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.

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

Most of the time I am sunk in thought, but at some point on each walk there comes a moment when I look up and notice, with a kind of first-time astonishment, the amazing complex delicacy of the words, the casual ease with which elemental things come together to form a composition that is—whatever the season, wherever I put my besotted gaze—perfect.

I turned to my own bunk and examined it with a kind of appalled fascination. If the mattress stains were anything to go by, a previous user had not so much suffered from incontinence as rejoiced in it. He had evidently included the pillow in his celebrations.

The remarkable position in which we find ourselves is that we don't actually know what we actually know.

If a potato can produce vitamin C, why can't we? Within the animal kingdom only humans and guinea pigs are unable to synthesize vitamin C in their own bodies. Why us and guinea pigs? No point asking. Nobody knows.

I see litter as part of a long continuum of anti-social behaviour.