On a natural law theory of morality, some moral facts are nature-relative, i.e., grounded in the particular kind of nature the particular rational being has, and other moral facts are structural, a part of the very structure of rationality, and will apply to any possible rational being.
Thus, the norm of monogamy for human beings (assuming, as I think, that there is one) is surely be nature-relative—it seems very likely that there could be rational animals to whom a different reproductive strategy would be natural. But what Aquinas calls the first precept of the natural law, namely that the good is to be pursued and the bad is to be avoided, is structural—it applies to any rational being.
I think that evidence for a human norm being nature-relative is that either the space of norms contains other very similar norms nearby or it’s vague which precise norm obtains. For instance, take the norm of respecting one’s parents. This norm implies that we should favor our parents over strangers in our beneficence. However, how much more should we favor our parents over strangers? If there is a precise answer to that question, then there will be other nearby norms—not human ones—that give a slightly different precise answer (requiring a greater or smaller degree of favoring). On the other hand, that the good is to be pursued does not seem to have very similar norms near it—it has an elegant simplicity that a variant norm like “The good is to be pursued except when it is an aesthetic good” does not have.
I used to think the norms involved in double-effect reasoning were structural and hence applied to all possible rational being. I am no longer confident of this. Take the case of pushing a large person in front of a trolley without their permission in order to stop the trolley from hitting five others. We can now imagine a continuum of cases depending on how thick the clothing worn by the large person is. If the clothing is sufficiently thick, the large person has an extremely small probability of being hurt. If the clothing is ordinary clothing, the large person is nearly certain to die. In between is a continuum of probabilities of death ranging from negligibly close to zero to negligibly close to one, and a continuum of probabilities of other forms of injury. It is wrong to push the large person if the chance of survival is one in a trillion. It is not wrong to push the large person if the chance of their being at all hurt is one in a trillion. Somewhere there is a transition between impermissibility and permissibility. Either that transition is vague or it’s sharp. If it’s sharp, then there are norms very similar to the one we have. If it’s vague, then it’s vague which of many very similar norms we have.
In either case, I think this is evidence that the relevant norm here is nature-relative rather than structural. If this is right, then even if it is wrong for us to push the large person in the paradigmatic case where death is, say, 99.99% certain, there could be rational beings for whom this is not wrong.
This leads to an interesting hypothesis about God’s ethics (somewhat similar to things Mark Murphy has considered):
- God is only subject to structural moral norms and does not have any nature-relative moral norms.
I do not endorse (1), but I think it is a hypothesis well worth considering.
