When I published what was to become an influential paper on the therapy-enhancement distinction in human genetics over two decades ago,Reference Resnik ¹ the enhancement debate was mostly concerned with the morality of manipulating the human genome to produce children with desired characteristics, i.e., “designer babies.” Since then, the debate has expanded beyond the genomic realm to encompass different enhancement technologies (e.g., neural implants, neuropsychiatric drugs, and artificial intelligence) and enhancement purposes (e.g., for combat performance, space exploration, or longevity). The literature on this topic is now vast and often byzantine and esoteric.

For example, the debate about whether society should enhance moral behavior in human beings is, in my judgment, a quixotic distraction from real-world enhancement questions, such as whether astronauts should be physically enhanced for space exploration.Reference Szocik ² We don’t know what it would mean for a human being to be morally enhanced or how to use technology to safely and effectively produce morally “superior” people.Reference Wiseman ³ Morally enhanced people could turn out to be docile lemmings who follow rules assiduously but have no sense of individuality; or conversely, Nietzschean Übermenschen who believe that they have the right to rule the rest of us.

Likewise, the transhumanism movement, which aims to leave behind the human body and psyche and initiate the rise of post-humans, is, in my judgment, out of touch with social and technological realities and moral common sense. Transhumanists fail to appreciate the seriousness of the harms that could occur to individuals and society if Homo sapiens were to become a polymorphic species composed of humans and post-humans. Modest enhancements of the immune system to help people ward off infectious diseases or fight cancerReference Juengst ⁴ are a far cry from the radical proposals defended by transhumanists, such as greatly extending the human lifespan, supercharging human cognitive abilities, or merging human beings with machines.

In his insightful paper “Moral Permissibility and Desert in the Therapy-Enhancement Distinction,” Ozan Gurcan takes a fresh look at the therapy-enhancement distinction and argues that, while the distinction does not establish rigid moral boundaries, it nevertheless serves an important purpose because it differentiates between interventions that are, generally speaking, owed to individuals as a matter of justice (i.e., therapies) and those that are not (i.e., enhancements). Because therapies help to promote justice in society, therapies are always permitted and, in many cases required, whereas enhancements may be, at best, permitted. Framing the distinction in this way “signals to us that more vigilance is warranted for enhancements — even though there is nothing intrinsically immoral about them — so we can address novel concerns that may arise.”Reference Gurcan ⁵

In my opinion, Gurcan provides a rigorous analysis of the therapy-enhancement debate that engages important work on the topic and offers some useful guidance for policymakers. Although I agree with Gurcan that it is important to consider how interventions may impact social justice when deciding whether they should be permitted, required, or perhaps prohibited, I wonder if our concerns about the morality of enhancement extend beyond its effect on the distribution of social and economic goods in society. Wouldn’t we be concerned about enhancement even if did not exacerbate social and economic inequalities? I think we would.

During the 1990s and early 2000s, I gave little credence to arguments, such as those advanced by bioconservatives like Kass,Reference Kass ⁶ that human nature provides a basis for morally distinguishing between therapy and enhancement. While I still hold that there are some significant conceptual problems with moral naturalism, not the least of which is how to bridge the logical gap between prescriptive and descriptive statements, I now am much more sympathetic to this view than I once was.Reference Lutz ⁷

Events and trends that have occurred in the last two decades have caused me to rethink my views about moral naturalism. We are much closer to transcending humanity today than when I wrote about this topic 25 years ago. Our social-technological environment includes AI-powered chatbots and robots; AI-generated text, artwork, music, and video; virtual reality games, communities, and pornography; sophisticated disinformation campaigns run by governments, businesses, and political organizations; extreme human body modification and cosmetic surgery; and highly innovative, technologically-assisted reproduction. We can now see more clearly what it might mean to radically change our humanness, and the picture the emerges is often not pretty and at times terrifying. We need moral signposts — including biologically-based ones — to help us navigate through a chaotic and dynamic world in which it is becoming increasingly difficult to distinguish between reality, artifact, and illusion.

While I am not claiming that biology is the only guide to morality, I do think it plays an important role in shaping our moral judgments, emotions, and behavior.Reference Fuchs ⁸ Our moral sensibilities are based, at least in part, on facts of human biology, including our anatomy, physiology, mortality, vulnerability, family structures, sociality, and sexuality.Reference Greene ⁹ Consider, for example, the notion of human rights. A strong argument can be made that our intuitions about the meaning and scope of human rights are based, at least in part, on a prior understanding of facts about human biology. The right not to be killed presumes that we are mortal; the right not to be harmed presumes that we are vulnerable; the right to freedom of movement presumes that we can move about physically; and the right to reproduce presumes that we are capable of reproducing by ourselves.

I am not sure how people would treat each other if the human form were radically altered. I am not convinced that abstract notions of rights, duties, virtue, and justice would be sufficient to guide us if we were to release ourselves from the biological anchor that has secured us throughout history. It is of course possible that, over time, we will evolve as a species and acquire new moral sensibilities that will guide us through new environments. However, natural selection is far slower than technological innovation and making radical changes to ourselves in a short time span may be too much for us — as a species — to handle. Given these uncertainties, the wisest course of action would be to permit minor modifications to the human form to produce benefits that are demonstrable and uncontroversial (such as a disease prevention) but not to pursue the radical revision or replacement of humanity envisioned by some transhumanists.Reference Resnik ¹⁰

Thus, while I agree with Gurcan that the concept of justice serves as signpost for drawing a rough distinction between therapy and enhancement, I propose that other key moral ideas, such as the concept of human nature, may also be important in establishing this boundary. Future work in this area could explore the role of different moral theories and concepts in framing therapy/enhancement policies.