“A self, it seems, is not all or nothing but the sort of thing that there can be more of or less of. When, in the process of a zygote’s cellular self-multiplication, does a person start to exist? Or when does a person, descending into dementia or coma, cease to be? There is no simple answer—it is a matter of degrees.”

— Larissa MacFarquhar, How to be Good (The New Yorker, September 5, 2011)