If I clone myself what relation does the clone have to me? And what does this tell me about what makes me – me? My clone is not my self. It will be different in personality, cognition, as well as its place in space-time. This difference can help us to assert, away from the materialistic picture of identity, that we are not simply our genes. This should impact our moral and social thinking about the dangers of cloning, which remain troublesome, writes Kathinka Evers.

Ever since Ian Wilmut’s team of British embryologists cloned a sheep called Dolly in 1997, there has been a heated debate amongst scientists, politicians and the general public about whether or not cloning should be allowed. One of the most frequently expressed worries, in particular to the possibility of cloning human beings, is that it would produce “xerox copies” of living organisms - identical creatures. Fearfully, one envisions an army of indistinguishable individuals: homo xerox. Yet what this means, and the nature of these cloned “identities”, is often left unspecified.

This concern is based on a misunderstanding of the type of identity-relation which cloning involves: It is based on the false belief that cloning produces individuals that are totally identical, physically as well as mentally. The fear of armies of identical individuals will seem unreal and lose its power once the true nature of cloning has been understood.

From a philosophical point of view, the assumption that cloning would produce “identical individuals” is not immediately intelligible because the concept “identity” is ambiguous.  

A classical philosophical distinction differentiates numerical identity (the relation of that object to all others) from qualitative identity (based on the qualities of the object). An old query is whether qualitative identity entails numerical identity: can objects which have all their properties in common be numerically distinct? Are qualitatively identical (‘indiscernible’) objects numerically identical? And are numerically identical objects also indiscernible?

The fear of armies of identical individuals will seem unreal and lose its power once the true nature of cloning has been understood.

Leibniz raised both these questions, and answered them with ‘Leibniz’ s Law’. Really this is two laws, two logical principles of identity, which can be described as follows:[

Firstly, the identity of indiscernibles: if x and y are identical they have all their properties in common. In a formulation without plural terms: whatever is true of A is true of whatever is identical to A.  Let’s call this qualitative identity “indiscernibility” and use it to look at cloning. The proposition under analysis is: P - A clone is an organism that is identical to another organism.

Notice firstly that two organisms are mentioned in P, ruling out numerical identity. So P must be asserting the indiscernibility of clones. But “indiscernibility” in what sense? By Leibniz’s Law it is not possible for two things to differ numerically only, there must be a qualitative distinction between them. Distinct objects must have some feature which the other does not possess, by virtue of which they are distinct. Accordingly, clones cannot be strictly indiscernible.

Nor are they. Clones are living organisms occupying a unique place in space and time. Their lives form unique spatio-temporal sequences, and by virtue thereof every clone has a part of its identity which nothing else can possibly share. The belief that clones are indiscernible must consequently be given a more modest interpretation.