"Morality is the custom of one's country and the current feeling of one's peers. Cannibalism is moral in a cannibal country."

“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.”