Pure logical thinking cannot yield us any knowledge of the empirical world. All knowledge of reality starts from experience and ends in it.

If a theory can not be explained to a child, then the theory is probably worthless.

My interest in science was always essentially limited to the study of principles.... That I have published so little is due to this same circumstance, as the great need to grasp principles has caused me to spend most of my time on fruitless pursuits.

We must recognize what in our accepted tradition is damaging to our fate and dignity-and shape our lives accordingly.

I have become an obstinate heretic in the eyes of my colleagues. Momentary success carries more power of conviction than reflections upon principles.

Although I have been prevented by outward circumstances from observing a strictly vegetarian diet, I have long been an adherent to the cause in principle. Besides agreeing with the aims of vegetarianism for aesthetic and moral reasons, it is my view that a vegetarian manner of living by its purely physical effect on the human temperament would most beneficially influence the lot of mankind.

I refuse to make money out of my science. My laurel is not for sale like so many bales of cotton.