Personally, people know themselves very poorly.

Without renouncing the support of physics, it is possible for the physiology of the senses, not only to pursue its own course of development, but also to afford to physical science itself powerful assistance.

I can accept the theory of relativity as little as I can accept the existence of atoms.

The fact is, every thinker, every philosopher, the moment he is forced to abandon his one-sided intellectual occupation by practical necessity, immediately returns to the general point of view of mankind.

Strange as it may seem, the power of mathematics rests on its evasion of all
unnecessary thought, and on its wonderful saving of mental operations.

Science always has its origin in the adaptation of thought to some definite field of experience.