New medical technologies promise to let us mold our bodies at will. Should we use them?

In December 2019, the Chinese ­biophysicist He Jiankui was sentenced to three years in prison for using CRISPR technology to edit the genomes of twin babies conceived in vitro, to make them resistant to the HIV virus. His action was widely condemned for its ethical implications, not least that the risk of editing the children’s genetic code could have unforeseen consequences for their health. Nevertheless, many experts predict that gene editing will sooner or later become acceptable practice. In 2020, a panel of experts argued that while the world “was not yet ready for gene-edited babies,” approval procedures should be developed for such time that “technical hurdles were cleared and societal concerns were addressed.”1

Why is it assumed that “societal concerns” about CRISPR babies will eventually be addressed? I think the assumption stems from deep roots in modern culture, in a way that another recent controversy helps illustrate. In 2015 the Italian surgeon Sergio Canavero gave an interview to Newsweek in which he spoke of his hopes of developing head transplants for human beings. Head transplants could be used as therapy for many conditions, Canavero said, including gender dysphoria.

Canavero’s hopes may remain a fantasy, but they illustrate a typically modern attitude toward human nature, which joins together a desire to dominate nature through human reason with an embrace of subjective feelings of authenticity. This modern synthesis of rationalism and irrationalism has for many people come to seem as matter-of-course as the air we breathe. Yet it is riven by deep contradictions – and contradicts, too, the basic teachings of Christianity.

One way of understanding modernity, indeed, is as a re-interpretation of the Christian doctrine of the lordship of man over the visible creation, including himself. This is a re-interpretation, however, that radically distorts what lordship over nature means. In the Christian tradition, man has only a relative and limited lordship over his body, which he has received from his Creator to be tended in accordance with the purposes and potentials that God has laid into it. But in the modern synthesis of rationalism and irrationalism, man is absolute lord over his body – a body that he may, and perhaps must, change in accord with his authentic inner feelings.

Taquen, The Past, acrylic on handwoven fabric All artwork by Taquen. Used by permission from the artist.

Descartes’s Divided Reality

The rationalist half of the modern synthesis can be traced back to René Descartes (1596–1650). A key figure in the development of modern science, Descartes also developed a metaphysical foundation for it. The details of his metaphysics were discarded by later thinkers, but some of its key premises were preserved. The old “scholastic” science had been ordered to the contemplation of the truth for its own sake. But Descartes (following Francis Bacon) thought the new science should be ordered to lordship over nature. Thus Descartes writes:

[New notions in physics] opened my eyes to the possibility of gaining knowledge which would be very useful in life, and of discovering a practical philosophy which might replace the speculative philosophy taught in the schools. Through this philosophy we could know the power and action of fire, water, air, the stars, the heavens and all the other bodies in our environment, as distinctly as we know the various crafts of our artisans; and we could use this knowledge – as the artisans use theirs – for all the purposes for which it is appropriate, and thus make ourselves, as it were, the lords and masters of nature.2

Descartes’s system divides reality into two realms: the purely spiritual realm of the “thinking thing” (res cogitans), and the purely quantitative realm of the “extended thing” (res extensa), that is, the bodily natural world. The human body, as a mere “extended thing,” is thus sharply separated from the human soul. In Descartes’s words:

I can infer correctly that my essence consists solely in the fact that I am a thinking thing. It is true that I may have … a body that is very closely joined to me.… On the one hand I have a clear and distinct idea of myself, in so far as I am simply a thinking, non-extended thing; and on the other hand I have a distinct idea of body, in so far as this is simply an extended, non-thinking thing. And accordingly, it is certain that I am really distinct from my body, and can exist without it.3

Thus the whole corporeal world, including the human body, is seen by Descartes as neutral material to be dominated by the human soul.

Taquen, The Self, acrylic on handwoven fabric

Although later thinkers rejected various parts of the Cartesian system, this thought pattern continues to influence Western culture, as we see in Sergio Canavero. In Canavero the “thinking thing” has come to be identified with the brain, not the soul. Nevertheless, the distinction between “thinking thing” and “extended thing” is preserved. For Canavero human beings are their brains, and their bodies can therefore be switched.

The lordship of Descartes’s “thinking thing” over the physical world is arbitrary; this lord cannot find purposes intrinsic to natural things that could serve as a guide to the exercise of his lordship. He must himself decide what purposes he will impose on natural things, including his own body. Insofar as his “self” is not a part of nature, he has no reason to pursue “natural” goals. C. S. Lewis points out that this raises a problem:

The final stage is come when Man by eugenics, by pre-natal conditioning, and by an education and propaganda based on a perfect applied psychology, has obtained full control over himself. Human nature will be the last part of Nature to surrender to Man.4

CRISPR technology holds the potential for the kind of thing that Lewis was describing: to control and alter human nature. The scientists who exert such control over a baby’s genome are imposing their own ends on him – ends that may or may not be beneficently motivated, but are accountable only to them:

The Conditioners, then, are to choose what kind of artificial Tao [set of ethics or values] they will, for their own good reasons, produce in the Human race. They are the motivators, the creators of motives. But how are they going to be motivated themselves?5

Lewis shows that as soon as an objective natural order of purposes, goals, and goods has been abandoned, man has no reason to choose x rather than y. All that remains is arbitrary will based on subjective feelings.

Everything except the sic volo, sic jubeo [“thus I desire, thus I command”] has been explained away.… When all that says ‘It is good’ has been debunked, what says “I want” remains.6

Such a completely arbitrary ethic is, however, not satisfying. Hence it is not surprising that pure Cartesian rationalism is generally combined in our times with a quite different ethic: the Romantic ethic of authenticity.

Taquen, Memory, acrylic on handwoven fabric

The Romantic Reaction

Romanticism (in a wide sense) began as a reaction against the reductive materialism of the Enlightenment. Many Enlightenment thinkers after Descartes abandoned the spiritual side of his system of thought. For thinkers such as Thomas Hobbes and Julien Offray de la Mettrie (and for contemporary philosophers such as Daniel Dennett, who take on the mantle of cognitive science, as well as for psychologists including B. F. Skinner) there is no “thinking thing”: everything is pure extension. Human consciousness is an illusion produced by mechanical reactions of matter.

The Romantics protested against such reductionism: No! There is more to the human spirit than that. They did not, however, understand that “more” as something with a stable nature – in the way that Christians understand the soul, for example – but as a dynamic possibility. Jean-Jacques Rousseau wrote of an “inner voice” of nature. Unlike the tradition going back to Aristotle, he did not understand natural beings as having purposes or ends that must guide their development if they are to thrive. Rather, for him this “inner voice” is a creative principle which itself brings purpose into existence.7 This idea was further developed by Johann Gottfried Herder and the Romantics, in ways described by the philosopher Charles Taylor:

Fulfilling my nature means espousing the inner élan, the voice or impulse. And this makes what was hidden manifest for both myself and others. But this manifestation also helps to define what is to be ­realized.… This obviously owes a great deal to Aristotle’s idea of nature which actualizes its potential. But there is an importantly different twist. Where Aristotle speaks of the nature of a thing tending towards its complete form, Herder sees growth as the manifestation of an inner power (he speaks of “Kräfte”), striving to realize itself externally.8

This view is certainly appealing in contrast to the mechanistic alternative, but it is nevertheless wrong. In contrast to Aristotle’s understanding of nature as having intrinsic meaning and purpose, the Romantic understanding of the inner voice of nature leads to subjectivism: each human person must give authentic expression to his or her particular inner voice. Moral goodness consists not in pursuing the goals of a common human nature, but in creatively developing one’s authenticity, a personalized telos which each must discover or create.

There is certainly something of the truth here; we are called upon to cooperate in our own formation. Contra the Romantics, though, our natures are not infinitely malleable, to be formed and re-formed by the arbitrary dictates of our will. We learn who we are not through gazing at ourselves, but through our relationships with others, through common experience of human nature, through the development of virtues. We learn how to tend our bodies and honor them through perceiving them as good, as what we are given.

The synthesis of the Romantics’ celebration of authenticity with Descartes’s rationalism finds a fitting if obviously extreme symbol in Canavero’s suggestion of head transplant as a treatment for gender dysphoria. According to this way of thinking, which is held by many far more mainstream than Canavero, a man who feels the inner voice telling him that he is a woman must follow it in order to live an authentic life. He must exchange his body for a woman’s body. Barring such a radical and clearly impossible solution, he may alter his existing body to become more feminine. His feeling of disjunction is powerful, painful, and real. Although this feeling is quite independent of the natural tendencies of his body, it gives a powerful motive for action: a Romantic motive to seek authenticity by way of the Cartesian action of lordship over nature.

Here then is a prime example of Cartesian rationalism becoming the instrument of Romantic irrationalism. The brain plays the role of the “thinking thing,” which has absolute lordship, even tyrannical lordship, over the body as extended thing. It does not see the body as part of the self, with its own good nature to be tended and honored – and so it can go so far as to change which body belongs to it.

To be sure, modern medicine changes human bodies all the time, in ways most reasonable people are grateful for – for example, through bone-marrow transplants, cleft-palate surgery, or indeed certain kinds of hormonal treatments. Yet there is a vast difference between changing a body for therapeutic ends – to restore it to its natural function – and changing a body to alter its very nature.

Even in drawing the line against any drastic and irreversible changes, the proper response to persons experiencing dysphoria – persons created in the image of God – is compassion and mutual care within a community in which all are valued and beloved members. There is a tradition older than Cartesian rationalism or Romanticism that offers a more coherent account of the nature of body and soul. This same tradition directs us to bear each other’s burdens in a spirit of practical, self-sacrificial love, and commands respect for the dignity of the human person. This is the tradition we turn to next.

Taquen, Remnants of a Wild Garden I, acrylic on handwoven fabric

Lordship in Christianity

The Christian view diverges sharply from the modern synthesis of Cartesian rationalism and Romanticism. Unlike Romanticism, Christianity understands creation as deeply rational through and through, an expression of the wisdom of the Creator. Yet unlike Cartesian rationalism, Christianity sees the lordship of human beings over creation as legitimate only in relation to the Creator’s wisdom: human beings must rule creation in accordance with its deep orderliness, helping natural things achieve the purposes for which they were created.

In the creation story in Genesis, God appoints man as lord over other creatures in God’s stead: “Then God said, ‘Let us make man in our image, after our likeness; and let them have dominion over the fish of the sea, and over the birds of the air, and over the cattle, and over all the earth, and over every creeping thing that creeps upon the earth’” (Gen. 1:26). Over the centuries, Christian tradition has sought to explore what man’s calling to dominion means. Thomas Aquinas, in particular, brings the insights of Aristotelian philosophy and Roman jurisprudence into fruitful dialogue with the biblical account of lordship.

Aquinas expounds his theology of creation with the help of Aristotle’s understanding: man is a unity of matter and form, body and soul.9 Neither is complete in itself; they are only complete in their unity. Further, Aristotle suggests four causes to explain the whys of existence. A statue may be explained in part by its material, “marble,” or by its form, “a young man.” We might point to the agent who made the statue, “Praxiteles,” or to the purpose that the agent had in mind when he shaped the matter into that form: “the honor of the god Hermes.”10 It is this “final cause,” the cause of causes, for which a thing exists and without which none of the other causes have effect.11 The good is the greatest of the causes: first in intention, though often last to come about in reality, as when the statue is set up in the temple.

For Aquinas, the causality of the good is found not only in human action, but in all natural causality. Everything must have an end, or it would neither exist nor act. Every natural thing has a nature, a principle of activity ordered to its end. Each thing strives in accordance with its nature for its own completion, and for the kind of activity that is proper to it. A tree grows, stretches out its branches, and photosynthesizes; it does what a tree does. Human beings can understand the end toward which nature orders them and strive consciously to achieve it: they must in a sense cooperate in their own completion. This understanding of the human end is not an invention or a creation, but the discovery of something inscribed in our nature by our Creator. The end he gives us is to do truly human activities well – to act wisely, justly, courageously, generously, and moderately. Aquinas describes this natural tendency toward the good as the art of our Creator:

Nature is nothing other than the reason (ratio) of a certain kind of art, namely God’s art, impressed upon things, whereby those things are moved to a determinate end. It is as if a shipbuilder were able to give timbers the wherewithal to move themselves to take the form of a ship.12

God has absolute lordship over all creation, because he created and sustains all things, and is their first principle and last end. He gives to all creatures their being, their nature, and their ends. He inscribes their purposes within them, and moves them towards those purposes. Creatures, on the other hand, can only have a relative and limited lordship over anything. Just as God is the universal cause so God is the universal Lord, while creatures are particular lords, whose lordship depends on God’s.

Human beings have direct lordship over their own moral actions, since they cause them by their intellect and will. This lordship – freedom – can only be rightly exercised in accord with the prior Lordship of God. But human beings have only an indirect lordship over their own bodies. In the words of the Thomist philosopher Henri Grenier:

Man has not direct and absolute dominion over his own life and members, but only the guardianship and use of them. For life and body are prerequisites of man’s dominion, and are its foundation. Hence they are not subject to man’s dominion.13

As the guardians of our bodies, the Christian tradition teaches, we must tend them in accord with the purposes that the universal Lord of all has inscribed into them.

In 2011, Pope Benedict XVI gave an address to the German Parliament. The Pope praised the ecological movement which has been active in German politics since the 1970s, celebrating the renewed respect for the natural world, and the concern to protect it from pollution and destruction. This movement, the Pope argued, correctly identified a problem with the way moderns relate to the natural world: we regard it as mere material to exploit for our own ends. This can lead only to destruction; we must instead learn to respect the dignity of nature. He then, however, pointed out a certain inconsistency in the movement – it does not go far enough when it fails to recognize the implications of respect for nature’s dignity for our understanding of humanity:

I would like to underline a point that seems to me to be neglected, today as in the past: there is also an ecology of man. Man too has a nature that he must respect and that he cannot manipulate at will. Man is not merely self-creating freedom. Man does not create himself. He is intellect and will, but he is also nature, and his will is rightly ordered if he respects his nature, listens to it and accepts himself for who he is, as one who did not create himself. In this way, and in no other, is true human freedom fulfilled.

This is of course the idea which Benedict’s successor Pope Francis developed more fully in his encyclical Laudato si’. True freedom for all human beings, true liberation from all that wrongly constrains us and robs us of our happiness, can only arise from a deep respect for the nature given to us by God. We will only be free when we see both our souls and our bodies as gifts to be developed in accordance with the deep wisdom that makes them what they are.


  1. Andrew Joseph, “Expert panel lays out guidelines for germline editing, while warning against pursuit of ‘CRISPR babies’,” Stat, November 3, 2020.
  2. René Descartes, Discourse on the Method, Part 6, AT 6.61–62, in The Philosophical Writings of Descartes 1, trans. John Cottingham et al. (Cambridge University Press, 1985), 142–143.
  3. René Descartes, Meditations on First Philosophy, Meditation 6, AT 78, in The Philosophical Writings of Descartes 2, 54.
  4. C. S. Lewis, The Abolition of Man (MacMillan, 1947), 37.
  5. Lewis, The Abolition of Man, 39.
  6. Lewis, The Abolition of Man, 40.
  7. See Charles Taylor, Sources of the Self: The Making of the Modern Identity (Harvard University Press, 1989), chapter 20.
  8. Taylor, Sources of the Self, 374–375.
  9. Thomas Aquinas, Summa theologiae, Ia, q.76.
  10. Aristotle, Physics 194b-195.
  11. Thomas Aquinas, Summa theologiae, Ia, q.5, a.2, ad 1.
  12. Thomas Aquinas, In octo libros Physicorum Aristotelis expositio, Lib. II, lectio 14, n. 8.
  13. Henri Grenier, Thomistic Philosophy 3 (St. Dunstan’s University, 1949), 187.