Consider the two following cases:
Fission – Your right cerebral hemisphere and your left cerebral hemisphere are simultaneously and separately transplanted into the empty skulls of your two identical triplet siblings. The rest of your body is destroyed. Each hemisphere functions normally with both siblings are endowed with normal cognitive functions.
Replication – Your entire body is scanned by a machine which records all the information about the type and location of its molecules. The machine uses this information to construct two replicas of you. Your body is entirely vaporized in the process.
In his recent article “Personal Identity, Substantial Change and the Significance of Becoming”, the philosopher Michael Otsuka asks whether it is rational for you to anticipate and to grant significance to the experiences of your two siblings in the Fission Case while denying that it is rational in the Replication Case. Otsuka argues for a positive answer on the basis of a criterion of “substantial change”. In the Fission Case, you become each of two other persons, while in the Replication Case, you are merely replaced by two other persons. Arguably, in the Fission Case, there is a substantial change in your identity because two streams of consciousness are brought into existence instead of one before the transplantation. There is however a “substance-connection” that makes it rational for you – before the transplantation – to care about the experiences that your two siblings will have after the transplantation. In the Replication Case, no such substance-connection prevails and therefore it may be argued that what will happen to the replicas is rationally irrelevant for you.
Otsuka contrasts his account with other views of about personal identity, especially Parfit’s reductionist account. According to Parfit, psychological continuity and connectedness are the relevant criteria to employ when asking “what matters” in the prudential sense. On these criteria, Fission and Replication should be dealt with in the same way: assuming that your two replicas have memories of your past experiences, especially those just preceding the vaporization of your body, you should care about their experiences almost as much as about yours. The divergence between Otsuka’s substance account and Parfit’s substance account lies in the fact that the former is grounded in an ontology of things while the latter depends on an ontology of events and processes. Which one is the most convincing is of course a question difficult to answer but it seems that most of us – as Otsuka suggests – will not regard the Fission Case and the Replication Case as perfectly symmetric. This provides a reason – not necessarily a decisive one, though – to favor Otsuka’s view.
Consider however a third case:
Downloading – Your stream of consciousness is uploaded and stored in a non-biological hardware and almost instantly downloaded in a new biological brain placed inside a human body with no direct genetic relatedness with your original body. Your original body is destroyed. You have intact memory of your experiences before the upload and downloading operations.
This case is a standard science-fiction one and is for instance the one that Netflix’s series Altered Carbon uses in its narrative plot (though in the series the main character’s stream of consciousness is “reactivated” 250 years after having been uploaded). By assumption, psychological continuity and connectedness are satisfied and hence an account like Parfit’s would treat this case in the same way as the two preceding ones. What about Otsuka’s? This probably depends on what is taken as the appropriate view of the mind-body problem. On the dominant, materialist and functionalist views, there is probably a case to consider that there is some form of substance connection between your previous and current selves. After all, considering that consciousness is the result of functional operations whose realization is independent of the “hardware” on which they are “running” (in the sense that they could be realized with a different hardware), it may be argued that the appropriate sort of connection prevails. Consider however
Multiple Downloading – Your stream of consciousness is uploaded and stored in a non-biological hardware and almost instantly downloaded in a new biological brain placed inside a human body with no direct genetic relatedness with your original body. Your original body is destroyed. You have intact memory of your experiences before the upload and downloading operations. Due to a mistake, the operation has been done twice, with two non-genetically related bodies.
Multiple Downloading is qualitatively similar with Replica, except for the fact that in the former the two selves that result from the operation have a body that is genetically unrelated to yours. This difference can only reinforce Otsuka’s conclusion that you should not care about the two new selves’ experiences. I regard this result as counterintuitive as it is not clear why and how a mistake leading to duplicate your stream of consciousness should be prudentially relevant. There is no obvious reason for treating Downloading and Multiple Downloading differently. Someone rejecting the functionalist view in the mind-body problem may still argue that in Downloading the appropriate connection between the two selves do not prevail. One may then deny that the future selves’ experiences are prudentially relevant in both Downloading and Multiple Downloading. This is consistent with the ontology of things that Otsuka is defending. This conclusion still strikes me as counterintuitive but this is probably due to my functionalist leanings!