It is always there, of course, when you come back from the green world. You have been living by sunrise and sunset, by wind and rain, surrounded by the ebb and flow of lives that respond only to such simple, rhythmic elements. But now the tone and tempo of the days switch. Instead of harmony, jangle.

Even in these mercifully emancipated decades, many people still seem quite seriously alarmed at the prospect of sleeping away from officially consecrated campsites, with no more equipment than they can carry on their backs. When pressed, they babble about snakes or bears or even, by God, bandits. But the real barrier, I'm sure, is the unknown.

God is light, we are told, and Hell is outer darkness. But look at a desert mountain stripped bare by the sun, and you learn only geography. Watch darkness claim it, and for a moment you may grasp why God had to create Satan—or man to create both.

Mostly, two miles an hour is good going.

The best dress for walking is nakedness. But our sad though fascinating world rarely offers the right and necessary combinations of weather and privacy, and even when it does the Utopia never seems to last very long.

Under most conditions, the best roof for your bedroom is the sky. This commonsense arrangement saves weight, time, energy, and money.

Every walk of life falls under the Testicular Imperative: Either you have the world by them, or it has you.