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Conjoined twinning & biological individuation

Boyle, Alexandria ORCID: 0000-0001-8827-5479 (2020) Conjoined twinning & biological individuation. Philosophical Studies, 177 (8). 2395 - 2415. ISSN 0031-8116

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Identification Number: 10.1007/s11098-019-01316-x


In dicephalus conjoined twinning, it appears that two heads share a body; in cephalopagus, it appears that two bodies share a head. How many human animals are present in these cases? One answer is that there are two in both cases—conjoined twins are precisely that, conjoined twins. Another is that the number of humans corresponds to the number of bodies—so there is one in dicephalus and two in cephalopagus. I show that both of these answers are incorrect. Prominent accounts of biological individuation, which treat the organism as an integrated whole, reveal that in these and other cases of conjoined twinning the ‘twins’ share a single human animal. This has a number of consequences for the debate about what we are. First, if animalism is true, individuals of our kind can be—and are—profoundly psychologically divided. Second, cephalopagus twinning does not divide animalism from its rivals, as has been claimed. Finally, animalists can reply to a vicious species of the ‘too many thinkers’ problem to which they are allegedly uniquely vulnerable.

Item Type: Article
Official URL:
Additional Information: © 2019 The Author
Divisions: LSE
Subjects: B Philosophy. Psychology. Religion > B Philosophy (General)
Date Deposited: 08 Sep 2022 14:18
Last Modified: 23 Jun 2024 23:27

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