When time permits, I try to see interesting people in the cities I visit. In Seattle, I met Paul Allen, the co-founder of Microsoft, who is shy in personality but flamboyant in his philanthropy.

Photography is a kind of virtual reality, and it helps if you can create the illusion of being in an interesting world.

After their return from Babylon, the practice of human sacrifice died out among the Jews, but survived as an ideal in one of its break-away sects, which believed that God accepted the torture-sacrifice of an innocent man in exchange for not visiting a worse fate on the rest of humanity. The sect is called Christianity.

People today sometimes get uncomfortable with empirical claims that seem to clash with their political assumptions, often because they haven't given much thought to the connections.

I think students should know something about religion as a historical phenomenon, in the same way that they should know something about socialism and humanism and the other great ideas that have shaped political philosophies and therefore the course of human events.

Commerce, trade and exchange make other people more valuable alive than dead, and mean that people try to anticipate what the other guy needs and wants. It engages the mechanisms of reciprocal altruism, as the evolutionary biologists call it, as opposed to raw dominance.

I think that metaphor really is a key to explaining thought and language. The human mind comes equipped with an ability to penetrate the cladding of sensory appearance and discern the abstract construction underneath - not always on demand, and not infallibly, but often enough and insightfully enough to shape the human condition. Our powers of analogy allow us to apply ancient neural structures to newfound subject matter, to discover hidden laws and systems in nature, and not least, to amplify the expressive power of language itself.