Belief systems provide a programme which relieves the necessity of thought.

The rules of logic are to mathematics what those of structure are to architecture.

The moral thing I should wish to say to them is very simple; I should say: "Love is wise - Hatred is foolish." In this world, which is getting more and more closely interconnected, we have to learn to tolerate each other.

The most essential characteristic of scientific technique is that it proceeds from experiment, not from tradition. The experimental habit of mind is a difficult one for most people to maintain; indeed, the science of one generation has already become the tradition of the next

Science, by itself cannot, supply us with an ethic.

The essence of the liberal outlook lies not in what opinions are held, but in how they are held; instead of being held dogmatically, they are held tentatively, and with a consciousness that new evidence may at any moment lead to their abandonment.

The human race may well become extinct before the end of the century. Speaking as a mathematician, I should say the odds are about three to one against survival.