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Many people feel that being a unique individual is important, and the basic thrust of this first attempt to show that cloning aimed at producing persons is intrinsically wrong involves the idea that the uniqueness of individuals would be impaired in some way by cloning. In response, I think that one might very well question whether uniqueness is important. If, for example, it turned out that there was, perhaps on some distant planet, a person who was qualitatively identical to oneself, down to the last detail, both physical and psychological, would that really make one's own life less valuable, less worth living?

In thinking about this, it is important to distinguish two different cases: first, the case where the two lives are qualitatively identical due to the operation of deterministic causal laws; secondly, the case where it just happens that both individuals are always in similar situations in which they freely decide upon the same actions, have the same thoughts and feelings, and so on. The second of these scenarios, I suggest, is not troubling. The first, on the other hand, may be, but if it is, is it because there is a person who is qualitatively indistinguishable from oneself, or, rather, because one's life is totally determined?

I am inclined to question, accordingly, the perhaps rather widely held view that uniqueness is important for the value of one's life. Fortunately, however, one need not settle that issue in the present context, since cloning does not produce a person who is qualitatively indistinguishable from the individual who was cloned, for, as is shown by the case of identical twins, two individuals with the same genetic makeup, even when raised within the same family, at the same time, will differ in many respects.

How great are those differences? The result of one study was as follows:

On average, our questionnaires show that the personality traits of identical twins have a 50 percent correlation. The traits of fraternal twins, by contrast, have a correlation of 25 percent, non‐twin siblings a correlation of 11 percent and strangers a correlation of close to zero.

(Bouchard, 1995, 54)

Why is the correlation not higher in the case of identical twins? A common answer is that the environment must play a role, and if that is right, it is also natural to think that it must be one’s experiences within one’s family, during the time that one is maturing, that account for the differences. Judith Rich Harris, however, in her book The Nurture Assumption, develops a very strong argument, based on findings by behavioral geneticists, against the view that one’s family plays a significant role in the type of person one turns out to be, and she then argues that it is one’s peer group that is crucial.

Although Harris makes out a strong case for her view, there is an alternative hypothesis that deserves serious consideration – one suggested by a remark by Steven Pinker in his book, How the Mind Works, where he points out that “the genetic assembly instructions for a mental organ do not specify every connection in the brain as if they were a wiring schematic for a Heathkit radio” (1997, 35). Perhaps identical twins, differ, then, because of differences in the wiring of their brains before birth, due to small, more or less accidental events, within their brains at that time.

In any case, regardless of what theory, or combination of theories, is correct, the crucial point is that the personality traits of an individual and his or her clone should, on average, exhibit no more than a 50 percent correlation; moreover, if one thinks that the environment, as normally understood – that is, postnatally – plays an important role, the correlation presumably will generally be even less, given that an individual and his or her clone will typically be raised at different times, and in generations that may differ substantially as regards basic beliefs and fundamental values.

Accordingly, the present argument, if it is to have any chance, must shift from the claim that a person has a right to absolute uniqueness to an appeal to the very different claim that a person has a right to a genetically unique nature. How does the argument fare when thus reformulated?

An initial point worth noticing is that any appeal to a claimed right to a genetically unique nature poses a difficulty for theists: if there is such a right, why has God created a world where identical twins can arise? Many features of the world, of course, are rather surprising if one thinks our world was created by an omnipotent, omniscient, and morally perfect person, so the theist who appeals to a right to a genetically unique nature may simply reply that the presence of twins is just another facet of the general problem of evil. If, however, as I have argued elsewhere (Tooley and Plantinga 2008, 70–150, and 2019, 51–72), evil provides a strong, evidential argument against the existence of God, that response is not very promising.

How can one approach the question of whether persons have a right to a genetically unique nature? Some writers who reject this claim are content to rest with a burden of proof approach. Here the idea is that although it may be that many people think that being a unique individual in the sense of not being qualitatively identical with anyone else is an important part of what is valuable about being a person, the idea that persons have a right to a genetically unique identity is one that, by contrast, has been introduced only recently. Those who advance the latter claim, therefore, need to offer a reason for thinking it is true.

However, one can also offer positive arguments against the claim. One can appeal, for example, to intuitions that one has upon reflection. Thus, one can consider the case of identical twins, and ask oneself whether, upon reflection, one thinks that it would be prima facie wrong to reproduce if one somehow knew that doing so would result in identical twins. I think it would be surprising if many people felt that this was so.

Another way of approaching the issue is by appealing to some plausible general theory of rights. Thus, for example, I am inclined to think that rights exist where there are serious, self‐regarding interests that deserve to be protected. If some such view is correct, one can then approach the question of whether persons have a right to a genetically unique nature by asking whether there is some serious, self‐regarding interest that would be impaired if one were a clone. An initial reason for thinking that this is not so is that the existence of the person from whom one was cloned does not seem to impinge upon one in the way in which being injured, or being prevented from performing some action that harms no one, do: the existence of the other person might well have no impact at all upon one's life.

A second way of thinking about the question of whether there is a right to a genetically unique nature is to consider a scenario in which individuals with the same genetic makeup are very common indeed, and to consider whether such a world would, for example, be inferior to the present world. Imagine, for example, that it is the year 4004 BC, and God is contemplating creating human beings. He has already considered the idea of letting humans come into being via evolution, but has rejected that on the grounds that a lottery approach in such a vital matter as bringing humans into existence seems inappropriate. He also considered creating an original human pair that were genetically distinct, and who would then give rise to humans who would be genetically quite diverse. Upon reflection, however, that idea also seemed flawed, since the random shuffling and mutation of genes would result in individuals who might be physically impaired, or disposed to unpleasant diseases, such as cancer, that would cause them enormous suffering, and lead to premature deaths. In the end, accordingly, the creator decides upon a genetic constitution that is almost the same for everyone, which will not lead to serious physical handicaps and diseases, and which will allow an individual, who makes wise choices, to grow in body, mind and character. God then creates one person with that genetic makeup – call her Eve – and a second individual – Adam – where their only difference is that Adam has an X chromosome, and a funky Y chromosome, whereas Eve has two X chromosomes. The upshot will then be that any descendent of Adam and Eve will be genetically identical either to Adam or to Eve. That genetic endowment leaves scope, however, for development in different directions, depending upon the choices that individuals freely make.

How would such a world compare with the actual world? One way of thinking about that is by using a variation on an idea introduced by John Rawls in his 1971 book A Theory of Justice. Rawls' suggestion was that a just society would be one that it would be rational to choose if one were choosing a society in which to live behind a veil of ignorance, so that one did not know what position one would occupy in that society, or what one’s abilities would be. Now apply this idea instead to possible worlds, and consider whether, if one were choosing from behind a Rawlsian veil of ignorance, it would be rational to prefer the actual world, or the alternative world just described.

That is not, perhaps, an easy question, but clearly there would be some significant pluses associated with the alternative world. First, unlike the actual world, one would be assured of a genetic makeup that would not give rise to various unwelcome and life‐shortening diseases, or to other debilitating conditions such as depression, schizophrenia, etc. Secondly, inherited traits would be distributed in a completely equitable fashion, so no one would start out, as in the actual world, severely disadvantaged, and facing an enormous uphill battle. Thirdly, aside from the differences between men and women, everyone would be physically the same, so people would differ only with regard to the interests they had chosen to pursue, the beliefs they had formed, and the traits of character they had developed based on choices they had made. There would seem, in short, to be some serious reasons for preferring the alternative world over the actual world.

The third advantage just mentioned points, however, to an obvious practical drawback of the alternative world: knowing who was who would be a rather more difficult matter than in the actual world. However, that problem could be dealt with by variants on the above scenario. One variant, for example, would involve having identity of genetic makeup except with regard to the genes that determine the appearance of one’s face and hair. Then one could identify individuals in the way one typically does in the actual world.

Given that change, the alternative world would not be one where, gender aside, individuals would be identical with respect to genetic makeup. Nevertheless, if this other alternative world would be preferable to the actual world, I think that it still provides an argument against the claim that individuals have a right to a unique genetic makeup. For, first of all, the preferability of this other alternative world strongly suggests that genetic difference, rather than being desirable in itself, is valuable only to the extent that it is needed to facilitate the easy identification of people. Secondly, is it plausible to hold that while genetic uniqueness is crucial, an extremely high degree of genetic similarity would not be troubling? For in the alternative world in question, the degree of genetic similarity between any two individuals would be extraordinarily high. Thirdly, the alternative world is one where the initial structure of one's brain is absolutely the same in all individuals. But, then, can one plausibly hold that genetic uniqueness is morally crucial, while conceding that a world in which individuals do not differ from one another with regard to the initial nature of their brains might be better than the actual world? That seems to me implausible.

The upshot is that I think that the three ways mentioned in which the alternative world would be better than the actual world are good grounds for concluding that, all things considered, the alternative world would be better than the actual world. If so, there is good reason to reject the view that genetic uniqueness is morally significant.