Consider this standard story:
Whatever value fetuses have derives from their potentiality (and here various distinctions matter) to grow into humans that actually have various valuable features, features that are not simply potentialities. Typical human adults actually have the valuable features that ground their moral status, while fetuses only potentially have these features. The question of the moral status of the fetus, then, is the question of how far their potentiality makes it possible to extend to them the moral status that typical human adults have (and, likewise, to extend the moral status of typical human adults to atypical ones).
I have argued in earlier posts that the kind of potentiality fetuses have does call for the extension of moral status. But I now wonder if this whole line of thought doesn't presuppose a mistaken view, namely that the moral status of typical human adults is grounded in the actual possession of valuable non-potentiality features. Specifically, I worry that this line of thought has too optimistic a view of the human race.
The feature of human beings that matters most centrally seems to be the moral life. But in practice our moral life just isn't all that good. We are full of self-deceit, akrasia and dollops of malice, in different combinations. Is it really the case that typical human beings are morally good in such a way that their actual moral goodness gives them the kind of moral status we are thinking about?
And in any case, even if, say, 70% of adult human beings do have such moral goodness, what about those of us who are in the other 30%? They, too, have moral status. No matter how many crimes one has committed previously, no matter how wicked one is, one has the moral and legal right to a fair trial, to a punishment that does not exceed the gravity of the offense.
What I said about the moral life also goes for the intellectual life: the typical human's intellectual life just isn't much to be proud of. Just think of all the fallacious forms of reasoning we engage in. Plus, I do not know how central the intellectual life is to moral status. Suppose there was a race of super-intelligent mathematicians who had no drive but to prove interesting theorems and no moral life to speak of. Would they have the kind of moral status humans have? I don't know. (It could be that they would have to have the rudiments of a moral life, in that they would have to be attuned at least to the values of truth and beauty to practice mathematics well. So it could be that the thought experiment is impossible.)
Now, it may well be that the above thoughts are too pessimistic. The George MacDonad quote here seems quite significant. But I still think this is worth thinking about, and I think there is something to the idea that the moral status of typical adult humans comes not so much from actual valuable properties, but from their innate potentiality for the good moral life. It is what we should (eventually?) be, not what we are, that is central to our dignity on this suggestion.