<< And on a Peter Singer related note: wouldn't it take substantially longer
than 28 days for lots of disabilities to show themselves? What's he trying
to do with that 28 day thing, anyway?
>>
28 days hasn't to do with disabilities but with personhood--it applies to everyone. The idea is that it takes several months for a baby to develop enough cognitive capacity to take anything like an interest in its future--probably three months. But he suggests that instead of drawing the line (for all babies) at three months, and risk killing some fast developrs, we draw the line at one month--it's rough and ready, but, he surmises, early enough so that even if most babies don't atatin personhood for several months later, we'd be safe enough for utilitarian purposes if we sid that we deem anyone 29 days old to be a proper person.
Singer thinks that we could ethically kill any baby, disabled or not, before the 28 day limit, at least as ethically as we could kill any nonperson. We could also ethically kill anypne older than that who never rose to, or permanently fell below, the cognitive development of a baby that yound. The issue arises with severely disabled babies in aprticular because, from a utilitarian point of view, they are (a) lesss likely than normal babies to lead happy lives, (b) more of a burden on their parents and a cost to society,a nd (c) replaceable. So from a util pov, if they would be replaced, he thinks, would be more happiness, and so they should be killed and replaced.
I don't endorse thsi argument. I just explain it.
--jks