PERSONAL IDENTITY & ETHICS SHOEMAKER
The point is rather that theories of personal identity figure into assessing the arguments/replies.
Accordingly, which claim one should accept on the matters of applied ethics sometimes depends on
which theory (or sort of theory) of personal identity one adopts.
Argument Against Stem Cell Research
(1)Humans come into existence at the “moment” of conception.
(2) Embryos are humans.
(3) Stemcell research requires destroying (25 day old) embryos.
(4) Killing humans is wrong, all else being equal.
(5)Conducting stemcell research is wrong, all else being equal. 
Embryo: Adam splits into B & C > (iii) Adam doesn’t survive
(1)Humans come into existence at the “moment” (1)Humans come into existence at the “moment”
of conception. [assume] of conception. [assume]
(2) A is a human.  (2) Adam is a human. 
(3) A doesn’t survive twinning. (3) Adam doesn’t survive twinning.
(4) When a human dies, it is a tragedy that (4) When a human dies, it leaves earthly
should be mourned. remains
(5) A’s death is a tragedy that should be (5) Upon twinning, Adam leaves earthly
mourned.  remains 
(6) But Adam’s death is not a tragedy that (6) Upon twinning, Adam doesn’t leave earthly
should be mourned! remains!
(7) Human beings don’t come into existence at (7) Human beings don’t come into existence at
the moment of conception.  the moment of conception.  2
Objector: Assume survival requires identity (no cohabitation) > reject (1) > SCR is ok.
Advocate/Lewis: relies on 4 Dimensionalist Reply > Adam survives as both > SCR is not ok.
Adam (B&C) > B
(1)Killing any entity with a future like ours is wrong, all else equal.
(2)Fetuses have a future like ours.
(3)Killing a fetus is wrong, all else equal.
(1) If an entity X has a future like ours, then it will be identical with some future entity Y, which
is like us. [premise]
(2) If X will be identical with some such Y, then X is mentally connectedcontinuous in the
right way with that Y.
(3) If an entity X has a future like ours, then X is mentally connectedcontinuous in the right
way with that Y.
(4) No fetus is MCC mentally connectedcontinuous in the right way with such a Y—after all
fetuses don’t have the right sorts of mental states.
(5) No fetus has a future like ours.
Objector: assume only mind theory > reject (2)
Advocate: assume body/soul theory
At t1, predementia, let me die. At t2, dementia, want to live. Who to listen to?
They’re the same (body theory)
If there’s identity involved, Person at t2 is identical to Person t1 > listen to t2.
They aren’t the same (mind theory)
shouldn’t let one person choose another person to die, all other things being equal.
But the person at t2 has dementia and may not be competent, in which case those who know her
best should decide her fate
▯no one is closer to person at t2, than the former self, so listen to t1.
▯Parfit: the original person has died in t2, mindsets are diff, they aren’t the same. PERSONAL IDENTITY & ETHICS SHOEMAKER