"In the present state of science, it would be a rash thing to assert that any one physical constant is absolutely constant."

"I have looked into most philosophical systems and I have seen that none will work without God."

"The present state of science is such that we cannot hope to explain all the phenomena of nature by means of a few simple laws."

"The human mind is seldom satisfied, and is certainly never exercising its highest functions, when it is doing the work of a calculating machine."

"The first thing that I always do is to try to understand the problem."