"Good morning, Dr. Mason."

"Good morning, Dr. Ling. Thank you for taking time to consult with me on Mr. Islan's case."

"Happy to be able to help. So, give me the particulars."

"Islan is a 42-year-old male with advanced arteriosclerosis. If his condition is left untreated, he could suffer cardiac arrest or a stroke at any time. His current health is terrible. He suffers excruciating chest pains and has to restrict his activities drastically – he can barely walk up a flight of stairs, and he has to rest after he does. I don't expect him to live more than another year in this condition. I've talked to him about a regimen of lifestyle modifications, recommending a diet with less than 10 percent total fat and minimal saturated fat, exercise, meditation and other stress reduction techniques. Even though this treatment promises to clear the blockages, improve his quality of life, and allow him to live to a ripe, old age, he's balking. He refuses to make major lifestyle changes. He says he can't, that I'm just asking too much."

"Have you talked to him about surgery, followed by drug therapy and less drastic dietary and behavioral modifications? Less red meat, more chicken, a walking program, that sort of thing?"

"Sure, that's what he wants to do. In his condition, though, that'll just slow the progression of the disease. You know surgery can only clear the worst blockages – we can't clean out every bit of plaque from his arterial system. Without real dietary change and exercise, his body's blood flow will only become more blocked. At best he'll live another two, maybe five, years and his quality of life will continue to deteriorate."

"I hear you, Steve, but you've got to be realistic. If that's all he's willing to do then you'll just have to accept it. Maybe in a few months or a year he'll be ready to do more. You can only do what he'll let you do."

"I guess you're right, but I don't feel like it's enough."

Three years, four months, six days and thirteen hours later, Mr. Islan's heart stopped. He suffered terrible chest pains and weakness up to the end, including every day of the extra two years, four months, six days and thirteen hours that "realism" bought him.

The criticism that one is too much of a "purist" is only valid if the same goals can be met while accepting a lesser standard. If that isn't the case, then one is not a purist but a realist (in the genuine sense). I see no evidence that any standard less than an end to growth will do if our goal is saving the world – and what other goal is worth pursuing?

What, after all, is the problem here? We're in this global crisis because of the rapid, massive expansion of our claim on the biosphere. We've gotten ourselves into this fine mess because the vast majority of the world's human population now lives a single basic lifestyle founded on perpetual growth, and treats the world in a single way – as human property. Despite many differences in detail, at the most basic level of world view and lifestyle most of the six billion or so humans now alive are part of a single culture.

In raw terms, what does our growth mean to the world? Every bit of growing we do depletes the resources some other member of the community of life needs to survive. By our population growth, we are converting ever more of the world's living matter – its biomass – into human living matter, human flesh, and all the resources we use which were living matter: food, trees, medicinal plants, cotton, hemp, and so on. As ever more of the world's biomass is converted into us and our stuff, inevitably ever less of it can be anything else. The world can only support so much total biomass, whether that "anything else" is bald eagles and California condors and gray whales and redwoods, or dung beetles and pallid sturgeon and obscure species of earthworms and plants none of us has ever even bothered to name.

Our growth means more than that, though, because we use enormous amounts of non-living matter to support our lifestyles, too. As we increase our numbers, as we grow, we also increase the amount of inorganic materials we appropriate for human use – fossil fuels, metals, that sort of thing – and consequently increase the damage done in their extraction, processing and use. We and the rest of the community of life are drowning in the waste we've created, and we're shredding the web of life as we strip-mine the planet, devastating ancient, evolved ecosystems every step of the way.

The fact of the matter is that we don't know what the biosphere's limits are. We could be beyond them already, although I certainly hope not (and I behave as though we're not so that I can have hope for the world). If we're not, there's still no way to know just which bit of additional growth will push us over the precipice. Whatever the limits are, our good sense tells us that growth must stop at some point (and probably very soon) if we are to save the world (including ourselves, as we are inextricably a part of it). Perpetual growth on a finite planet is a physical impossibility.

Of course it makes sense to realistically accept that we're not on the verge of convincing the rest of the people of our culture to abandon this growth-bound lifestyle (we don't have to persuade the people of the remaining other cultures – tribal cultures – because they don't live like this). Accepting that which we aren't yet able to achieve, however, is not at all the same as advocating the very thing which is devouring the world (albeit less of it). Our growth is the world destroyer, and I don't think it makes any sense to spend our time trying to convince those around us to pursue a program which at best will only result in our destroying the world at a more leisurely pace. They may not listen to us when we tell them what it's really going to take to turn things around, but at least they'll know what they need to know to make an honest choice.