There are certain responses to the arguments in my post, “The Meat Eaters,” that recur with surprising frequency throughout the comments. The following four objections, listed in the order of the relative frequency of their appearance, are the most common.
1. If predators were to disappear from a certain geographical region, herbivore populations in that area would rapidly expand, depleting edible vegetation, and thereby ultimately producing more deaths of among herbivores from starvation or disease than would otherwise have been caused by predators. And starvation and disease normally involve more suffering than being quickly dispatched by a predator.
2. Should human beings be the first to go?
3. What about the suffering of plants?
4. What about bacteria, viruses, and insects?
My own response will focus primarily on the first of these objections, and on the ways in which the argument might continue after the objection has been noted.
In the sixth, seventh, and eighth paragraphs of my original article, I anticipated the first objection. I wrote:
Suppose that we could arrange the gradual extinction of carnivorous species, replacing them with new herbivorous ones. Or suppose that we could intervene genetically, so that currently carnivorous species would gradually evolve into herbivorous ones, thereby fulfilling Isaiah’s prophecy. If we could bring about the end of predation by one or the other of these means at little cost to ourselves, ought we to do it?
I concede, of course, that it would be unwise to attempt any such change given the current state of our scientific understanding. Our ignorance of the potential ramifications of our interventions in the natural world remains profound. Efforts to eliminate certain species and create new ones would have many unforeseeable and potentially catastrophic effects.
Perhaps one of the more benign scenarios is that action to reduce predation would create a Malthusian dystopia in the animal world, with higher birth rates among herbivores, overcrowding, and insufficient resources to sustain the larger populations. Instead of being killed quickly by predators, the members of species that once were prey would die slowly, painfully, and in greater numbers from starvation and disease.
After presenting the objection, I referred back to it six times in the course of the remaining 1900 words of the article. Those references typically stress that my argument takes a conditional form: that is, my argument has practical implications only if we could have a high degree of confidence that problems of the sort I identified could be avoided. Yet this same objection is repeatedly pressed in the comments, usually with lamentations over my appalling ignorance of biology and ecology, as if I had been unaware that there was such an obvious and devastating refutation of everything I had said. I will return to this fact about the nature of the commentary at the end of this response.
Among those commentators who actually read the article and thus were aware that I had acknowledged the objection, a few took the argument a step further. They understood that my argument was conditional but claimed that the relevant condition could never obtain. We will never, they contended, be able to eliminate predation without causing catastrophic ecological disruption and thus even more suffering than we might have prevented. If they are right, my article may present an interesting thought experiment that might have prompted us to reflect on our values (though it didn’t), but it is essentially devoid of practical significance. These readers were too polite to point out that their prediction also casts Isaiah in a pretty disappointing light in his role as prophet.
My assumption in the article, however, was that our understanding of the biological and ecological sciences may well advance beyond what we consider possible today. That has happened repeatedly in the history of science, as when Rutherford, who first split the atom, said in 1933 that anyone who thought that the splitting of the atom could be a source of power was talking “moonshine.” Since we can’t be certain that we’ll never be able to reduce or eliminate predation without disastrous side effects, it’s important to think in advance about how we might wisely employ a more refined and discriminating power of intervention if we were ever to acquire it.
It seems, moreover, that my argument has some relevance to choices we must make even now. There are some species of large predatory animals, such as the Siberian tiger, that are currently on the verge of extinction. If we do nothing to preserve it, the Siberian tiger as a species may soon become extinct. The number of extant Siberian tigers has been low for a considerable period. Any ecological disruption occasioned by their dwindling numbers has largely already occurred or is already occurring. If their number in the wild declines from several hundred to zero, the impact of their disappearance on the ecology of the region will be almost negligible. Suppose, however, that we could repopulate their former wide-ranging habitat with as many Siberian tigers as there were during the period in which they flourished in their greatest numbers, and that that population could be sustained indefinitely. That would mean that herbivorous animals in the extensive repopulated area would again, and for the indefinite future, live in fear and that an incalculable number would die in terror and agony while being devoured by a tiger. In a case such as this, we may actually face the kind of dilemma I called attention to in my article, in which there is a conflict between the value of preserving existing species and the value of preventing suffering and early death for an enormously large number of animals.
Many of the commentators said, in effect: “Leave nature alone; the course of events in the natural world will go better without human intervention.” Since efforts to repopulate their original habitat with large numbers of Siberian tigers might require a massive intervention in nature, this anti-interventionist view may itself imply that we ought to allow the Siberian tiger to become extinct. But suppose Siberian tigers would eventually restore their former numbers on their own if human beings would simply leave them alone. Most people, I assume, would find that desirable. But is that because our human prejudices blind us to the significance of animal suffering? Siberian tigers are in fact not particularly aggressive toward human beings, but suppose for the sake of argument that they were. And suppose that there were large numbers of poor people living in primitive and vulnerable conditions in the areas in which Siberian tigers might become resurgent, so that many of these people would be threatened with mutilation and death if the tigers were not to become extinct, or not banished to captivity. Would you still say: “Leave nature alone; let the tigers repopulate their former habitats.”? What if you were one of the people in the region, so that your children or grandchildren might be among the victims? And what would your reaction be if someone argued for the proliferation of tigers by pointing out that without tigers to keep the human population in check, you and others would breed incontinently and overcultivate the land, so that eventually your numbers would have to be controlled by famine or epidemic? Better, they might say, to let nature do the work of culling the human herd in your region via the Siberian tiger. Would you agree?
In fact we can’t leave nature alone. We are a part of it, as much as any other animal. More importantly, we can’t help but have a massive and pervasive impact on the natural world given our own numbers. Agricultural practices necessary for our survival constitute a continuing invasion and occupation of lands previously inhabited by others. One explicit suggestion of my article was that it would be better to try to control our impact on the natural world in a purposeful way, guided by intelligence and moral values, including the value of diminishing suffering, rather than to continue to allow our effects on the natural world, including the extinction of species, to be determined by blind inadvertence — as, for example, in the case of the many extinctions of animal species that will be caused by global climate change.
Some commentators made the interesting point that even if predators were to become extinct in a certain area without environmental catastrophe, new ones would eventually evolve there to fill the ecological niche that would have been left vacant, thereby restarting the whole dreary cycle. But even if this were to happen, the evolution of a species can take a long time, and a lengthy interval without predation could be a significant good, just as the prevention of a war can be a great good even if it does nothing to prevent other wars in the future. More importantly, it’s hardly plausible to suppose that we could have the ability to eliminate a predatory species from an area but would then lack the ability, even in the distant future when our scientific expertise would have advanced even further, to prevent a new predatory species from arising.
Consider the three other responses that turned up repeatedly in the comments. Some readers suggested that my argument implies that we should aim for the extinction of the carnivorous human species, the species that that causes far more suffering to other animals than any other species. Most took that to be a reductio ad absurdum of my argument, but a few seemed to think that getting rid of human beings would be a good idea. For those who wish to pursue this issue, I recommend Peter Singer’s contribution to The Stone (“Should This Be the Last Generation?”, June 6, 2010). My own response can be quite brief. Human beings are not carnivores in the relevant sense, but omnivores, and in most cases can choose to live without tormenting and killing other animals, an option that is not a biological possibility for genuine carnivores. My own view, though I won’t argue for it here, is that the extinction of human beings would be the worst event that could possibly occur.
What about the suffering of plants? Again a brief response: plants don’t suffer, though they do respond to stimuli in ways that some have mistaken for a pain response. What was rather shocking about the repeated invocation of suffering in plants is that it occasioned no reflections on what the moral implications would be if plants really did suffer. The commentators’ gesture toward the alleged suffering of plants seemed no more than a rhetorical move in their attack on my argument. But if one became convinced, as some of the commentators appear to be, that plants are conscious, feel pain, and experience suffering, that ought to prompt serious reconsideration of the permissibility of countless practices that we have always assumed to be benign. If you really believed that plants suffer, would you continue to think that it’s perfectly acceptable to mow your grass?
Finally, my responses to the recurring challenges concerning microbes and insects parallel those I offered to people’s solicitude about plants. Like plants, microbes don’t suffer. I don’t think we know yet whether many types of insect do. If, in controlled conditions, one pulls the leg or wing off a fly while it’s feeding or grooming, it will carry on with its activity as if nothing had happened. But suppose insects really do suffer, perhaps quite intensely. Shouldn’t that elicit serious moral reflection rather than being deployed as a mere debating point?
Earlier I noted that by far the most common objection to my article was that I ignored the likely consequences of the elimination or even the mere reduction of predation. If you have the patience, review the first 152 comments on my article. You will find this objection stated in 28 of them — that is, in one of every 5.4, or nearly 20 percent. Given that I explicitly stated and addressed that objection, and later reverted to it six times, it seems clear that many, and probably most, of the readers of the article gave it only a cursory glance before pouncing on their keyboards to give me a good roasting. But at least those who replicated the objection I had stated deserve credit for saying something of substance. What’s particularly disheartening is that their comments are greatly outnumbered by those that make no reference to my arguments and never touch on a point of substance, but instead consist entirely of insults and invective. If you take your own moral beliefs seriously, the way to respond to a challenge to them is to make sure you understand the challenge and then to try to refute the arguments for it. If you can’t answer the challenge except by mocking the challenger, how can you retain your confidence in your own beliefs?
Jeff McMahan is professor of philosophy at Rutgers University and a visiting research collaborator at the Center for Human Values at Princeton University. He is the author of many works on ethics and political philosophy, including “The Ethics of Killing: Problems at the Margins of Life” and “Killing in War.”