Marquis: a defense of abortion?

This is a reply to Don Marquis' "Why Abortion is Immoral." Marquis, who asserts that abortion is morally wrong, bases his argument on the following premise: Killing a being is morally wrong if that being is the sort of being who has a valuable future. I argue that this premise is false. I then assert that if I am correct about this premise being false, Marquis is faced with a dilemma. If he does not alter the premise in a way that makes it true, his argument is unsound. However, if he does make such an alteration, he must also alter a second premise in his argument, and this second change opens him to the charge of question begging. In addition, I conclude that such an alteration requires Marquis to adopt a position much like that taken by Judith J. Thompson in "A Defense of Abortion," a position he initially states is indefensible.