Nature is a tenacious recycler, every dung heap and fallen redwood tree a bustling community of saprophytes wresting life from the dead and discarded, as though intuitively aware that there is nothing new under the sun. Throughout the physical world, from the cosmic to the subatomic, the same refrain resounds. Conservation: it's not just a good idea, it's the law.

evolution is a tinkerer, an ad-hocker, and a jury-rigger. It works with what it has on hand, not with what it has in mind. Some of its inventions prove elegant, while in others you can see the seams and dried glue.

[On women:] We are all yeses. We are worthy enough, we passed inspection, we survived the great fetal oocyte extinctions. In that sense, at least - call it a mechanospiritual sense - we are meant to be. We are good eggs, every one of us.

Astronomers are pure of heart and appealingly puerile. They look into the midnight sky and ask big questions, just as we did when we were in college: Who are we? Where do we come from? And why are we standing around outside on the night before finals, do we want to end up making elevator parts for a living like our father or what?

The surest and most insidious enemy of freedom is not dictatorship, but complacency.

As [The Nation columnist Katha] Pollitt points out, when one starts looking beneath the surface of things and adding together the out-front atheists with the indifferent nonbelievers, you end up with a much larger group of people than Jews, Muslims, Buddhists and Unitarians put together.

Scientists have discovered that the small, brave act of cooperating with another person, of choosing trust over cynicism, generosity over selfishness, makes the brain light up with quiet joy.