Péter Kakuk raises several important questions in his commentary on our paper on viruses and fetuses, life and abortion. We are delighted to have this opportunity to reiterate and clarify some of our main points.
In the title of the paper, we posed a very specific conditional question and offered an equally specific conditional answer. The question was: if viruses are not life forms, should abortion always be permitted? Generally speaking, the answer depends on two variables: the interpretation of viruses as non-life forms and the view taken on the permissibility of abortion.
We opted for the 2025 Encyclopedia Britannica view, according to which “viruses are parasites […] relying entirely on their [hosts] for [their lifelike] functions [and this] supports the classification of viruses as nonliving entities”. This characterization may, of course, be superseded as science advances, but that would have no bearing on our present analysis, which remains conditionally valid. To complete the comparison with human fetuses at their earlier developmental stages, we “only” need to ascertain that similar vocabulary can meaningfully describe them.
In his commentary, Kakuk points out that dependence on the help of others is not limited to viruses and fetuses, and that our analogy may go too far. “Newborn infants, severely disabled people, coma patients, and patients on artificial life support may all depend on external systems or other persons.” While this is true, extending the analogy in this way is not supported by the language of our Encyclopedia Britannica citation. Members of the groups listed do not rely entirely on hosts for their life-sustaining biological processes; the external support they require is to maintain vital functions defined by their own autoteleonomy.
Kakuk further notes that dependence is not the only reason for the exclusion of viruses from the sphere of living things: “They are also acellular, lack independent metabolism, and do not maintain homeostasis in the way organisms do, and do not develop into non-dependent organisms”.
In the first three of these criteria, there seems to be an important equivocation between being biologically alive at the cellular level and being a living organism in the morally relevant sense invoked by our limited framework of “another life” in someone else's body. Every cell in our bodies is cellular, metabolically active, and homeostatically regulated, yet none is considered a living being for the purposes of our target argument.
As for Kakuk's fourth criterion, the prospect of becoming something else has been addressed in two main ways in the abortion debate. Those with permissive views have held that even if beings belonging to category non-X (non-self-aware, non-sentient, non-living) could develop into beings belonging to category X (self-aware, sentient, living), this does not in itself warrant special treatment for them. We gestured in this direction by referring to Michael Tooley's classic example of miracle kittens, but, it transpires, too inconspicuously. Those with restrictive views have regarded potentiality more favourably, but their considerations have typically arisen within the Aristotelian setting that we have argued makes no decisive contribution to our life/non-life distinction.
Abortion can, as Kakuk rightly observes, be rejected on many grounds, some of which concern the moral status of fetuses. Since we have not covered all these grounds, the general answer to our title question must, accordingly, be negative. Even if viruses were not life forms, this would not prove that abortion should, in all possible moral frameworks, be permitted. This in itself is a modest conceptual result, but then we proceed to a further one. There is at least one framework – the “my life, my choice” versus “but there is another life involved” clash – within which a modified Aristotelian reading of metaphysics yields our projected conclusion. Bearing in mind that at least Thomistic Neo-Aristotelians have traditionally taken a very dim view of permitting abortion, this is interesting. Or so we think.
Kakuk's conclusion is that we would benefit from arguing, not that fetuses fail to be life forms, but rather that “mere biological life is insufficient for moral status” or that “the category of life is too ambiguous to ground anti-abortion arguments by itself”. We agree – and thought that our persistent use of “if” had made this evident, despite the bolder claims appearing within the confines of the philosophical conditionals. Our bad.
In sum, then, following Kakuk's points. The vitality of viruses has many definitions. True, and we have chosen a fairly authoritative one. Fetuses are not exactly like viruses. True, and we have concentrated on the features they have in common. Fetuses are not the only dependent beings. True, and we have tried to show how their dependence is closer to that of viruses than to that of the beings in Kakuk's examples. We have not shown that abortion should always, from every viewpoint, be permitted. True, but we have demonstrated how it could be permitted within a hostile tradition, in response to an argument used within and around that same tradition. That is a limited but potentially explosive conceptual outcome, one that gains strength from Péter Kakuk's insightful comments and, we hope, our responses to them.