The desire to understand the world and the desire to reform it are the two great engines of progress, without which human society would stand still or retrogress.

We need a science to save us from science.

People are said to believe in God, or to disbelieve in Adam and Eve. But in such cases what is believed or disbelieved is that there is an entity answering a certain description. This, which can be believed or disbelieved is quite different from the actual entity (if any) which does answer the description. Thus the matter of belief is, in all cases, different in kind from the matter of sensation or presentation, and error is in no way analogous to hallucination. A hallucination is a fact, not an error; what is erroneous is a judgment based upon it.

A life which goes excessively against natural impulse is... likely to involve effects of strain that may be quite as bad as indulgence in forbidden impulses would have been. People who live a life which is unnatural beyond a point are likely to be filled with envy, malice and uncharitableness.

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 dictum that human nature cannot be changed is one of those tiresome platitudes that conceal from the ignorant the depths of their own ignorance.

One must expect a war between U.S.A. and U.S.S.R. which will begin with the total destruction of London. I think the war will last 30 years, and leave a world without civilised people, from which everything will have to build afresh - a process taking (say) 500 years.