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Arguments from Potential Chapter 3 Arguments from Potential “It can’t be human because it contradicts, factually” I n the preceding chapter the question was whether the mere fact of being an embryo excluded the possibility of being human . Our analysis concluded that since the embryo is alive and since living things can obviously grow (“augment”), the answer was “no.” If embryos possess the structures and engage in the activities necessary and sufficient for self-directed growth, there is no inherent metaphysical contradiction, and embryos could be human. Still, there may be other metaphysical or ontological difficulties. Granted that, theoretically, an embryo could be human, is there something about how, concretely, the embryo grows that precludes it from being human? Could there be something about the specific structures and activities of the embryo that makes it logically (and therefore ontologically ) impossible for it to be a human? Here the question is not whether merely being an embryo makes being human impossible, but whether being an embryo of this sort makes it impossible. 77 78 Arguments from Potential Potential and Individuality This very question arises in Donceel’s discussion of whether the embryo is a “virtual” human being. Unlike a heart cell, for example, that possesses all of the genetic material necessary to produce a human being but never does, an embryo possesses not only genetic material but also potential to develop into a being that is recognizably human. This “unique potential” would be the same as the “augmentative power” discussed in the previous chapter and is sufficient grounds, it is argued, to conclude to the presence of a human soul. Donceel concedes that the embryo is different in this respect from other cells, but argues that the biological facts speak against the conclusion that a human is present. As Donceel understands it, prior to the formation of the blastocyst (approximately five days following sperm-egg fusion), the cells that form the embryo are in a state of totipotency; that is, each cell in the embryo is capable of forming a completely new embryo if separated off from the rest.1 This phenomenon, it is presumed, occurs not only in the laboratory but also naturally, as in the case of identical twins. In the latter case, one or more totipotent cells take on their own developmental trajectory and form an organism ontologically distinct from that organism formed by the other totipotent cells. If “potential” is the criterion for personhood, Donceel asks, then it would seem to be the case that each individual totipotent cell is an actual human person: 1. While it does not affect the nature of the argument, modern scientific evidence does not support the claim that totipotency persists until the blastocyst stage. For most mammals, totipotency is preserved only until the two-cell stage (M. Katayama, M. R. Ellersieck, and R. M. Roberts, “Development of Monozygotic Twin Mouse Embryos from the Time of Blastomere Separation at the Two-Cell Stage to Blastocyst,” Biology of Reproduction 82 [2010]: 1237–47). Recent research has been able to take individual cells from a four-cell human embryo and have them continue development separately (cf. H. Van de Velde et al., “The Four Blastomeres of a 4-Cell Stage Human Embryo Are Able to Develop Individually into Blastocysts with Inner Cell Mass and Trophectoderm,” Human Reproduction 23, no. 8 [2008]: 1742–47). However, the fact that a single blastomere can form a structure similar to a blastocyst does not mean it could form all of the needed cell types, let alone the complete body of the organism. In non-human mammals, there is a single report in pigs indicating that full development can be achieved from cells taken as late as the eight-cell stage (S. Saito and H. Niemann, “Effects of Extracellular Matrices and Growth Factors on the Development of Isolated Porcine Blastomeres,” Biology of Reproduction 44 [1991]: 927–36), but even this is well before the formation of the blastocyst. For a detailed discussion of totipotency, see Maureen L. Condic, “Totipotency: What It Is and What It Is Not,” Stem Cells and Development 23 (2014): 796–812. Arguments from Potential 79 The trouble is that, if this is true, every single cell of the zygote, of the morula , or of the blastula, is a human person; for at the earliest stages of embryogeny each cell resulting from the division of the fecundated ovum possesses such a power and virtuality. All these cells are totipotent; each one of them may, if...


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