An atom must be at least as complex as a grand piano.

If a belief is not realized immediately in open deeds, it is stored up for the guidance of the future.

No simplicity of mind, no obscurity of station, can escape the universal duty of questioning all that we believe.

Remember that [scientific thought] is the guide of action; that the truth which it arrives at is not that which we can ideally contemplate without error, but that which we may act upon without fear; and you cannot fail to see that scientific thought is not an accompaniment or condition of human progress, but human progress itself.

He who truly believes that which prompts him to an action has looked upon the action to lust after it, he has committed it already in his heart.

scientific thought does not mean thought about scientific subjects with long names. There are no scientific subjects. The subject of science is the human universe; that is to say, everything that is, or has been, or may be related to man.

Every rustic who delivers in the village alehouse his slow, infrequent sentences, may help to kill or keep alive the fatal superstitions which clog his race.