Examining the links between today’s ideas of radical life extension and age-old notions of immortality   From Plato’s notion of generation to Derrida’s concept of survival to such modern phenomena as anti-aging treatments, cryogenics, cloning, and whole-brain uploads, Adam Rosenthal’s Prosthetic Immortalities shows how the dream of indefinite life has always been a technological one: a matter of prosthesis. He argues that every biological instance of perpetual life, from one-celled organisms to rejuvenating jellyfish to Henrietta Lacks’s “immortal” cancer cells, always results in the transformation of the original being. There can, therefore, be no certainty of immortality. Yet, because finite mortal life is already marked by difference, division, and change, as Rosenthal concludes: “the problem of immortality will not cease to haunt us.”   Prosthetic Immortalities examines the persistence of humans’ aspirations of deathlessness, showing that the link between immortalization and prostheticization is not unique to a single period but is, rather, a ubiquitous element of the discourse of immortality, encompassing both modern technoscientific efforts and religious discourses of an afterlife. Rosenthal asks to what extent the emergence of a virtual, posited, immortal presence follows from the tenets of empirical science—and not simply from the discourse of biology but also, and more radically still, from biological organization itself.   Rosenthal ultimately argues that the discovery of biological immortals—lifeforms that naturally have indefinitely long lifespans, such as cancer cells and bacteria—present novel conceptual difficulties for traditional philosophical approaches to mortality and selfhood, asking whether it is life itself that first births immortalizing prostheses.