Solidarity after nature: From biopolitics to cosmopolitics.

What is sustaining the divide between nature and nurture, even though sciences like epigenetics have been challenging it for at least two decades? Evelyn Fox Keller asked this question and considered it a logical problem rooted in terminological confusion within the sciences. In this article, we propose a complementary diagnosis of the problem: the nature-nurture divide is (re-)mobilized when society faces questions of inclusion and solidarity. With examples stemming from the fields of insurance and health care, immigration policy and epigenetics, we demonstrate how the nature-nurture divide is performed through techniques of classification for a politics of solidarity. We identify a common to these different examples that we coin 'biopolitical imputation'. We use this term to draw attention to how (Western) societal institutions, including science, create solvable problems out of complex situations, defining human actors and their agency along the lines of the nature-nurture divide as a guide. We argue that the tenacity of the nature-nurture divide is therefore not only a logical problem needing better scientific concepts, but also a cosmopolitical problem asking for a more profound reflection on the ontology and ethics of solidarity in order to move beyond the biopolitics of nature versus nurture.