Robert George and Christopher Tollefsen do a fine job of responding to William Saletan’s arguments against their book Embryo. Saletan identifies features of embryological development that, to his mind, tell against the notion that human embryos are whole living human organisms; George and Tollefsen refute his arguments. (Saletan has written a rejoinder.) I want to make three additional points, all of which concern the conclusion of Saletan’s review: “We should never create or destroy embryos lightly. We owe them our respect. We just don’t owe them the same respect we owe one another.”

First: While many people find the notion of an intermediate moral status for the embryo attractive, the decision we are trying to make is basically binary: Either killing those embryos for our purposes is permissible or it is not. If it is permissible, then in no important respect does the embryo have a moral status above that of a mere thing. To put it another way, its supposedly higher status does it no good.

Second: Those closing lines make it sound as though Saletan wants us to proceed with embryo-destructive research, but with fear and trembling. But as Saletan himself points out at the start of the review, we are talking about routinized mass production and destruction of embryos. Assuming that we begin this enterprise with whatever amount of hand-wringing Saletan considers desirable, how likely is it that the hand-wringing will continue?

Third: We can easily get tripped up by the question of whether the embryo is our moral equal–whether, as Saletan puts it, we “owe them the same respect we owe one another.” The key question is not whether the embryo is our equal in all ways but whether it is our equal in one precise way: in, that is, having a right not to be deliberately killed. Human beings in the embryonic stage of development may be very unlike human beings in later stages of development in all kinds of ways, and some of those differences may have moral implications. The issue is whether any or all of those differences justify allowing human beings in early stages of development to be killed.