Thomson and those following her have famously argued that even if a fetus possessed a right to life comparable to that of a typical adult human being, many abortions would still be permissible.One important line of objection to the Thomson arguments is the Responsibility Objection (RO):Responsibility objection: If a person engages in voluntary sex with the knowledge that a fetal person in need of aid will, or might, result, and a fetal person in need of aid does result, the person has a special obligation to provide aid to the fetal person."Special obligation" here means an obligation attaching to the parents in particular, an obligation beyond that which any stranger would have for a person in need.RO does not necessarily make any claim that voluntary sex implies or constitutes tacit consent to provide aid. It might claim only that having voluntary sex with the knowledge that a fetus might result is sufficient to make one liable to provide aid if a fetus results. That is, it might claim that voluntary sex is akin to negligence in ordinary tort cases.RO is intuitively plausible. Certainly, it captures a widely and strongly held judgment about responsibility for the persons that result from voluntary sex, particularly in the case of fathers. Even if a father scrupulously uses birth control, and even if he in no way consents to the care of a child that accidentally results, the fact that the father engaged in voluntary sex with the knowledge that a needy person might result is sufficient reason, in the view of most people, to obligate the father to care for the child. 1 Silverstein, and Boonin in his recent book, attack RO. 2 Each man provides a negative argument against grounds for RO. Each also provides a positive argument for the conclusion that even if a person has voluntary sex with the knowledge that a fetal person in need might result, and a fetal person in need does result, the person has no special obligation to provide aid to the fetal person. Although the negative and positive arguments are similar, the positive arguments are intrinsically more interesting and make it easier to articulate my line of reply. So, I will be interested exclusively in the positive arguments in what follows. 3 Silverstein's and Boonin's positive arguments are also much alike, so I will consider them together, as a single argument.Their positive argument appeals to cases of the extension of the life of an existing person. These cases have an important feature in common with cases