He who thinks half-heartedly will not believe in God; but he who really thinks has to believe in God.

Yeah, sex is cool, but have you tried solving the brachistochrone problem in a single night?

I do not know what I may appear to the world; but to myself, I seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.

Physics, beware of metaphysics.