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foundation of common, “lived” experience – I lay down to sleep, then I wake up, and I, upon self-
reflection, sense no difference in my person. Dreamless sleepers remain human persons, despite their
dreamless sleep. The only reasonable assumption we can make is that substantial being cannot come
and go as purely subjective experiences, else we damage the concept of personhood entirely. 98 This
insight makes possible the presence of personal being in the human zygote well before the awakening of
personal subjectivity. 99
It seems to be that the zygote and the adult human body are the same living being, differing
merely at the stage of development. This appears to justify believing the zygote a human person. 100
Crosby notes a possible objection, an ironically Aristotelian objection: how can we argue for the
personhood of a single zygote, which may divide into two separate bodies through a process called
twinning? Crosby, as devil’s advocate, argues that this instability in the zygote threatens the
incommunicability of personhood – incommunicability referring to the absolute and unrepeatable value
of a particular human being as a human person. 101 Incommunicability arises from the stability of a
particular person, insomuch as a particular person is itself without any confusion to possibly being
someone else. Is not the zygote, with this understanding in mind, unsuitable to be considered a discrete,
personal body, since it retains a high potential for divisibility? 102 In other words, only with a greater
individuality – a stronger claim that this body (zygote) is a particular person’s body – does the zygote
itself become “matter capable of being informed by a personal soul.” 103
John Crosby responds that even adult human beings “lag behind the person with respect to
indivisibility.” 104 For example, siamese twins may appear to share a body, he argues, but we
nevertheless intuit their discrete personhood. 105 The fact that human bodies can be genetically copied
does not interfere with personhood, because a person is more than a mere body. Persons live through
their bodies and through their minds. The issue here appears to be more an issue of ensoulment than an
issue of personhood, and this ensoulment issue has, at most, partial bearing on the issue of personhood.
The ensoulment problem changes no asp