There is no greater impediment to progress in the sciences than the desire to see it take place too quickly.

Nothing makes one old so quickly as the ever-present thought that one is growing older.

It is almost everywhere the case that soon after it is begotten the greater part of human wisdom is laid to rest in repositories.

Doubt must be no more than vigilance, otherwise it can become dangerous.

If you are going to build something in the air it is always better to build castles than houses of cards.

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.