"Any entity which, remaining the same individual, will develop into a paradigmatic instance of a substantial kind already is an instance of that kind. The one-cell human organism originating with the substantial change which occurs upon the penetration of a human ovum by a human sperm typically develops, as one and the same individual, into a paradigmatic instance of the rational bodily person, the human person; in every such case, therefore, it is already an actual instance of the human person."Making the argument about my own one-cell zygote (call it "Z"), it goes like this--
- Z developed into a paradigm case of a human person, i.e. JK, the person writing this post.
- Z is the same individual as JK, not a different individual.
- Personhood is a substantial (or essential) kind, not an accidental kind - it's a property that an individual can't gain or lose while remaining the very same individual. THEREFORE,
- Z was a person.
Why not think personhood is just as accidental as butterflyhood? A butterfly would no doubt be appalled by the suggestion that she -- she -- was once a lowly crawling caterpillar. I'm not sure there's anything more backing up the essentialness of personhood than the human equivalent of butterfly-pride.