My mind is my laboratory.

The scientist finds his reward in what Henri Poincare calls the joy of comprehension, and not in the possibility of application to which any discovery may lead.

You are right in speaking of the moral foundations of science, but you cannot turn around and speak of the scientific foundations of morality.

The only justification for our concepts and systems of concepts is that they serve to represent the complex of our experiences; beyond this they have not legitimacy.

The Universe is difficult to comprehend because it is obvious.

The one who walks alone, is likely to find himself in places no one has ever been.

When the nazis came to power, I looked to the universities that prided themselves upon their intellectual freedom, and they failed me. I looked to the German press, which prided itself on the freedom of the press, and it failed me. Until at last the churches stood alone, and that for which I once had little regard earned my respect.