I have found, for example, that if I have to write upon sum rather difficult topic, the best plan is to think about it with very great intensity-the greatest intensity of which I am capable-for a few hours or days, and at the end of that time give orders, so to speak (to my subconscious mind) that the work is to proceed underground. After some months I return consciously to the topic and find that the work has been done.

In the first place a philosophical proposition must be general. It must not deal specially with things on the surface of the earth, or within the solar system, or with any other portion of space and time. . . . This brings us to a second characteristic of philosophical propositions, namely that they must be a priori. A philosophical proposition must be such as can neither be proved nor disproved by empirical evidence. . . . Philosophy, if what has been said is correct, becomes indistinguishable from logic as that word has now come to be used.

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.

Science may set limits to knowledge, but should not set limits to imagination.

Can a society in which thought and technique are scientific persist for a long period, as, for example, ancient Egypt persisted, or does it necessarily contain within itself forces which must bring either decay or explosion?

Indemnity for the past and security for the future.

At all times, except when a monarch could enforce his will, war has been facilitated by the fact that vigorous males, confident of victory, enjoyed it, while their females admired them for their prowess.