It was the experience of mystery - even if mixed with fear - that engendered religion.

Cogito cogito ergo cogito sum (I think that I think, therefore I think that I am.)

If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations – then so much the worse for Maxwell's equations. If it is found to be contradicted by observation – well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.

To a request to explain what an electron is really supposed to be we can only answer, 'It is part of the A B C of physics.'

The most insignificant present has over the most significant past the advantage of reality.

The principles of logic and mathematics are true simply because we never allow them to be anything else.

In the end, it's not the years in your life that count. It's the life in your years.