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.With the exception of a concern with insects, the last three objections are (it seems to me) stupid. But apparently they have been made often, so McMahan is probably right to respond to them. His response to the first objection is that he already addressed this and argued, basically, that we should phase out carnivores only if we can do so without doing more harm than good. Saying that we cannot do so does not prove him wrong. It does potentially make the whole exercise a bit pointless, but McMahan has a response to this. Speaking of people who make this objection, he writes:
2. Should human beings be the first to go?
3. What about the suffering of plants?
4. What about bacteria, viruses, and insects?
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.So, how does the article make us reflect on our values? Or rather, what do we see when we reflect? McMahan's values seem to be both anthropocentric (I think he would accept this) and utilitarian in a pretty straightforward, Benthamite sense (I think he would accept this too). Mine, I find, are much less anthropocentric and more religious/aesthetic/Nietzschean. So perhaps his article has value because of the clarificatory role it can play.
At the end of this new article he writes:
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?This sounds like the kind of thing that Cora Diamond responded to in her paper "Anything but Argument?" It also reminds me of the question of foundationalism. McMahan seems to want rational justification of our moral beliefs all the way down. But that's not possible. Arguments start with premises, and these cannot all be proved by yet more arguments whose premises are in turn supported by sound arguments, etc. So we have to start somewhere. McMahan seems to start with the ideas that pain is bad and pleasure is good, although in this case his focus is on the badness of pain. But it's very hard to say what pain is, or what pleasure is. And all sorts of bad things seem to exist that are not pain (grief, despair, loneliness, regret, itching, frustration, anger, injury, insult, etc. etc.). If we define 'pain' as 'bad feeling' then many of these things might count as pains, but the word 'bad' is surely hard to define. And do we really have a good understanding of what exactly a feeling is? I'm sure that attempts to reduce the concept of pain to something that fits a naturalistic ontology (such as the opposite of preference satisfaction) have been made, but it seems like a hopeless project to me. (I realize that I should do some reading before making a final verdict on the matter.) If the goodness of the natural world more or less as it is is as obvious to someone as the badness of pain is to McMahan, then how can that person respond to his arguments without insults and invective? What can be said except: "Are you blind?" We could try taking him to a zoo, or giving him some good books to read, but I wouldn't have much hope that such things would make a difference to him.
So he's disheartened and I'm disheartened. Maybe it's time to talk about something else.