Every one of us began our existence as an embryo. The embryo we were was not an entity distinct from us; it was us. Sure, as an embryo we did not exhibit the same properties we do today, but we did possess those properties intrinsically as part of our nature. This invites a question to the pro-abortion advocate: If it is wrong to kill me now (as a child/adult), how could it have been permissible to kill me then (as an embryo/fetus)? Both instances involve the same entity. The unborn differ from the born in their stage of development, not their kind, much the same way newborns differ from adults in their stage of development, not their kind. If we recognize the latter, why do so many deny the former?

To escape the force of this logic the pro-abortion advocate is faced with a couple of recourses. He could admit that the same entity is killed in both instances, but that the stage of development does matter when determining who the recipient of a right to life is and who is not. Killing a human entity in its earliest stages of development is morally permissible precisely because they are not yet fully developed. This response encounters many difficulties: (1) it would justify killing newborns and teenagers because they are not fully developed yet either; (2) it capitalizes on the ambiguity of what it means to be fully developed; (3) it begs the question as to how one stage of development can give someone value over another stage; (4) it falls prey to the problem of authority, because who gets to decide which stages of development are value-laden and which ones are not?

Most will take a different route. They will admit that the same entity is killed in both instances, but killing an embryo/fetus is justified because they do not yet possess the value-defining attributes of personhood. While they are human beings, they are not human persons. They claim value is found in function, not essence.

These are philosophical assumptions that needs to be demonstrated. One cannot simply presuppose that one can be a human being without being a human person, or that value is determined by function. Do these ideas stand the test of reason? No. Some of the difficulties associated with this view are as follows: (1) it suffers from the problem of authority, because who is to say which properties are value-defining and which are not?; (2) it is circular in its reasoning because the criteria for personhood are defined in such a way so as to exclude the unborn from the start, but then used as justification for abortion; (3) the criteria not only deprives the unborn of his value, but the newly born as well, making infanticide morally acceptable; (4) it undermines our intuitive notion of human equality because if value is defined by function, and humans exhibit different levels of functioning, then it follows that humans possess differing levels of value. It seems best to understand personhood—and hence value—to be a property that inheres in human beings from the moment they begin to exist onward.

It stands, then, that to kill the unborn is morally equivalent to killing the born. If the latter is evil, so is the former.