Sir

Axel Kahn reminds us, rightly, that Kant's famous principle states: “Respect for human dignity requires that an individual is never used⃛ exclusively as a means”, and suggests that I have ignored the crucial use of the term ‘exclusively’ (Nature 388, 320; 1997).

I did not, of course, and I am happy with Kahn's reformulation of the principle. It is not that Kant's principle does not have powerful intuitive force but that it is so vague and open to selective interpretation, and its scope for application is consequently so limited, that its utility as one of the “fundamental principles of modern bioethical thought”, as Kahn describes it, is virtually zero.

Kahn himself rightly points out that debates about the moral status of the human embryo are debates about whether embryos fall within the scope of Kant's or any other moral principles concerning persons; so the principle itself is not illuminating in this context. Applied to the creation of individuals which are, or will become, autonomous, it has limited application. True, it rules out slavery, but so do other principles based on autonomy and rights.

If you are interested in the ethics of creating people, then, so long as existence is in the created individual's own best interests, and so long as the individual will have the capacity for autonomy like any other, the motives for which the individual was created are either morally irrelevant or subordinate to other moral considerations.

So even where, for example, a child is engendered exclusively to provide ‘a son and heir’ (as in many cultures), it is unclear how or whether Kant's principle applies. Either other motives are also attributed to the parent to square parental purposes with Kant, or the child's eventual autonomy, and its clear and substantial interest in or benefit from existence, take precedence over the comparatively trivial issue of parental motives. Either way, the “fundamental principle of modern bioethical thought” is unhelpful.

I am therefore at a loss to know why Kahn invokes it with such dramatic assurance or how he thinks it applies to the ethics of human cloning. It comes down to this: either the ethics of human cloning turn on the creation or use of human embryos, in which case, as Kahn himself says, “in reality the debate is about the status of the human embryo” and Kant's principle must wait upon the outcome of that debate; or it is about the ethics of producing clones that will become autonomous human persons.

In the latter case, as David Shapiro rightly comments (Nature 388, 511; 1997), the ethics of their creation are, from a Kantian perspective, not dissimilar to that of other forms of assisted reproduction or indeed to the ethics of the conduct of parents concerned exclusively with producing an heir or preserving their genes or, as is sometimes alleged, making themselves eligible for public housing — and debates about whether these are exclusive intentions are sterile or irresolvable.

When Kahn asks: “Is Harris announcing the emergence of a revisionist tendency in bioethical thinking?”, the answer must be rather that I am pleading for the emergence of “bioethical thinking ” as opposed to empty rhetoric of invoking resonant principles with no conceivable or coherent application to the problem at hand.