Chapter 1st of the book. This chapter explores the fundamental ambiguity of the concept of plasticity – between openness and determination, change and stabilization of forms. This pluralism of meanings is used to unpack different instantiations of corporeal plasticity across various epochs, starting from ancient and early modern medicine, particularly humouralism. A genealogical approach displaces the notion that plasticity is a unitary phenomenon, coming in the abstract, and illuminates the unequal distribution of different forms of plasticities across social, gender, and (...) ethnic groups. Taking a longer view of the plastic body as a ubiquitous belief in traditions predating and coexisting with modern medicine will help contextualize the seeming radicalism of today’s turn to permeability and the exceptionalism of Western findings. By highlighting the complex biopolitical usages of plasticity in the past, the chapter warns against simplistic appropriations of the term in contemporary body/world configurations driven by findings in neuroscience, epigenetics and microbiomics. (shrink)