Beyond all our actions stands the larger shadow: How are we to choose between what we have been taught to think right and something else which manifestly succeeds?

Knowledge is not a loose leaf notebook of facts.

One original thought is worth the sum total of human knowledge, because it advances the sum total of human knowledge by that one original thought.

The world today is made, it is powered by science; and for any man to abdicate an interest in science is to walk with open eyes towards slavery.

Progress is the exploration of our own error. Evolution is a consolidation of what have always begun as errors. And errors are of two kinds: errors that turn out to be true and errors that turn out to be false (which are most of them). But they both have the same character of being an imaginative speculation. I say all this because I want very much to talk about the human side of discovery and progress, and it seems to me terribly important to say this in an age in which most non-scientists are feeling a kind of loss of nerve.

Every animal leaves traces of what it was; man alone leaves traces of what he created.

The act of imagination is the opening of the system so that it shows new connections. Every act of act of imagination is the discovery of likenesses between two things which were thought unlike. An example is Newton’s thinking of the likeness between the thrown apple and moon sailing majestically in the sky. Hence, the ‘discovery’ of the laws of gravity.