The hardest thing to understand in the world is the income tax.

It is entirely possible that behind the perception of our senses, worlds are hidden of which we are unaware.

People are like bicycles. They can keep their balance only as long as they keep moving.

The ordinary adult never gives a thought to space-time problems ... I, on the contrary, developed so slowly that I did not begin to wonder about space and time until I was an adult. I then delved more deeply into the problem than any other adult or child would have done.

I have no extraordinary ability. I'm simply an inquisitive individual.

Experts are just trained dogs.

I believe, indeed, that overemphasis on the purely intellectual attitude, often directed solely to the practical and factual, in our education, has led directly to the impairment of ethical values.