For all the tribulations in our lives, for all the troubles that remain in the world, the decline of violence is an accomplishment that we can savor - and an impetus to cherish the forces of civilization and enlightenment that made it possible.

M.I.T. has a reputation for turning out Dilberts. They may be brilliant in what they do, but no one can understand what they say.

A word is an arbitrary label - that's the foundation of linguistics. But many people think otherwise. They believe in word magic: that uttering a spell, incantation, curse, or prayer can change the world. Don't snicker: Would you ever say, 'Nothing has gone wrong yet' without looking for wood to knock?

Plants can't very well defend themselves by their behavior, so they resort to chemical warfare, and plants are saturated with toxins and irritants to deter creatures like us who want to eat them.

The indispensability of reason does not imply that individual people are always rational or are unswayed by passion and illusion. It only means that people are capable of reason, and that a community of people who choose to perfect this faculty and to exercise it openly and fairly can collectively reason their way to sounder conclusions in the long run. As Lincoln observed, you can fool all of the people some of the time, and you can fool some of the people all of the time, but you can't fool all of the people all of the time.

Just as blueprints don't necessarily specify blue buildings, selfish genes don't necessarily specify selfish organisms. As we shall see, sometimes the most selfish thing a gene can do is build a selfless brain. Genes are a play within a play, not the interior monologue of the players.

People have long assumed that violence is necessary for political change. Rulers never cede power voluntarily, the argument goes, so progressives have no choice but to contemplate the use of force to bring about a better world, mindful of the trade-off between a small amount of violence now and acceptance of an unjust status quo indefinitely.