"Suppose aliens invade the earth and threaten to obliterate it in a year's time unless human beings can find the Ramsey number for red five and blue five. We could marshal the world's best minds and fastest computers, and within a year we could probably calculate the value. If the aliens demanded the Ramsey number for red six and blue six, however, we would have no choice but to launch a preemptive attack."

"Thousands — millions and billions — of animals are killed for food. That is very sad. We human beings can live without meat, especially in our modern world. We have a great variety of vegetables and o…"

"I cannot, if I am in the field for glory, be kept out of sight. Probably my services may be forgotten by the great, by the time I get Home; but my mind will not forget, nor cease to feel, a degree of …"

"I've probably been working on this for two years. It's a long time to spend on something that means absolutely nothing. But that's what I do; that's what people want me to do, is spend a lot of time w…"

"If people were always kind and obedient to those who are cruel and unjust; the wicked people would have it all their own way: they would never feel afraid, and so they would never alter, but would gro…"