We accumulate our opinions at an age when our understanding is at its weakest.

I have often noticed that when people come to understand a mathematical proposition in some other way than that of the ordinary demonstration, they promptly say, "Oh, I see. That's how it must be." This is a sign that they explain it to themselves from within their own system.

First there is a time when we believe everything, then for a little while we believe with discrimination, then we believe nothing whatever, and then we believe everything again - and, moreover, give reasons why we believe.

Prejudices are so to speak the mechanical instincts of men: through their prejudices they do without any effort many things they would find too difficult to think through to the point of resolving to do them.

With prophecies the commentator is often a more important man than the prophet.

He who is enamored of himself will at least have the advantage of being inconvenienced by few rivals.

Everyone is a genius at least once a year.