Mathematical proofs, like diamonds, are hard as well as clear.

The tactician knows what to do when there is something to do; whereas the strategian knows what to do when there is nothing to do.

A project without some nonsense is not a real project.

De helft van de patiënten sterft thuis na euthanasie. Als je een goed karakter hebt, dan denk je dat het is omdat de mensen graag thuis sterven. Heb je een slecht karakter, dan denk je dat het is omdat ziekenhuizen gewoon zeggen: wil je euthanasie, regel dat dan thuis.

I do not think there is any other mental strain comparable to the exertion to which a tournament game subjects the chess master. Working at what seemed to me the most difficult mathematical problems has never exhausted me nearly as much as playing in a chess tournament; and of all intellectual applications mathematical work is surely the hardest. That is why physical fitness is a most important factor in tournament chess and why young players, whose brains can stand the poisons of fatigue much longer than those of older players have a great advantage.