"The diversity of phenomena which nature presents to us is so great, and the examples of changes which we are every moment witnessing are so frequent, that it seems to me we cannot too carefully guard against hasty conclusions."
"Doubt is an uncomfortable condition, but certainty is a ridiculous one."
"The greatest mathematicians, like the greatest poets, are men of imagination."
"I believe in God, but I do not believe that God has any of the properties which theologians ascribe to him."
"The true method of knowledge is experiment."