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.

Official morality has always been oppressive and negative: it has said "thou shalt not," and has not troubled to investigate the effect of activities not forbidden by the code.

But it is just this characteristic of simplicity in the laws of nature hitherto discovered which it would be fallacious to generalize, for it is obvious that simplicity has been a part cause of their discovery, and can, therefore, give no ground for the supposition that other undiscovered laws are equally simple.

The satisfaction to be derived from success in a great constructive enterprise is one of the most massive that life has to offer.

In science the successors stand upon the shoulders of their predecessors; where one man of supreme genius has invented a method, a thousand lesser men can apply it. ... In art nothing worth doing can be done without genius; in science even a very moderate capacity can contribute to a supreme achievement.

The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts.

The man who has fed the chicken every day throughout its life at last wrings its neck instead, showing that more refined views as to the uniformity of nature would have been useful to the chicken.