Best explanation and sexual ethics

Consider three ethical claims about sexuality:

1. Rape is always wrong.

2. Incest is always wrong.

3. Bestiality is always wrong.

Take these claims in the strong sense: they hold genuinely always, no matter what the circumstances. Rape is wrong even if the victim is in a coma, is unharmed physically, permission is given by a proxy, and nobody (including the victim) ever finds out. Incest is wrong even between consenting adult relatives raised apart, with no chance of conception. Bestiality is wrong no matter whether the animal is aware of the event, and no matter how low on the evolutionary scale the animal falls or how much the animal wants the act. All these things are wrong even if much rides on them: they are wrong even to save multiple lives, including the life of the victim in case (1).

Now, although it is easy to find ethical views of sexuality that explain why rape, incest and bestiality are almost always wrong, it is hard to find coherent and well-developed views that explain why these are always wrong. But such views do exist. I know of two families of them: there are traditional natural law views and there are views like those of Karol Wojtyla which meld natural law with personalism (my One Body is in this category). However, these two families of views also entail highly controversial further prohibitions on unmarried sexuality, artificial contraception and same-sex sexual activity.

This yields an indirect inference to best explanation argument for the controversial further prohibitions: the best views we have that explain (1)–(3) also entail these further prohibitions.

Of course, one can try to turn the argument around. But I think generally speaking we have better epistemic access to what is forbidden than what is permissible, and so arguing from commonly accepted prohibitions to controversial prohibitions is better than arguing from commonly accepted permissions to controversial permissions.

I am not saying that those who deny the controversial prohibitions need to deny that (1)–(3) are exceptionlessly true to be consistent. I am just saying that they probably aren't going to have a good explanation for why (1)–(3) are exceptionlessly true.

A form of explanation in ethics

Why are murder and incest wrong? Here are plausible things to say:

1. Murder is wrong because it cuts short a future life of valuable agential activity.
2. Incest is wrong because it leads to genetic defects in offspring.

Now an explanation needs to be true. But murder doesn't always cut short such a future life (e.g., think of the murder of a severely disabled person) and incest doesn't always lead to genetic defects (e.g., suppose the two parties are past the age of childbearing or are of the same sex). So the explanations in (1) and (2) must be understood as making Aristotelian categorical claims, like "Sheep have four legs", claims that are true in normal or paradigm cases. On the other hand, the claims on the left side, that murder and incest are wrong, are meant to be true in all cases. Thus, (1) and (2) can be made more explicit as:

3. Murder is always wrong because normally it cuts short a future life of valuable agential activity.
4. Incest is always wrong because normally it leads to genetic defects in offspring.

Now, it seems that there is something deeply fishy about (3) and (4). How can the fact that normally murder and incest result in certain grave harms explain the fact that they are always wrong? Yet, murder and incest are always wrong, and the harms cited seem to have something to do with their wrongness. One could say that the harms cited explain only the wrongness of normal cases of murder and incest, and other cases are wrong due to other harms. But I do not think this is desirable. Similar worries are likely to apply to the other harms. Maybe one can find a set of such harms such that every possible case of murder or incest is made wrong by something in the set, but that is not so likely. One could, I suppose, abandon the claims that murder and incest are always wrong, but that's a serious moral mistake.

But on a number of ethical theories the explanations in (3) and (4) are perfectly fine.

Rule utilitarianism: Here the point is clear: an act can be wrong precisely because most of the time it is seriously harmful.

Divine command: Because the acts result in such terrible harms in most cases, God wants us to stay far away from these acts and wisely forbids them to us in all cases. So the fact that normally great harms result explains God's universal prohibition, which in turn grounds the universal wrogness.

Natural law: The natures of things support their flourishing as individuals and as a kind. That an action type is normally harmful to the individual or the kind makes it likely that the action type is unnatural, and hence wrong. This explanation becomes more satisfactory, I think, on a theistic natural law theory. For then we can explain why it is that the natures of things support their flourishing. On a view on which God designs natures, one can say that God is unlikely to design a nature that fails to support the flourishing of an individual or kind. On a view on which God finds (in his mind) natures and then decides which natures should be exemplified in creatures, one can say that God is unlikely to choose to exemplify natures that do not support the flourishing of the individuals or kinds. On a non-theistic natural law theory, it may be a bit more puzzling why the natures of things support their flourishing. Maybe an evolutionary explanation can be given, though.

Notice an interesting difference. In an appropriate rule utilitarianism the harm facts might ground the wrongness facts. In the divine command and natural law cases, they don't ground the wrongness facts, but explain them in a less direct way.

In all of these cases, the same line of thought that leads to the explanations allows for the following argument:

5. Action type A normally produces great harms.
6. So, A is always wrong.

On an appropriate rule utilitarianism, this could be a deductively valid argument. But on the other theories, it is only a defeasible inference.

Templates for relationships

I wonder if human nature might not come along with a finite number of more or less flexible normative templates for love-relationships. These templates would define the basic forms of love that are appropriate to us. An attempt to create new basic relationships, or to transcend the boundaries between these, would then be failures insofar as a relationship is defined normatively. Thus, two siblings might attempt to enter into a romantic relationship, and they might behave romantically together. But, nonetheless, they would not be having a romantic relationship, because the normative features of a romantic relationship would be objectively absent: thus, there would in fact be no obligation—but only a false belief in the obligation—to nurture the kind of intimacy that a romantic relationship calls for. We would say that the siblings are not in a valid romantic relationship, where we use "valid" in the technical sense in which we say that only an "invalid promise" (i.e., no promise at all, but only the appearance of one) results from coercion.

One way to make plausible such a story would be through a scepticism about the possibility of our creating new normative facts, other than by simply by making the antecedents of pre-existing conditional ones true.

Of course the difficulties then are epistemological: how do we know what all the templates are?