"Anybody who has been seriously engaged in scientific work of any kind realizes that over the entrance to the gates of the temple of science are written the words: 'Ye must have faith.'"

"The highest court is in the end one's own conscience and conviction—that goes for you and for Einstein and every other physicist—and before any science there is first of all belief. For me, it is beli…"

"Science advances funeral by funeral."

"The history of science shows that the human mind is capable of understanding the most complex phenomena."

"The quantum of action, as I called it, was a purely formal assumption and I really did not think much about it."