Every great and deep difficulty bears in itself its own solution. It forces us to change our thinking in order to find it.

A physicist visits a colleague and notices a horseshoe hanging on the wall above the entrance. 'Do you really believe that a horseshoe brings luck?' he asks. 'No,' replies the colleague, 'but I've been told that it works even if you don't believe in it.'

A person who wasn't outraged on first hearing about quantum theory didn't understand what had been said.

There is no hope for any speculation that does not look absurd at first glance.

Some things are so serious, they can only be joked about.

It is, indeed, perhaps the greatest prospect of humanistic studies to contribute through an increasing knowledge of the history of cultural development to that gradual removal of prejudices which is the common aim of all science.

The opposite of every great idea is another great idea.