Man…who lives in three places – in the past, in the present, and in the future – can be unhappy if one of these three is worthless. Religion has even added a fourth – eternity.

If nature be regarded as the teacher and we poor human beings as her pupils, the human race presents a very curious picture. We all sit together at a lecture and possess the necessary principles for understanding it, yet we always pay more attention to the chatter of our fellow students than to the lecturer's discourse. Or, if our neighbor copies something down, we sneak it from him, stealing what he himself may have heard imperfectly, and add it to our own errors of spelling and opinion.

It is in the gift for employing all the vicissitudes of life to one's own advantage and to that of one's craft that a large part of genius consists.

Men still have to be governed by deception.

Diogenes, filthily attired, paced across the splendid carpets in Plato's dwelling. Thus, said he, do I trample on the pride of Plato. Yes, Plato replied, but only with another kind of pride.

The worst thing you can possibly do is worrying and thinking about what you could have done.

Be attentive, feel nothing in vain, measure and compare: this is the whole law of philosophy.