7. Why the skeptic needs to presuppose that the copy would care

This takes us back to the “resolve and follow through” strategy of section 4, where the original subject resolves beforehand to trust his memory should he appear to wake up on Mars. Should this strategy work as planned, the person who wakes up on Mars—original or copy—would follow through on the resolve, and we get the situation just described, where the original subject, should he awaken, would always divine his identity correctly, whereas the person waking up on Mars would get it right only half the time (and the copy would always get it wrong).

The successful execution of this strategy, in other words, would be practical proof of the point of logic of the previous section: just because the person who awakens on Mars will not know whether he is real or copy, and thus whether the machine had worked or failed, doesn’t mean that the original subject, should he so awaken, would not know either.

The skeptic, as explained in section 4, would contend that this strategy could never be executed in practice because the original subject, should he awaken on Mars, would wake up in two minds, conflicted as to whether he was real or copy, and would thus be unwilling, lest he prove to be the copy, to follow through on his resolve. He’d effectively be mute on the question. I pointed out then that this protest rests on the presupposition that the copy, should he awaken on Mars, would care to know that the machine had failed, in the same way that the original subject, should he awaken on Mars, would care to know that the machine had worked. That is to say, for the original subject to wake up in two minds, conflicted and mute, the copy would have to care. But notice now also that the claim that the original subject would wake up in two minds, conflicted and mute, is essentially the conclusion that the skeptic was driving at all along, viz., that the original subject would not know upon waking whether he was real or copy. It’s a strongish version of that conclusion, since you can be ignorant about something without being in two minds, or conflicted/mute about it—as when someone is wrongly certain about something. Nevertheless, it is essentially the trumpeted skeptical conclusion: when the skeptic claims that the original subject would not know upon waking whether he was real or copy, he’s essentially thinking of someone in two minds, conflicted and mute. We were trying to pin down the skeptic’s argument for that conclusion and it should now be evident that the conclusion rests on the presupposition that the copy would care.

In all of this, therefore, the fact that the skeptic tends to conceive of the original subject’s ignorance in a specific way—as a form of reticence grounded in mental conflict, or uncertainty—is critical. The skeptic needs the ignorance to take this form, not only to block the “resolve and follow through” strategy, but also to be able to justify his claim that the original subject would be ignorant of his identity in the first place. As we saw, the mere fact that waking up as the original subject is exactly like waking up as the copy does not entail that the original subject would be ignorant of his identity upon waking. But if we introduce the presupposition that the copy would care, then the conclusion in question would follow, since the original subject, should he awaken, would now wake up conflicted/mute over his identity; a fortiori ignorant of his identity. He doesn’t need to be conflicted/mute over his identity to be ignorant of his identity, but it seems to me that the skeptic’s contention that he would be ignorant rests on the claim that he would be thus conflicted and mute, which rests in turn on the presupposition that the copy would care.

Formally, the presupposition, and attendant mental conflict/reticence, serves to “plug the gap” in the inferential non sequitur discussed in the previous section. It would now follow, from the fact that the person who wakes up on Mars would be ignorant of his identity, that the original subject, should he wake up on Mars, would be ignorant of his identity as well. This would not in general follow, but if we assume that the ignorance in question is of the conflicted/mute form, then it would follow. In terms of the divine tests, the presupposition that the copy would care ensures that the person who wakes up on Mars (original or copy) would be conflicted/mute in every test in God’s series, undecided on who he was; a fortiori, conflicted in every test in which he happened to be the original subject.

Note that there is no issue, this time, over the validity of our inference:

The person who wakes up on Mars is conflicted and mute.

The person who wakes up on Mars is the original subject.

Ergo: The original subject is conflicted and mute.

because being mentally conflicted and mute is not a modal property of an individual, but a bare factual one. Whether an individual is conflicted and mute does not depend on how that individual is characterized in the way that whether an individual knows something may well be.

As advertised previously, then, the combination of these two:
yields the desired skeptical conclusion:
with the presupposition also serving, on the side, to block the original subject from executing the “resolve and follow through” strategy.

This is the essential shape of the skeptic’s reasoning, as I see it. And the difficulty with it is that, while the fact cannot be denied, the presupposition is not necessarily true—something which is easy to miss, because it’s easy to miss, to begin with, that the presupposition needs to be there. In a case where the presupposition is not true, as in the one imagined previously, the skeptic can still show that the person who wakes up on Mars will be ignorant of his identity, but he will no longer have an argument that the original subject, should he awaken on Mars, would be so ignorant. The door would be open for the original subject to execute the “resolve and follow through” strategy: should the machine work, he’d find himself waking up on Mars and, following through on his resolve to trust his memory, would be bound to judge correctly that he was the one who entered the machine and that the machine must therefore have worked. What remains is the question—a full discussion of which was promised previously, and to which an affirmative answer has been presupposed so far—of whether, in such a case, the original subject would thereby know that the machine had worked. Would his correct judgement in a case like this amount to knowledge?