Personally, I have never found this line of thinking particularly compelling. An embryo, as created in IVF, is a ball of about 100 stem cells. It has no heart, no brain, and no circulatory system to speak of. It doesn’t even have a digestive tract. There is little to distinguish it from any other random clump of cells other than its unique DNA and its potential to become a person if implanted in a receptive uterus.
Some people might believe those two facts alone means an embryo already qualifies as a human. But I view implanting the embryo the same way I view having sex; it’s a necessary part of the process of procreation, and you don’t get a baby without it.
I see the appeal of the idea that implantation is required for personhood—as far as I know, the embryo will not activate its developmental program beyond a certain point without it.
But this makes sense for the embryo—without implantation (again, as far as I know) the embryo cannot gain mass. Trying to develop further without implantation would be utterly futile.
I see the dependency of an infant as analogous, though admittedly less extreme. An infant without breast milk or a reasonable substitute will starve, and you will never see the later parts of its developmental program. It would be a mistake to see the infant as only potentially human, and I believe it would be a mistake with the embryo as well.
I believe the example of IVF to be inherently pathological, but I will use it here. An IVF embryo (correct me if I am wrong) has largely the same developmental trajectory whichever woman it is implanted into, provided that the pregnancy is successful. Nearly as much as identical twins normally resemble each other, the infants resulting from implanting an identical pair of embryos into different women would resemble each other. Hence implantation, though essential, does not determine identity in the way that which sperm cell fertilizes an egg determines identity. And I think that continuity of identity is a reasonable basis for assessing human personhood.
Thanks for your reply.
From the linked proposal:
I see the appeal of the idea that implantation is required for personhood—as far as I know, the embryo will not activate its developmental program beyond a certain point without it.
But this makes sense for the embryo—without implantation (again, as far as I know) the embryo cannot gain mass. Trying to develop further without implantation would be utterly futile.
I see the dependency of an infant as analogous, though admittedly less extreme. An infant without breast milk or a reasonable substitute will starve, and you will never see the later parts of its developmental program. It would be a mistake to see the infant as only potentially human, and I believe it would be a mistake with the embryo as well.
I believe the example of IVF to be inherently pathological, but I will use it here. An IVF embryo (correct me if I am wrong) has largely the same developmental trajectory whichever woman it is implanted into, provided that the pregnancy is successful. Nearly as much as identical twins normally resemble each other, the infants resulting from implanting an identical pair of embryos into different women would resemble each other. Hence implantation, though essential, does not determine identity in the way that which sperm cell fertilizes an egg determines identity. And I think that continuity of identity is a reasonable basis for assessing human personhood.