In the past I’ve argued that it may be possible to build a basic system of ethics by looking to our evolutionary background to discover what sort of behaviour is natural for humans. This is a natural law approach which looks to our evolutionary heritage to discover the essential nature of humans.
Robert George’s work is an example of how far this approach can go wrong. Robert George is a Christian philosopher, but he argues that his approach to ethics is based on what is natural for humans without relying on any specifically Christian notions. He has a complex argument in this mode for why homosexual marriage is unethical. I can not do justice to his argument, but the essential points are that the reproductive-type behaviour is what we are designed to seek, that it leads to a natural unification of male and female which is desirable, that this behaviour is good even if no reproduction can result due to infertility, that other types of sex are not natural, and that the law must teach people to have natural sex.
I don’t agree with this argument but I’m not going to try to pick it apart, especially since I’m not presenting it completely. What it shows, though, is the inherent difficulty with any natural law approach, which is similar to the inherent difficulty with any argument based on sociobiology or evolutionary psychology: there is a very strong tendency to first pick the result that you want, and then develop an argument which supports it. In other words, I don’t think George is acting as a I think a natural law philosopher should: drawing conclusions from data, rather than developing data to support a conclusion.
Fortunately I don’t think this has to be a fatal problem with the overall approach. I think it is possible in principle to avoid this typical error, and to examine human behaviour and evolutionary heritage without preconceptions. This means approaching the problem the way an ideal scientist does. Unfortunately it is impossible, or at any rate unethical, to conduct direct experiments on human behaviour. However, it is possible to conduct indirect experiments by studying different human societies. For example, there have been a number of societies which tolerated and even encouraged homosexuality, and John Boswell has argued that even the early Christian church had formalized relationships between male couples.
It remains open to question whether we can get anything really useful from this approach. The main use of ethics is to guide us in ambiguous situations. Any argument based on evolution is inherently messy and contingent, rather than based on simple principles which can be built into complex predicates. Our evolutionary past gives us no guidance on questions like the proper use of state surveillance.
I’m still attracted to the idea in part because I can’t think of anything else. I don’t believe that pure moral relativism is psychologically coherent. I think that human societies must have some ethical system in order to function. I don’t think we can develop an ethical system based on pure reason, or, rather, I believe we can develop many such systems, but I don’t see how to make any particular one more convincing than any other. So I’m left with trying to base a system on our nature, and that comes from evolution.
On the other hand, it’s possible to argue in principle that some form of utilitarianism can serve as the basis of an ethical system. That troubles me in a couple of ways. Firstly, we have to decide how to measure utility. It is typically defined in terms of happiness, but that assumes that we can know what that is, and we need some way to distinguish between the pleasure of the moment and longer term satisfaction. At some point we come back to trying to figure out what people really want.
Secondly, utilitarianism makes it easy to support actions which violate the rights of the few in favor of the utility (however measured) of the many. You can try to work against this by including specific rights in your utility measure, but there is no obvious way to determine what those should be, and it makes the utilitarian arguments more ambiguous and thus less useful. While historical human societies obviously present no good argument for equal treatment for all humans, I think they do present a good argument that every person has certain rights and expectations within their own sphere, and those rights are only abrogated in extreme circumstances, circumstances exceeding those of mere utility maximization. (Of course this argument only holds for people considered to be part of the tribe, not for people considered to be less human; these days I think most of us consider all of humanity to be members of our tribe.) What this argument suggests to me is that this failing of utilitarianism is a real failing when it comes to applying it to human society.
Getting back to natural law, what I’m suggesting is that ethical philosophers, and indeed all of us, need to look to our past to determine the guidelines for moral behaviour. In other words, anthropologists should be the new ethicists.