It doesn't behoove elderly persons to follow fashion in their thinking nor in the way they dress.

The greatest thing in this world is not so much where we stand as in what direction we are moving.

I could never have known so well how paltry men are, and how little they care for really high aims, if I had not tested them by my scientific researches. Thus I saw that most men only care for science so far as they get a living by it, and that they worship even error when it affords them a subsistence.

Humans fear reason, but they ought to fear stupidity- for reason can be hard, but stupidity can be fatal.

How can you come to know yourself? Never by thinking, always by doing. Try to do your duty, and you'll know right away what you amount to.

The philosophers must station themselves in the middle.

Alas, I have studied philosophy, the law as well as medicine, and to my sorrow, theology; studied them well with ardent zeal, yet here I am, a wretched fool, no wiser than I was before.