Max Planck — "The quantum hypothesis will never be overthrown."

"An important scientific innovation rarely makes its way by gradually winning over and converting its opponents: it rarely happens that Saul becomes Paul. What does happen is that its opponents gradual…"

"When you change your opinion, you are not a weakling. You are a scientist."

"The progress of science depends on the freedom of thought."

"The world needs men who can think for themselves, and not just repeat what they have been taught."

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