Whoever in discussion adduces authority uses not intellect but rather memory.

There are but two powers in the world, the sword and the mind. In the long run the sword is always beaten by the mind.

Many will think they may reasonably blame me by alleging that my proofs are opposed to the authority of certain men held in the highest reverence by their inexperienced judgments; not considering that my works are the issue of pure and simple experience.

Study without desire spoils the memory, and it retains nothing that it takes in.

My works are the issue of simple and plain experience which is the true mistress.

My first day in Chicago, September 4, 1983. I set foot in this city, and just walking down the street, it was like roots, like the motherland. I knew I belonged here.