“For your Bildung you should choose the most difficult and splendid problem, but as subject for a dissertation choose no more than a very limited and remote corner.”

“An artist chooses his subjects.. that is the way he praises.”

“There are terrible people who, instead of solving a problem, bungle it and make it more difficult for all who come after. Whoever can't hit the nail on the head should, please, not hit at all.”

“God is a conjecture; but I desire that your conjectures should be limited by what is thinkable. Can you think a god? [...] You should think through your own senses to their consequences.”

“In some remote corner of the universe, poured out and glittering among innumerable solar systems, there once was a star on which clever animals invented knowledge.”

“But having quills is a waste, even a double luxury when one can choose not to have quills but open hands.”

“Dangerous Helpfulness. There are people who want to make men's lives more difficult for no other reason than afterwards to offer them their prescriptions for making life easier -- their Christianity, for example.”