There is no history of mankind, there are only many histories of all kinds of aspects of human life. And one of these is the history of political power. This is elevated into the history of the world.

We do not know anything - this is the first. Therefore, we should be very modest - this is the second. Not to claim that we do know when we do not - this is the third. That's the kind of attitude I'd like to popularize. There is little hope for success.

It is wrong to think that belief in freedom always leads to victory; we must always be prepared for it to lead to defeat. If we choose freedom, then we must be prepared to perish along with it.

It is not his possession of knowledge, of irrefutable truth, that makes the man of science, but his persistent and recklessly critical quest for truth.

We do not know. We can only guess.

We hate the very idea that our own ideas may be mistaken, so we cling dogmatically to our conjectures.

The game of science is, in principle, without end. He who decides one day that scientific statements do not call for any further test, and that they can be regarded as finally verified, retires from the game.