The mind of man is capable of anything—because everything is in it, all the past as well as all the future. What we call imagination is just knowledge of the world.

The mind itself is the medium of all knowledge, and the quality of that knowledge depends upon the quality of the mind. A dull mind will produce dull knowledge; a penetrating mind will penetrate to the heart of things.

Science is a way of thinking much more than it is a body of knowledge. Its goal is not to arrive at immutable truths but to develop progressively better approximations of reality.