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How Many Organisms during a Pregnancy?

Published online by Cambridge University Press:  01 January 2022


Mammalian placental pregnancy is a neglected problem case for theories of organismality. This example is closer to home than those typically discussed within philosophy of biology. I apply evolutionary and immunological accounts of organismality to the “counting question”: How many organisms are present during a placental pregnancy? I conclude that an evolutionary approach yields the answer two, because of bottlenecking, germ-soma sequestration, and sexual recombination. By contrast, an immunological approach answers one, because of pervasive interactions across the placenta. This analysis expands and refines recent work on a biologically informed metaphysics of pregnancy, an undertheorized area of philosophy of science.

Biological Sciences and Medicine
Copyright © The Philosophy of Science Association

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I thank members of the BUMP project group—Teresa Baron, Suki Finn, Alex Geddes, Elselijn Kingma, Anne Sophie Meincke, and Ziggy Schilpzand—for very helpful comments on versions of this manuscript. I also thank participants and audiences at symposia on the Metaphysics of Pregnancy at the BSPS conference 2018 in Oxford and the PSA conference 2018 in Seattle and at the Sowerby Philosophy and Medicine Colloquium, KCL, November 2018. This article is part of a project, Better Understanding the Metaphysics of Pregnancy, that has received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program, under grant 679586.


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