- At least since Parfit 1984, there have been connections drawn between puzzle cases about personal identity, on the one hand, and normative questions, on the other. The relevant cases are hypothetical cases involving apparent fission1 of one person into multiple people (through separation of brain hemispheres, teletransportation2 accidents, and so on), fusion of multiple people into one, slow changes in one organism that yields a different person at the start than at the end, and suchlike. Questions that arise include the following. What is the practically rational thing to do, from the standpoint of a person facing the prospect of splitting into two people? Should the products of such fission be held morally responsible for the actions of their progenitors? How does fission bear on special duties created by family ties, friendships, and personal debts?
- However, we think reflection on puzzle cases from the personal identity literature impacts on moral theorising in another important way. To date, much of the focus has been on potential consequences for moral and practical questions focused on obligations or duties of people in particular personal relationships: how should I think about my future welfare how might my obligations differ between my friends and family and their qualitative clones, how should we distribute moral rewards and punishments, praise and blame, given that intuitively these should go to the same person who performed the relevant earlier actions. (See, for instance, Williams 1981, Unger 1992, Jeske 1993, Eklund 2004, and Shoemaker 2007.)
- We claim that the metaphysics of identity also has implications for impersonal moral requirements: that is, obligations to people regardless of whether they happen to share a particular connection with the agent. We aim to show that on one popular account of what is going on in cases of fission, fusion3 etc., put together with two popular normative accounts of what (or who) matters for moral action and how what matters should be aggregated, yields what seems to be an unacceptable moral reductio. While we discuss ways of responding to this clash in the final section of this paper, the cases we consider raise the prospect that, given one of the common stances in the metaphysics of personal identity, some common (plausible, frequently defended) fundamental normative commitments are not jointly tenable, and stand in need of revision.
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