“The principle of contradiction establishes merely the agreement of concepts, but does not itself produce concepts.”

“...a genuine work of art, can never be false, nor can it be discredited through the lapse of time, for it does not present an opinion but the thing itself.”

“The fourfold root of the principle of sufficent reason is "Anything perceived has a cause. All conclusions have premises. All effects have causes. All actions have motives.”

“Faith is like love: it does not let itself be forced.”

“It is easy to understand that in the dreary middle ages the Aristotelian logic would be very acceptable to the controversial spirit of the schoolmen, which, in the absence of all real knowledge, spent its energy upon mere formulas and words, and that it would be eagerly adopted even in its mutilated Arabian form, and presently established as the centre of all knowledge.”

“If life — the craving for which is the very essence of our being — were possessed of any positive intrinsic value, there would be no such thing as boredom at all: mere existence would satisfy us in itself, and we should want for nothing.”

“Students and scholars of all kinds and of every age aim, as a rule, only at information, not insight. They make it a point of honour to have information about everything, every stone, plant, battle, or experiment and about all books, collectively and individually. It never occurs to them that information is merely a means to insight, but in itself is of little or no value.”