I find that there’s often a crucial assumption implicit in discussions of abortion ethics. It comes up at mentions of when personhood arises in the development from zygote to fetus to baby. One person claims that some particular moment is the threshold at which personhood arises. The other points out that zooming in to that moment and looking at extremely nearby moments, we see no particular reason to privilege one over the others. This arbitrariness is taken to be a fatal blow for the account of personhood.
This raises an interesting question. Could the fundamental moral laws be arbitrary? By analogy, think about the laws of physics. The laws of physics contain certain parameters like the gravitational constant G and me/mp, the ratio of the mass of an electron to the mass of a proton, whose values are likely arbitrary to some degree. Even taking into account fine-tuning for life, it’s probable that the fine-tuning isn’t infinitely precise and there’ll be some level of arbitrariness in the 1000th decimal place value of G.
If the laws of physics can be arbitrary, why not the laws of morality? Perhaps there’s just one arbitrary point at which moral personhood emerges, and there’s not much motivation for that point over any other. How strange you consider this to be will likely depend on what your meta-ethical theory is. Trivially, if you don’t think there are moral facts at all, then this puzzle never even arises for you. If you think there are moral facts, but there’s somehow socially or biologically determined, then it’s not so puzzling that there would be arbitrariness in the moral facts. But if you’re a moral realist that believes in an objectively true set of laws governing morality, then this view starts to look strange.
Among moral objectivists, it seems to me like anti-Humeans would not be okay with arbitrariness in the laws of morality. In meta-ethics, anti-Humeans are those who believe that moral facts are intrinsically motivating. This doesn’t mesh well with arbitrariness. If the moral laws are arbitrary, then why should I follow them rather than a neighboring set of laws that work just as well? Almost by definition, arbitrariness in the moral laws implies a lack of motivation, both motivation for the letter of the laws and motivation to live by the laws. On the other hand, if one takes a Humean stance on meta-ethics, perhaps arbitrariness is not so puzzling.
Moral arbitrariness might also be troubling to divine command theorists, who believe that the moral rules are set by God. There’s something that seems quite strange about saying that God’s commands are arbitrary to some extent (though to be fair, I say this from a very atheistic perspective, so perhaps my intuitions differ from theists here). But if this feels strange, then why shouldn’t it feel just as strange to say that the laws of the physical universe are arbitrary? Presumably God also decided on the precise values of all the physical parameters, and there seems to be arbitrariness there. Is there something particularly troubling about the idea that God’s choice of moral laws is arbitary?
Moral arbitrariness seems like an inevitable consequence of most, maybe all, moral systems. A rights-based approach has to deal with tradeoffs between different rights: how severe a breach of bodily autonomy is severe enough that it’s better to violate a person’s right to life? Any binary account of personhood seems bound to end up drawing the line at some arbitrary point. And gradualist accounts of personhood come with their own type of arbitrariness: why should the curve of increasing personhood with time look like precisely this, rather than some other very similar curve? Virtue theoretic approaches talk about virtues arising in a happy medium between two vices (e.g. bravery arising between cowardice and foolhardiness), but where is the precise middle point? If one were to completely codify virtue ethics, they would have to say precisely what level of riskiness is bravery, and when it tips over into foolhardiness. But there will always be thought experiments that place you just barely on either side of this threshold and reveal that there is no apparent moral difference between one side and the other.
Perhaps the framework that has the least trouble with moral arbitrariness is consequentialism. Something like utilitarianism says that the threshold for when you should choose Act 1 over Act 2 is exactly when the expected net utility produced by Act 1 exceeds the expected net utility produced by Act 2 (where utility is something like “happiness minus sadness”). Unfortunately, I think that this approach runs in to problems as well. Happiness is not one-dimensional, and neither is suffering. How do you make different types of happiness commensurable? How many sips of hot chocolate are equivalent to a roller-coaster ride? How many minutes in front of a fire on a cold night are equivalent to the moment of insight when you solve a tough mathematical problem? I find it hard to imagine that non-arbitrary answers to these types of questions exist.
If it’s true that most all moral frameworks contain fundamental arbitrariness, as I believe it is, then I think that this turns into a powerful argument against many types of moral realism. If you’re an anti-Humean, then you have to either deny the arbitrariness or explain why arbitrary moral laws would be intrinsically motivating to us. If you think that God created the moral laws, then you have to reckon with the apparent arbitrariness of those laws. Presumably God always makes the optimal choice when one exists, but what does God do when faced with a choice where there is no optimum?