As a rule we disbelieve all the facts and theories for which we have no use.

'Pure experience' is the name I gave to the immediate flux of life which furnishes the material to our later reflection with its conceptual categories.

Tell him to live by yes and no -- yes to everything good, no to everything bad.

If evolution and the survival of the fittest be true at all, the destruction of prey and of human rivals must have been among the most important. . . . It is just because human bloodthirstiness is such a primitive part of us that it is so hard to eradicate, especially when a fight or a hunt is promised as part of the fun.

Algebra is a form of low cunning.

Act as if what you do makes a difference. It does.