- The rare condition known as ‘dicephalus1’ occurs when (prior to implantation) a zygote2 fails to divide completely, resulting in twins3 who are conjoined below the neck. Human dicephalic4 twins5 look like a two-headed person, with each brain supporting a distinct mental life.
- Jeff McMahan6 has recently argued that, because they instance two of us but only one animal, dicephalic7 twins8 provide a counter-example to the animalist’s9 claim that each of us is identical with a human animal10.
- To the contrary, I argue that in cases of dicephalus11 it is obvious neither that there is one animal nor that there are two of us. Consequently, the animalist12 criterion does not straightforwardly apply to cases of dicephalus13.
- I conclude by proposing a characterization of dicephalus14 that is both sensitive to the complexity of twinning15 phenomena and not inconsistent with animalism16. On my view, dicephalic17 twins18 are a borderline case of the concept ‘human animal’19.
Sections / Structure
- The Burden of Duplication Objections
- Are (1) and (2) Obviously True?
- 3.1 Alternatives to (2)
- (2') In cases of dicephalus32, there exist (exactly) two subjects of experience.
- (2'') In cases of dicephalus33, there exist (exactly) two minds.
- (2''') In cases of dicephalus34, there exists (exactly) one divided mind.
- 3.2 The Correspondence Intuition
- The presence of human twins35 is sufficient for the presence of two of us.
- 3.3 The Fusion Proposal
- Dicephalus36 as a Borderline Case
- Actually a diversion to reject forensic arguments
Footnote 6: "McMahan (Jeff) - The Ethics of Killing: Problems at the Margins of Life", 2002.
Footnote 23: "Lewis (David) - Survival and Identity", 1976.
Footnote 24: "Nozick (Robert) - Philosophical Explanations", 1981.
Footnote 26: "Johnston (Mark) - Fission and the Facts", 1989.
Footnote 27: "Wilkes (Kathleen) - Real People: Personal Identity Without Thought Experiments", 1988.
Text Colour Conventions (see disclaimer)
- Blue: Text by me; © Theo Todman, 2019
- Mauve: Text by correspondent(s) or other author(s); © the author(s)