John Leslie’s, “Why Not Let Life Become Extinct?”

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 a 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. Other 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, anymore 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 exist, since other ethical considerations might overrule that obligation. For instance a moral person might think it better that life ended then 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 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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