Who said “Theories that go counter to the facts of human nature are foredoomed.”?

“In order to shake a hypothesis, it is sometimes not necessary to do anything more than push it as far as it will go.”

“Delight at having understood a very abstract and obscure system leads most people to believe in the truth of what it demonstrates.”

“No theory is good unless it permits, not rest, but the greatest work. No theory is good except on condition that one use it to go on beyond.”

“A young man is a theory, an old man is a fact.”

“It is theory that decides what can be observed.”

“None but a poet can write a tragedy. For tragedy is nothing less than pain transmuted into exaltation by the alchemy of poetry.”

“A people's literature is the great textbook for real knowledge of them. The writings of the day show the quality of the people as no historical reconstruction can.”

“Mind and spirit together make up that which separates us from the rest of the animal world, that which enables a man to know the truth and that which enables him to die for the truth.”

“There are few efforts more conducive to humility than that of the translator trying to communicate an incommunicable beauty. Yet, unless we do try, something unique and never surpassed will cease to exist except in the libraries of a few inquisitive book lovers.”

“When the freedom they wished for most was freedom from responsibility, then Athens ceased to be free and was never free again.”

“The fundamental fact about the Greek was that he had to use his mind. The ancient priests had said, ''Thus far and no farther. We set the limits of thought.'' The Greek said, ''All things are to be examined and called into question. There are no limits set on thought.''”