Driving home from the airport last week, I caught an interview with the founder of the Voluntary Human Extinction Movement, a group whose goal is to extinct humans by means of a universal, voluntary, self-imposed ban on human reproduction. In this interview (and on the official website), Mr. Knight was claiming human extinction was the morally correct choice for the human race. His implicit syllogism, as best as I can make out, goes somewhat like this:

1. Biodiversity is good.
2. Human reproduction inevitably leads to decreasing biodiversity.
3. Therefore, humans should work towards the goal of zero-reproduction.

(Strictly speaking, this conclusion doesn’t follow without the additional premise, ‘Humans “should” do what is “good,’ but given that most people define ‘good’ as ‘what humans should do’, I have left this premise out for sake of brevity.)

Why Knight is so focused on humans in particular, I can’t say, since the reproductive dominance of any species in a world with finite resources must lead to a decrease in biodiversity. Life on planet Earth consists solely of organisms that tire ceaslessly to turn as much of their environment as possible into copies of themselves. Humans are just spectacularly good (and inefficient) at the whole process.

But the larger gripe I have with Knight’s argument stems from my objection to the notion of intrinsic good. I categorically deny that anything is ‘good’, and instead insist only that things are good to someone (God, if you are a theist). In other words, ‘good’ and ‘bad’ are terms that quantify a being’s reaction to the pleasantness of something. Moral imperatives such as, ‘I should do X,’ then reduce to, ‘I believe that doing X will make me happier than not doing X’ (possibly in the long run, and not the short term), with the implicit assumption that people seek to maximize their own happiness.

With this in mind, I interpret Knight’s syllogism as follows:

1. Biodiversity is good to me.
2. Human reproduction inevitably leads to decreasing biodiversity.
3. Therefore, humans should work towards the goal of zero-reproduction.

In this form, the conclusion does not follow from the premises, even granting they are both true. Knight’s preference for a rich and diverse biosphere implies only that he believes he would be happy attaining the goal of zero-reproduction. It certainly does not imply the happiness of anyone else—and, consequently, does not imply that anyone else ’should’ (under my definition) strive for zero-reproduction.

Another interesting point about the VHEM movement is that it seems doomed to fail at the hands of social and natural selection. Anyone who believes in VHEM will not reproduce, and will therefore die out. The people who don’t believe in VHEM will survive and raise children, most of whom will end up sharing the beliefs of their parents. In this way, the VHEM movement might naturally lead to the extinction of itself, but not to that of the human race. (Whether or not VHEM will truly die out depends on the conversion rate of non-VHEM individuals to VHEM supporters; but in any case, I can hardly imagine such a movement growing indefinitely, or even for very long.)