"“If it be urged that the action of the potato is chemical and mechanical only, and that it is due to the chemical and mechanical effects of light and heat, the answer would seem to lie in an inquiry whether every sensation is not chemical and mechanical in its operation? whether those things which we deem most purely spiritual are anything but disturbances of equilibrium in an infinite series of levers, beginning with those that are too small for microscopic detection, and going up to the human arm and the appliances which it makes use of? whether there be not a molecular action of thought, whence a dynamical theory of the passions shall be deducible? Whether strictly speaking we should not ask what kind of levers a man is made of rather than what is his temperament? How are they balanced? How much of such and such will it take to weigh them down so as to make him do so and so?"

“There is nothing less powerful than knowledge unattached, and incapable of application. That is why what little knowledge I have has done myself personally so much harm. I do not know much, but if I knew a good deal less than that little I should be far more powerful.”

“The pursuit of truth is chimerical. That is why it is so hard to say what truth is. There is no permanent absolute unchangeable truth; what we should pursue is the most convenient arrangement of our ideas.”

“There are two classes, those who want to know and do not care whether others think they know or not, and those who do not much care about knowing but care very greatly about being reputed as knowing.”

“Surely the glory of finally getting rid of and burying a long and troublesome matter should be as great as that of making an important discovery. The trouble is that the coverer is like Samson who perished in the wreck of what he had destroyed; if he gets rid of a thing effectually he gets rid of himself too.”

“Honesty consists not in never stealing but in knowing where to stop in stealing, and how to make good use of what one does steal.”

“He is greatest who is most often in men's good thoughts.”