An Open Peer Commentary to appear in the American Journal of Bioethics. Not for distribution or quotation. 1 Skepticism About the “Convertibility” of Induced Pluripotent Stem Cells

In this issue’s target article, Stier and Schoene-Siefert purport to ‘depotentialize ’ the argument from potentiality based on their claim that any human cell may be “converted ” into a morally significant entity, and consequently, the argument from potentiality finally succumbs to a reductio ad absurdum. I aim to convey two reasons for skepticism about the innocuousness of the notion of cell convertibility, and hence, the cogency of their argument. First, some brief remarks about potential. Following Aristotle, Stier and Schoene-Siefert distinguish two types of potential, “active ” and “passive. ” This distinction has been captured elsewhere in terms of two senses, producing or becoming (Buckle 1988). An entity is said to have potential in the sense of becoming if it maintains its identity through a developmental process; it must persist, despite state changes, while developing new features and qualities. What matters is that the entity possesses some causal power, or potency, such that under suitable conditions it will develop into another entity. By contrast, potentiality in the sense of production does not require preservation of identit