“It was the kind of pure, undiffused light that can only come from a really hot blue sky, the kind that makes even a concrete highway painful to behold and turns every distant reflective surface into a little glint of flame. Do you know how sometimes on very fine days the sun will shine with a particular intensity that makes the most mundane objects in the landscape glow with an unusual radiance, so that buildings and structures you normally pass without a glance suddenly become arresting, even beautiful? Well, they seem to have that light in Australia nearly all the time.”

“At the foot of the mountain, the park ended and suddenly all was squalor again. I was once more struck by this strange compartmentalization that goes on in America -- a belief that no commercial activities must be allowed inside the park, but permitting unrestrained development outside, even though the landscape there may be just as outstanding. America has never quite grasped that you can live in a place without making it ugly, that beauty doesn't have to be confined behind fences, as if a national park were a sort of zoo for nature.”

“You may not feel outstandingly robust, but if you are an average-sized adult you will contain within your modest frame no less than 7 X 10^18 joules of potential energy—enough to explode with the force of thirty very large hydrogen bombs, assuming you knew how to liberate it and really wished to make a point. Everything has this kind of energy trapped within it. We're just not very good at getting it out. Even a uranium bomb—the most energetic thing we have produced yet—releases less than 1 percent of the energy it could release if only we were more cunning.”

“I glanced at my watch - it was two minutes to eleven; just right for lunch when and if we ever got to the godforsaken lodge - and took some comfort from the thought that at least I still had my wits about me. Or at least I felt as if I did. Presumably, a confused person would be too addled to recognize that he was confused. Ergo, if you know that you are not confused then you are not confused. Unless, it suddenly occurred to me - and here was an arresting notion - unless persuading yourself that you are not confused is merely a cruel, early symptom of confusion. Or even an advanced symptom. Who could tell? For all I knew I could be stumbling into some kind of helpless preconfusional state characterized by the fear on the part of the sufferer that he may be stumbling into some kind of helpless preconfusional state. That's the trouble with losing your mind; by the time it's gone, it's too late to get it back.”

“Distance changes utterly when you take the world on foot. A mile becomes a long way, two miles literally considerable, ten miles whopping, fifty miles at the very limits of conception. The world, you realize, is enormous in a way that only you and a small community of fellow hikers know. Planetary scale is your little secret.Life takes on a neat simplicity, too. Time ceases to have any meaning. When it is dark, you go to bed, and when it is light again you get up, and everything in between is just in between. It’s quite wonderful, really.You have no engagements, commitments, obligations, or duties; no special ambitions and only the smallest, least complicated of wants; you exist in a tranquil tedium, serenely beyond the reach of exasperation, “far removed from the seats of strife,” as the early explorer and botanist William Bartram put it. All that is required of you is a willingness to trudge.There is no point in hurrying because you are not actually going anywhere. However far or long you plod, you are always in the same place: in the woods. It’s where you were yesterday, where you will be tomorrow. The woods is one boundless singularity. Every bend in the path presents a prospect indistinguishable from every other, every glimpse into the trees the same tangled mass. For all you know, your route could describe a very large, pointless circle. In a way, it would hardly matter.At times, you become almost certain that you slabbed this hillside three days ago, crossed this stream yesterday, clambered over this fallen tree at least twice today already. But most of the time you don’t think. No point. Instead, you exist in a kind of mobile Zen mode, your brain like a balloon tethered with string, accompanying but not actually part of the body below. Walking for hours and miles becomes as automatic, as unremarkable, as breathing. At the end of the day you don’t think, “Hey, I did sixteen miles today,” any more than you think, “Hey, I took eight-thousand breaths today.” It’s just what you do.”

“I mention all this to make the point that if you were designing an organism to look after life in our lonely cosmos, to monitor where it is going and keep a record of where it has been, you wouldn't choose human beings for the job.But here's an extremely salient point: we have been chosen, by fate or Providence or whatever you wish to call it. It's an unnerving thought that we may be living the universe's supreme achievement and its worst nightmare simultaneously.Because we are so remarkably careless about looking after things, both when alive and when not, we have no idea-- really none at all-- about how many things have died off permanently, or may soon, or may never, and what role we have played in any part of the process. In 1979, in the book The Sinking Ark, the author Norman Myers suggested that human activities were causing about two extinctions a week on the planet. By the early 1990s he had raised the figure to about some six hundred per week. (That's extinctions of all types-- plants, insects, and so on as well as animals.) Others have put the figure ever higher-- to well over a thousand a week. A United Nations report of 1995, on the other hand, put the total number of known extinctions in the last four hundred years at slightly under 500 for animals and slightly over 650 for plants-- while allowing that this was "almost certainly an underestimate," particularly with regard to tropical species. A few interpreters think most extinction figures are grossly inflated.The fact is, we don't know. Don't have any idea. We don't know when we started doing many of the things we've done. We don't know what we are doing right now or how our present actions will affect the future. What we do know is that there is only one planet to do it on, and only one species of being capable of making a considered difference. Edward O. Wilson expressed it with unimprovable brevity in The Diversity of Life: "One planet, one experiment."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.We have arrived at this position of eminence in a stunningly short time. Behaviorally modern human beings-- that is, people who can speak and make art and organize complex activities-- have existed for only about 0.0001 percent of Earth's history. But surviving for even that little while has required a nearly endless string of good fortune.We really are at the beginning of it all. The trick, of course, is to make sure we never find the end. And that, almost certainly, will require a good deal more than lucky breaks.”

“But that's the glory of foreign travel, as far as I am concerned. I don't want to know what people are talking about. I can't think of anything that excites a greater sense of childlike wonder than to be in a country where you are ignorant of almost everything. Suddenly you are five years old again. You can't read anything, you have only the most rudimentary sense of how things work, you can't even reliably cross a street without endangering your life. Your whole existence becomes a series of interesting guesses.”