The question I am trying to answer is whether Don Marquis' argument against abortion is simply a restatement of the potentiality principle. I don't think it is because Marquis does not appeal to personhood.

But, WHY is it important that Marquis doesn't appeal to personhood?

You ask, The question I am trying to answer is whether Don Marquis' argument against abortion is simply a restatement of the potentiality principle. I don't think it is because Marquis does not appeal to personhood----------------------------------------------Marquis’s argument is based on his account of the wrongness of killing. On this account ‘killing someone is wrong, primarily because the killing inflicts (one of) the greatest possible losses on the victim’ — a loss consisting in the fact that ‘when I die, I am deprived of all the value of my future’.In other words, if a being has a highly valuable future ahead of it — if it has a ‘future like ours’ — then death would seriously harm that being (by inflicting a great loss upon it), so that killing it would be prima facie seriously wrong (indeed as wrong as killing you or me). But this account of the wrongness of killing ‘has obvious consequences for the ethics of abortion’:
The future of a standard fetus includes a set of experiences, projects, activities, and such that are identical [in kind] to the futures of adult human beings and are identical [in kind] to the futures of young children. Since the reason that is sufficient to explain why it is wrong to kill human beings after the time of birth is a reason that also applies to fetuses, it follows that abortion is prima facie seriously morally wrong.
Marquis holds that the right to life is generated by the harm of being killed. On his account, death is a harm — hence being killed is a harm — because it deprives the victim of the value of his future: that is, of the total value of future goods (minus future evils) he would have attained if he had continued living.
He uses ‘foetus’ to mean ‘unborn human organism’. A being has a right to life to the extent that killing the being is, in itself, prima facie wrong (that is, prima facie wrong quite apart from any effects of the killing on, or duties owed to, beings other than the one killed). Normal human adults have a full right to life: killing them is prima facie very seriously wrong. My concern is whether the foetus has a right to life in this sense.--------------------------


Of course he sees the fetus as a "person with a future". He just doesn't use the term. "Being", "unborn human organism" All euphemisms, and all tip toeing around the word "person.
However in my opinion his augument from deprivation/ potentiality is flawed.
He takes it upon himself to project the fetuses future. His argument extends into the "what if" realm of possibilty.
No where in his argument does he address the womans concern against the "possible future" of the fetus. I stress possible future because no one can have knowledge of what that future will bring, and the future is what his entire "argument from deprivation/ potentiality" is based on.
Under current law a fetus does not become a "person", with all the rights and privileges of a person, until it leaves the birth canal.

Marquis does not use the potentiality principle. The reasons for killing the adult are the same as the reasons for killing the infant or fetus. It is because a future that is valuable will be loss.

Potentiality arguments state that it is wrong to kill a being with right X and it is also wrong to kill a being that does not have right X, but will have right X in the future.

Marquis does no such thing. He maintains that both the fetus and the adult have attribute X and is is wrong to kill any being with attribute X.

In order to defeat his future argument you would have to argue that fetuses do not have a "future like ours"

There is more about Marquis and abortion here (http://www.hundiejo.com/philosophy/index.php/all?s=marquis&sentence=AND&submit=Search)

I would also like to add, in reference to the first comment that fetuses do not share in some rights of individuals outside the womb. It is still illegal to kill the fetus against the mother's will, and our law does not prosecute such individuals simply on the grounds of damaging of property. The killer is prosecuted as a murderer. The only difference between the unborn terminated by means of a routine abortion and the unborn killed along with its mother in a drunk driving accident or by a stray bullet is that one child was wanted by its mother and the other wasn't.