Will argues that utilitarian ethical paradigms are not viable because they are inconsistent with the way humans actually think: “We are natural-born Aristotelians (or maybe Humean sentimentalists) unlikely to be moved by comprehensive schemes of utility maximization.” A few reactions, not necessarily in a logical order, as this post began as a too-long comment in Will’s comments box. Note: none of the following should be taken as an endorsement of the pure-Benthamite utilitarianism espoused by Layard, to whose position Will was responding.
1. Evolution, whether cultural or biological, operates on the phenotype, not the genotype. Suppose for a moment that selective pressures point in a utilitarian direction because they correspond to utilitarian factors (the need to produce food, clothing, and shelter, for example). I know this is a stretch, but go with me here; even if selective pressures don’t always point in that direction, they sometimes do. Even so, we should not expect evolution to produce a tendency to think in utilitarian terms – it should only produce either motivational states or specific actions that correlate with utilitarian results.
2. People don't usually think like utilitarians, and it's often difficult for them to do so. That, as Will says, puts a constraint on utilitarian theory. Fine. I don't think it follows, as Will says, that the “underlying principles” embodied in the biological constraints “do all the work.” In fact, that’s such a non sequitur that I’m not sure how to respond. It’s similar to saying that when a firm tries to maximize profits, the technology of production does all the work, without the need to ask about consumer demand or the supply of inputs. Moreover, the underlying principles themselves may (I would argue they often do, at least in the case of culturally as opposed to biologically embedded motivations) reflect utilitarian concerns. Yes, people think about the principles as absolutes, but so what? My argument above in (1) says we shouldn't expect cultural evolution to embed utilitarian reasoning so much as utilitarian results.
3. Example: Why do many societies have a moral prohibition on theft? Because in the absence of such rules, great effort will be expended on rent-seeking activities (stealing from others, defending one's own) instead of productive activities. Meanwhile, the marginal return of productive activities is reduced by theft, further reducing the incentive to be productive. So societies that somehow imbue their members with a moral aversion to theft will probably perform better. That's essentially a utilitarian argument for the prohibition of theft, but it doesn't require that individuals carry with them the utilitarian reasoning that supports the prohibition; a simple moral aversion to theft will do. (And before anyone jumps on my case for relying on group selection here, I’ll admit this is an incomplete argument. But I do think group selection can work under limited circumstances; see here and here. And does anyone have a better explanation for why norms against theft are so widespread?)
4. In his comments section, Will says that Joshua Greene’s experiments – which show that people are much more inclined to help people with whom they have personal contact than abstract strangers – show that people are motivated by anti-utilitarian principles. Not necessarily, I say. Any sensible ethical system, including one based on utilitarian concerns, needs to draw on local knowledge. Our knowledge of people in distant places is limited and often untrustworthy, and our knowledge of how best to help them is even more unreliable. So there's a sensible utilitarian justification for having people “take care of their own.”
5. Nonetheless, given our small-group evolutionary heritage, helping very distant strangers probably contributes little to reproductive fitness, so this is a case where evolution is highly unlikely to have equipped us with fully utilitarian norms. To the extent that “ought implies can,” we have to take these built-in anti-utilitarian motivations as given. But this is not an argument against utilitarianism. It's an argument for finding institutions that draw on our built-in motivations in a way that, nonetheless, contributes to the greater good. This is, I think, one reason capitalism is so fantastic: it harnesses self-interest (or small-group-interest) in the service of others, since opportunities to help others so often manifest as profit opportunities.