This is on the ‘values’ side of ‘metaphysical values, rather than the ‘metaphysical’; but I will talk about 'in virtue of', so I don't feel totally ashamed :-)
We are doing a reading group on abortion, and today we were reading Liz Harman’s ‘The potentiality problem’. Harman is interested in how to defend the position that says both that early term abortions are morally permissible and that harms to human babies are worse than harms to, say, cats.
If early term abortions are morally permissible (and not just because not aborting would result in some greater evil, such as the death of the mother) then it seems they are so because the embryo has no moral status. But the baby appears to have moral status, if harming it is worse than harming the cat, so we need an account of what it takes to have moral status that lets the baby in but not the embryo (and it may or may not let the cat it). Harman proposes the following principle:
Conscious: A being has moral status at t just in case it is ever conscious and it is not dead at t.
(She should add ‘and it exists at t’ I think, but let’s not quibble.)
Since I am conscious, the embryo that I was (assuming that I was a embryo) had moral status. But since an embryo which is aborted is not conscious at any time, it does not have moral status at any time, and so it is permissible to abort it.
So I’m permitted to abort this embryo because it lacks moral status, but the reason that it lacks moral status is precisely because I aborted it: had I not aborted it, it would (at least, so we can suppose) have been conscious at some time, and so would have had moral status as an embryo. So I’m permitted to do this action because of something that is only true because I do this action – I don’t like it!
Consider another case. Suppose the moral oracle (completely trustworthy on all moral issues) tells us that it’s really, really bad to utter falsehoods. So bad, in fact, that if someone utters a falsehood, it’s permissible to kill them. Now I ask you what you’re going to do tomorrow and you say ‘I’m going to the cinema’. And then I shoot you. I was perfectly justified, because you spoke falsely: you’re not going to the cinema tomorrow, because tomorrow you will be dead! But intuitively, even in the world in which uttering falsehoods is a bad punishable by death, I shouldn’t be justified in punishing you for something that was only the case because I punished you.
The worry is this. In the ‘falsity is bad’ world, the proposition [it is permissible to kill a] is true in virtue of [a told a falsehood]. But [a told a falsehood] is true in virtue of [I killed a]. So it looks like the ultimate basis for the truth of [it is permissible to kill a] is in [I killed a]. And that looks absurd: my carrying out an action shouldn’t be what makes it the case that I was permitted to carry out that action.
Likewise, for Harman, [it is permitted to abort embryo e] is true in virtue of [e is never conscious] which is in turn true in virtue of [I abort e]. So it looks like the ultimate basis for the truth of [it is permitted to abort embryo e] is in the truth of [I abort e]. And that looks totally wrong to me: my carrying out the abortion shouldn’t make it the case that I was justified in carrying out the abortion.