I have come to know the mutability of all human relationships and have learned to insulate myself against both heat and cold so that a temperature balance is fairly well assured.

Insofar as mathematics is true, it does not describe the real world. Insofar as it describes the real world, it is not true.

Creating a new theory is not like destroying an old barn and erecting a skyscraper in its place. It is rather like climbing a mountain and gaining new and wider views.

As far as I'm concerned, I prefer silent vice to ostentatious virtue.

The world is a dangerous place to live; not because of the people who are evil, but because of the people who don't do anything about it.

Each makes this cosmos and its construction the pivot of his emotional life, in order to find in this way peace and security which he can not find in the narrow whirlpool of personal experience.

But there is another reason for the high repute of mathematics: it is mathematics that offers the exact natural sciences a certain measure of security which, without mathematics, they could not attain.