"It is a deep truth that all of a person's life [i.e., over time] is as much his life. If we are impressed by this truth—by the unity of each life—the boundaries between lives will seem to be deeper. This supports the claim that, in the moral calculus, these boundaries cannot be crossed. On the [Empty Individual] View, we are less impressed by this truth. We regard the unity of each life as, in its nature, less deep, and as a matter of degree. We may therefore think the boundaries between lives to be less like those between, say, the squares on a chess-board, dividing what is all pure white from what is all jet black. We may think these boundaries to be more like those between different countries they may then seem less morally important [...] If some unity is less deep, so is the corresponding disunity. The fact that we live different lives is the fact that we are not the same person. If the fact of personal identity is less deep, so is the fact of non-identity. There are not two different facts here, one of which is less deep on the [Extreme Separatist] View, while the other remains as deep. There is merely one fact, and this fact's denial. The separateness of persons is the denial that we are all the same person. If the fact of personal identity is less deep, so is this fact's denial."