“Why Not Let Life Become Extinct?”

Symbols of death in a painting: it shows a flower, a skull and an hourglass

John Leslie (1940 – ) is currently Professor Emeritus at the University of Guelph, in Ontario, Canada. In his essay “Why Not Let Life Become Extinct?” he argues that we ought not to embrace the view that extinction would be best.

Some argue that it would not be sad or a pity if humans went extinct because: 1) there would be nobody left to be sad; or 2) life is so bad that extinction is preferable. Leslie maintains that this issue has practical implications since someone with power might decide that life is not worth it, and press the nuclear button (or bring about some other extinction scenario.) Fortunately, most do not reason this way, but if they do there is a paucity of philosophical arguments to dissuade them. Moreover, philosophers often advance arguments that we should improve the lives of the worst off and, since so many people live wretched lives, it is easy to see that a solution might entail killing a lot of people.

But what of letting all life go extinct? Some philosophers argue that we have no duty to prevent this, that even if life is good we have no duty to propagate it, or if someone is about to lose their life we have no obligation to save it. The principle behind such thinking is that though we ought not to hurt people, we have no duty to help them. Other lines of thinking may lead to similar conclusions. A utilitarian might argue that life should go extinct if it is sufficiently unhappy now or will be so in the future. Others argue that we have no duties to produce future people no matter how happy they might be, for the simple reason that these possible people cannot be deprived of anything, as they do not yet exist. Leslie counters that deciding whether to produce a situation should be influenced by what the situation will be like, by its consequences. If one is deciding whether to produce a certain future, the most relevant fact is whether that future will be good.

He now makes some concessions. First, it is morally good to want to make the lives of the worst-off better, but not if this entails destroying the entire human race. Second, actual people are not obligated to make all sacrifices for possible people, any more than you are obliged to give food to others when your own family is starving. Third, given overpopulation, we are not obligated to have children.

And since ethics is imprecise, we cannot be sure that we have duties to future generations. Still, the universe has value despite the evil it contains, leading Leslie to speculate that there might be an “ethical requirement that it exist…”[i] In other words a thing’s nature, if it has intrinsic value, makes its existence ethically required. But how can the description of a thing’s nature lead to the prescription that it ought to exist? Leslie argues that we cannot derive that a thing should exist from a description of its nature. Perhaps it would be better if no life existed. But suppose we agree that life is intrinsically good, would we then have an obligation to perpetuate it? Leslie answers no. A thing’s intrinsic goodness only implies some obligation that it exists, since other ethical considerations might overrule that obligation. For instance, a moral person might think it better that life ended than have a world with so much suffering. The upshot of all this is that there are no knockdown arguments either way. Competent philosophers who argue that it is better for there to be no life probably are on equal footing with those who argue the opposite. Leslie continues: “Still, pause before joining such people.”[ii]

In the end, we cannot show conclusively that we should not let life become extinct because we can never go from saying that something is—even happiness or pleasure—to saying that something should be. And it is also not clear that maximizing happiness is the proper moral goal. Perhaps instead we should try to prevent misery—which may entail allowing life to go extinct. Philosophers do not generally advocate such a position, but their reluctance to do so suggests that they are willing to tolerate the suffering of some for the happiness of others.

Summary – There are strong arguments for letting life go extinct, although Leslie suggests we generally reject them because life has intrinsic goodness.


[i] John Leslie, “Why Not Let Life Become Extinct?” (1983) in Life, death, and meaning, ed. David Benatar (Lanham, MD.: Rowman & Littlefield, 2004), 128.
[ii] Leslie, “Why Not Let Life Become Extinct?” 130.

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2 thoughts on ““Why Not Let Life Become Extinct?”

  1. A few points of fact:

    1. The problem facing the human race in the near future is not overpopulation but underpopulation. Our entire civilization is based on an implicit assumption of continual growth, but in fact fertility rates in all the developed economies have now fallen below the replacement rate. Were it not for immigration, the populations of all the developed nations would be falling. As underdeveloped nations improve their lot, their own fertility rates will fall. Demographics estimate that the global population will peak at around 10 billion sometime in mid-to-late century, then begin to fall. This will create all sorts of new problems, the most pressing of which will be the collapse of pension systems based on the scheme of using taxes from young workers to sustain retired older people.

    2. It is beyond our capability to destroy all Homo sapiens. Yes, an all-out nuclear war would kill a billion or so people immediately, and kill most of the rest over the next few years, but it would be impossible to kill every last person. There would always be survivors in remote locations. The Inuit and the Lapps, for example, would be well out of the way of most fallout, and are quite capable of surviving a nuclear winter. The Southern Hemisphere would have no combatants in a nuclear war and would largely be spared the destruction. The most likely outcome of a nuclear war (and in fact, the most likely fate of humanity under any circumstances) is a return to the hunter-gatherer lifestyle for which the species evolved.

    3. Lastly, if anybody is worried about the elimination of all life on this planet, well, forget it. If we devoted our entire energies to that goal, we could not have the slightest hope of achieving it. The biosphere is far too resilient.

  2. Chris, thanks as always for your keen insights. I knew point 1 but forgot to include it. (2 heads are better than 1). I’ve thought a lot about the southern hemisphere for that very reason but believe it or not your location is one of the best in the continental USA.

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