The key element of Don Marquis argument is in the effort to distinguish the difference between abortion and contraception in order to provide a clear argument against abortion, aside from extreme cases. Without conflicting with the interest of the general public by being forced to suggest contraception is ethically wrong as well. When he compiles his argument he begins by providing the argument for a ‘pro-choice’ approach which makes the assumption that a fetus is a being but one who's life is not ethically applicable and can be ended without moral consequence. This gives us an insight into the apparent symmetry between this set of ideals in contrast with the beliefs of the ‘anti-abortion’ approach which views a fetus as a being, ones who’s life is ethically applicable and cannot be ended without moral consequence. The conflicting issue being weather or not a fetus falls under the category of a morally applicable ‘sentient being’ and this, in turn, is what Marquis sets out to confirm in order to create a solid case for the ‘anti-abortion’ approach.
He accepts that logically if either of these arguments are to be convincing it needs to extend beyond normal social moralities. For instance an anti-abortion argument cannot simply rely on the age old conception that "It is always prima facie seriously wrong to take a human life" or "It is always prima facie seriously wrong to end the life of a baby." as both of these understandings cannot be ridiculed. The pro-choicer argument in and of itself will make a similar claim that is once again supported by the moral principles in society such as; "Being a person is what gives an individual intrinsic moral worth" or "It is only seriously prima facie wrong to take the life of a member of the human community." which also poses a parallel but opposite problem.
While the anti-apportion scope is too broad, covering ‘all life‘ the pro-choice argument is too narrow