"The true logic of this world is in the calculus of probabilities."

"The only laws of matter are those which our minds must fabricate, and the only laws of mind are fabricated for it by matter."

"Thoroughly conscious ignorance is the prelude to every real advance in science."

"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."