"The most dangerous condition for a man or a nation is when his intellectual side is more developed than his spiritual. Is that not exactly the condition of the world today?"

"I consider that a man's brain originally is like a little empty attic, and you have to stock it with such furniture as you choose."

"Healthy scepticism is the basis of all accurate observation."

"The highest and most complex achievement of the human intellect is the power of generalization."

"It is a capital mistake to theorize before one has data."