Human beings would split the atom and invent television, nylon, and instant coffee before they could figure out the age of their own planet.

Our instinct may be to see the impossibility of tracking everything down as frustrating, dispiriting, perhaps even appalling, but it can just as well be viewed as almost unbearably exciting. We live on a planet that has a more or less infinite capacity to surprise. What reasoning person could possibly want it any other way?

When I was growing up I used to think that the best thing about coming from Des Moines was that it meant you didn't come from anywhere else in Iowa. By Iowa standards, Des Moines is a mecca of cosmopolitanism, a dynamic hub of wealth and education, where people wear three-piece suits and dark socks, often simultaneously.

Take a moment from time to time to remember that you are alive. I know this sounds a trifle obvious, but it is amazing how little time we take to remark upon this singular and gratifying fact. By the most astounding stroke of luck an infinitesimal portion of all the matter in the universe came together to create you and for the tiniest moment in the great span of eternity you have the incomparable privilege to exist.

Britain still has the most reliably beautiful countryside of anywhere in the world. I would hate to be part of the generation that allowed that to be lost.

Black bears rarely attack. But here's the thing. Sometimes they do. All bears are agile, cunning and immensely strong, and they are always hungry. If they want to kill you and eat you, they can, and pretty much whenever they want. That doesn't happen often, but - and here is the absolutely salient point - once would be enough.

If this book has a lesson, it is that we are awfully lucky to be here-and by 'we' I mean every living thing. To attain any kind of life in this universe of ours appears to be quite an achievement. As humans we are doubly lucky, of course: We enjoy not only the privilege of existence but also the singular ability to appreciate it and even, in a multitude of ways, to make it better. It is a talent we have only barely begun to grasp.