Science can only ascertain what is, but not what should be, and outside of its domain value judgements of all kinds remain necessary.

One cannot learn so well as by experiencing it oneself.

When a man, after long years of searching, chances upon a thought which discloses something of the beauty of this mysterious universe, he should not therefore be personally celebrated. He is already sufficiently paid by his experience of seeking and finding.

I have never looked upon ease and happiness as ends in themselves - this critical basis I call the ideal of a pigsty. The ideals that have lighted my way, and time after time have given me new courage to face life cheerfully, have been Kindness, Beauty, and Truth. Without the sense of kinship with men of like mind, without the occupation with the objective world, the eternally unattainable in the field of art and scientific endeavors, life would have seemed empty to me. The trite objects of human efforts - possessions, outward success, luxury - have always seemed to me contemptible.

The flag is a symbol of the fact that man is still a herd animal.

The health of society thus depends quite as much on the independence of the individuals composing it as on their close political cohesion.

Thus I came...to a deep religiosity, which, however, reached an abrupt end at the age of 12. Through the reading of popular scientific books I soon reached a conviction that much in the stories of the Bible could not be true....Suspicion against every kind of authority grew out of this experience...an attitude which has never left me.