Nothing happens unless something moves.

The ideals which 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 to the empty. The trite objects of human efforts — possessions, outward success, luxury—have always seemed to me contemptible.

I do not believe in immortality of the individual, and I consider ethics to be an exclusively human concern with no superhuman authority behind it.

Nature shows us only the tail of the lion. But there is no doubt in my mind that the lion belongs with it even if he cannot reveal himself to the eye all at once because of his huge dimension.

It almost seems to me that man was not born to be a carnivore.

The man who regards his own life and that of his fellow-creatures as meaningless is not merely unfortunate but almost disqualified for life.

Each ray of light moves in the coordinate system 'at rest' with the definite, constant velocity V independent of whether this ray of light is emitted by a body at rest or a body in motion.