William Kingdon Clifford

"I am endeavouring in a general way to explain the laws of double refraction on this hypothesis, but have not yet arrived at any results sufficiently decisive to be communicated."

"We ought not to teach to little children, as a known fact, that which is not a known fact."

"The name philosopher, which meant originally lover of wisdom, has come in some strange way to mean a man who thinks it is his business to explain everything in a certain number of large books. It will be found, I think, that in proportion to his colossal ignorance is the perfection and symmetry of the system which he sets up; because it is so much easier to put an empty room tidy than a full one."

"No mathematician can give any meaning to language about matter, force, inertia, used in text-books of mechanics."

"Remember, then, 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. And for this reason the question what its characters are... is the question of all questions for the human race."

"There is in the true man of science a desire stronger than the wish to have his beliefs upheld; namely, the desire to have them true."