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Against Branching Identity


Would you survive if your consciousness branched into two or more streams? Commonly discussed within the context of split-brain scenarios, this possibility might soon become commonplace with mind uploading technology. Cerullo (Minds and Machines, 25, 17–36, 2015) suggests that after nondestructive mind uploading and other branching scenarios, personal identity would continue in two streams of consciousness. Thus he argues for what he calls branching identity. In this discussion, I evaluate the theory of branching identity and Cerullo’s arguments for it, concluding that branching identity is insufficiently justified and does not yield a better interpretation of branching cases than provided by Parfit (1984).

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  1. For example, the Brain Preservation Foundation ( is dedicated to studying and promoting such possibilities.

  2. Locke (1994), in his Essay (Book II, Ch. XXVII), argues that insofar as a later state of consciousness remembers an earlier state of consciousness, the two states are part of one consciousness. Parfit (1984: 205-206, 219-223) summarizes various problems with memory as the sole criterion of identity, and therefore he holds that memory is just one part of Relation R.

  3. Another way to put this point employs awareness versus the information of which you are aware (Graziano 2013: 13): the awareness is a capacity directed at information (from the senses, from the sub-consciousness, etc.), but the information will determine, to a large degree, what the awareness attends to and how it feels to have that awareness. Additionally, consider the distinction between phenomenal-consciousness and access-consciousness (Block 1995). Although a person can have one without the other (Block 1995: 233), it seems that one’s phenomenal-consciousness (the ‘what it’s like’ aspect of consciousness) is fleshed out and has a particular feel owing at least partly to the states one can and does access (access-consciousness).

  4. There is no identity problem if just one half of the brain survives and carries forward consciousness since that half would carry one’s identity.

  5. Split-brain cases can be modified to closely mirror uploading cases—e.g. Parfit (1984: 254-255) imagines his two brain halves with equal content being placed in duplicate bodies.

  6. See Figure 1 in Pinto, et al. (2017: 1232) for a useful contrast between the traditional view and the cited paper’s new findings.

  7. Pinto, et al. (2017: 1232) cite Corballis and Trudel (1993), Corballis (1995), Corballis and Corballis (2001), Savazzi and Marzi (2004), and Savazzi et al. (2007).

  8. Pinto, et al. (2017: 1236) encourage further investigation of the dwindling group of split-brain patients.

  9. Lewis (1976) discusses this possibility, and Parfit (1984: 258) recognizes it.

  10. The phrase “equally ourselves” is ambiguous: equal qualitatively, numerically, or somehow else?

  11. Demarest (2016: 580-581) expresses ambivalence about the non-branching axiom, although she tentatively accepts that two branches of you are non-identical owing to branching simpliciter. Also, she makes two main claims about the relation between branching and contradictory properties: (i) that one person can have contradictory properties (support: self-visitation), and (ii) “that branching is sufficient for non-identity, even if there are no contradictory properties” (support: a case where A splits into B and C but B immediately travels to a past era, so B and C live their lives completely separately) (Demarest 2016: 570). The latter case doesn’t necessarily support my critique of Cerullo’s theory of branching identity, since Demarest’s concern (as when she states “branching is sufficient for non-identity”) is numerical identity.

  12. A person’s consciousness is unified, roughly, if the person has internal access to all of his or her representational states. In claiming ‘internal access’, I’m setting aside the extended mind thesis (Clark and Chalmers 1998), which may do a lot more damage to our sense of identity than branching, for it entails that individuals have mental states in notebooks and other external devices.

  13. Cerullo (2015: 30) briefly notes the possibility of more than two branches.


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I am grateful to an anonymous reviewer for insightful comments and questions.

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Correspondence to William A. Bauer.

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Bauer, W.A. Against Branching Identity. Philosophia 45, 1709–1719 (2017).

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  • Branching identity
  • Non-branching axiom
  • Personal identity
  • Consciousness
  • Mind uploading
  • Relation R