  One response to this line of argument has been to claim that embryos possess a kind of potential that somatic cells and HESCs lack. An embryo has potential in the sense of having an “active disposition” and “intrinsic power” to develop into a mature human being (Lee &amp; George 2006). An embryo can mature on its own in the absence of interference with its development. A somatic cell, on the other hand, does not have the inherent capacity or disposition to grow into a mature human being. However, some question whether this distinction is viable, especially in the HESC research context. While it is true that somatic cells can realize their potential only with the assistance of outside interventions, an embryo’s development also requires that numerous conditions external to it are satisfied. In the case of embryos that are naturally conceived, they must implant, receive nourishment, and avoid exposure to dangerous substances in utero. In the case of spare embryos created through in vitro fertilization—which are presently the source of HESCs for research—the embryos must be thawed and transferred to a willing woman’s uterus. Given the role that external factors—including  technological interventions—play in an embryo’s realizing its potential, one can question whether there is a morally relevant distinction between an embryo’s and somatic cell’s potential and thus raise doubts about potentiality as a foundation for the right to life (Devolder &amp; Harris 2007).