I claim that the standard objections to the Potentiality Argument (PA) are very weak and can be answered. This is especially so with respect to Joel Feinberg's "logical point about potentiality," which alone I will discuss in this post. This often-made objection is extremely weak and should persuade no rational person. But first a guideline for the discussion.
The issue is solely whether Feinberg's objection is probative, that and nothing else. Thus one may not introduce any consideration or demand extraneous to this one issue. One may not demand of me a proof of the Potentiality Principle (PP), to be set forth in a moment. I have an argument for PP, but that is not the issue currently under discussion. Again the issue is solely whether Feinberg's "logical point about potentiality" refutes the PA. Progress is out of the question unless we 'focus like a laser' on the precise issue under consideration.
The PA in a simplified form can be set forth as follows, where the major premise is the PP:
1. All potential persons have a right to life.
2. The fetus is a potential person.
3. The fetus has a right to life.
What Feinberg calls the "logical point about potentiality" and finds unanswerable is "the charge that merely potential possession of any set of qualifications for a moral status does not logically ensure actual possession of that status." (Matters of Life and Death, ed. Regan, p. 193) Feinberg provides an example he borrows from Stanley Benn: A potential president of the United States is not on that account Commander-in-Chief of the armed forces.
It seems to me that Feinberg's objection, far from being unanswerable, is easily answered. Let me begin by conceding something that is perfectly self-evident, namely, that inferences of the following form are invalid:
4. X is a potential possessor of qualifications for a certain moral or legal status S
5. X is an actual possessor of qualifications for status S.
This is a glaring non sequitur as all must admit. If x potentially possesses some qualifications, then x does not actually possess them. So of course one cannot infer actual possession from potential possession. A five-year-old's potential possession of the qualifications for voting does not entail his actually having the right to vote.
But what does this painfully obvious point have to do with PP? It has nothing to do with it. For what the proponent of PP is saying is that potential personhood is an actual qualification for the right to life. He is not saying that the fetus' potential possession of the qualifications for being a rights-possessor makes it an actual rights-possessor. He is saying that the actual possession of potential personhood makes the fetus a rights-possessor. The right to life, in other words, is grounded in the very potentiality to become a person.
What Feinberg and Co. do is commit a blatant ignoratio elenchi against the proponents of PA. They take the proponent of the PA to be endorsing an invalid inference, the (4)-(5) inference, when he is doing nothing of the kind. They fail to appreciate that the potentialist's claim is that potential personhood is an actual (and sufficient) qualification for the right to life.
Of course, one can ask why potential personhood should be such a qualification, but that is a further question, one logically separate from the question of the soundness of Feinberg's objection.
I have just decisively refuted Feinberg's "logical point about potentiality" objection. What defenders of it must do now, without changing the subject or introducing any extraneous consideration, is to tell me whether they accept my refutation of Feinberg. If they do not, then there is no point in discussing this topic further with them. If they do, then we can proceed to examine other objections to PA, and the positive considerations in favor of PA.