of the particular subject admits. It is equally unreasonable to accept merely probable conclusions from a mathematician and to demand strict demonstration from an orator.

Those who cannot bravely face danger are the slaves of their attackers.