Horses have made civilization possible.

Flying has changed how we imagine our planet, which we have seen whole from space, so that even the farthest nations are ecological neighbors. It has changed our ideas about time. When you can gird the earth at 1,000 m.p.h., how can you endure the tardiness of a plumber? Most of all, flying has changed our sense of our body, the personal space in which we live, now elastic and swift. I could be in Bombay for afternoon tea if I wished. My body isn't limited by its own weaknesses; it can rush through space.

I'm fascinated how often and with what whole-heartedness people will risk their lives to perform acts of courage, sacrifice, and compassion for total strangers.

Couples are jigsaw puzzles that hang together by touching in just enough points. They're never total fits or misfits. In time, a pair invents its own commonwealth, complete with anthems, rituals, and lingos-a cult of two with fallible gods.

One of the keystones of romantic love - and also of the ecstatic religion practiced by mystics - is the powerful desire to become one with the beloved.

There is a furnace in our cells, and when we breathe we pass the world through our bodies, brew it lightly, and turn it loose again, gently altered for having known us.

As people flock to urban centers where ground space is limited, cities with green walls and roofs and skyscraper farms offer improved health and well-being, renewable resources, reliable food supply, and relief to the environment.