We are boxed in by the boundary conditions of our thinking

When a man is sufficiently motivated, discipline will take care of itself.

[Kepler] had to realize clearly that logical-mathematical theoretizing, no matter how lucid, could not guarantee truth by itself; that the most beautiful logical theory means nothing in natural science without comparison with the exactest experience. Without this philosophic attitude, his work would not have been possible.

Mathematics are well and good but Nature keeps dragging us around by the nose.

I believe that whoever tries to think things through honestly will soon recognize how unworthy and even fatal is the traditional bias against Negroes. What can the man of good will do to combat this deeply rooted prejudice? He must have the courage to set an example by words and deed, and must watch lest his children become influenced by racial bias.

They come into being not through demonstration but through revelation, through the medium of powerful personalities.

If only I had known, I should have become a watchmaker.