Fission, First Person Thought, and Subject-body Dualism

In “The Argument for Subject Body Dualism from Transtemporal Identity Defended” (PPR 2013), Martine Nida-Rümelin (NR) responded to my (PPR 2013) criticism of her (2010) argument for subject-body dualism. The crucial premise of her (2010) argument was that there is a factual difference between the claims that in a fission case the original person is identical with one, or the other, of the successors. I argued that, on the three most plausible interpretations of ‘factual difference’, the argument fails. NR responds that I missed the intended, fourth interpretation, and that, in any case, with an additional assumption, the argument on the third interpretation goes through. I argue that the fourth interpretation, while insufficient as stated, reveals an assumption that provides an independent argument, namely, that in first person thought about future properties we have a positive conception of the self that rules out having empirical criteria of transtemporal identity. I argue that the considerations offered for this thesis fail to establish it, and that we do not bring ourselves under any positive conception in first person thought. I argue also that on the third interpretation, the first premise of the argument is inconsistent with the necessity of identity.