Key Arguments

• He notes that if we treat the four options as different real possibilities, 'the case is a problem for us too', just as it is for the Cartesian; but 'On the Reductionist View, the problem disappears.'
• Reductionism holds that the four claims 'do not describe different possibilities, any of which might be true, and one of which must be true. These claims are merely different descriptions of the same outcome.'
• He specifies the outcome completely: 'There will be two future people, each of whom will have the body of one of my brothers, and will be fully psychologically continuous with me, because he has half of my brain. Knowing this, we know everything.'
• From this perspective, the further question 'But shall I be one of these two people, or the other, or neither?' is deemed 'an empty question.'
• He offers an analogy: the 1881 split of the French Socialist Party, where given certain details it becomes an 'empty question' whether the original party ceased to exist or continued as one of the two successors, because we can fully describe what happened without resolving that identity question.
• He then distinguishes two kinds of empty questions: (a) those with no answer where any answer would be arbitrary (e.g. 'Shall I survive?' in central Combined Spectrum cases), and (b) those where the question gives 'different descriptions of the same outcome', and one description may be better though nothing substantive turns on choosing it.
• My Division is of the second kind: there is in a sense an 'answer' (a best description), but the facts are completely fixed independently of that answer.
• He claims that in this case, 'The best description is that neither of the resulting people will be me.', though he immediately adds that the more important issue is not which description is best but what ought to matter prudentially—whether division is like death or like survival.

Source Quotes

For Cartesians, this case is a problem with no possible solution. Suppose that, for the reasons given earlier, we reject the claim that each of us is really a Cartesian Ego. And we reject the claim that a person is any other kind of separately existing entity, apart from his brain and body, and various mental and physical events. How then should we answer the question about what happens when I divide? I distinguished four possibilities.

If we believe that these are different possibilities, any of which might be what happens, the case is a problem for us too. On the Reductionist View, the problem disappears. On this view, the claims that I have discussed do not describe different possibilities, any of which might be true, and one of which must be true. These claims are merely different descriptions of the same outcome. We know what this outcome is.

We know what this outcome is. There will be two future people, each of whom will have the body of one of my brothers, and will be fully psychologically continuous with me, because he has half of my brain. Knowing this, we know everything. I may ask, ‘But shall I be one of these two people, or the other, or neither?’

Knowing this, we know everything. I may ask, ‘But shall I be one of these two people, or the other, or neither?’ But I should regard this as an empty question. Here is a similar question.

Here is a similar question. In 1881 the French Socialist Party split. What happened? Did the French Socialist Party cease to exist, or did it continue to exist as one or other of the two new Parties? Given certain further details, this would be an empty question. Even if we have no answer to this question, we could know just what happened.

About some questions we should claim both that they are empty, and that they have no answers. We could decide to give these questions answers. But it might be true that any possible answer would be arbitrary. If this is so, it would be pointless and might be misleading to give such an answer.

In such a case this question has, in a sense, an answer. The question is empty because it does not describe different possibilities, any of which might be true, and one of which must be true. The question merely gives us different descriptions of the same outcome. We could know the full truth about this outcome without choosing one of these descriptions.

Since this is so, we can claim that this description is the answer to this question. And I claim that there is a best description of the case where I divide. The best description is that neither of the resulting people will be me. Since this case does not involve different possibilities, the important question is not, ‘Which is the best description?’

Since this case does not involve different possibilities, the important question is not, ‘Which is the best description?’ The important question is: ‘What ought to matter to me? How ought I to regard the prospect of division? Should I regard it as like death, or as like survival?’ When we have answered this question, we can decide whether I have given the best description.

Key Concepts

• Suppose that, for the reasons given earlier, we reject the claim that each of us is really a Cartesian Ego. And we reject the claim that a person is any other kind of separately existing entity, apart from his brain and body, and various mental and physical events. How then should we answer the question about what happens when I divide?
• On the Reductionist View, the problem disappears. On this view, the claims that I have discussed do not describe different possibilities, any of which might be true, and one of which must be true. These claims are merely different descriptions of the same outcome.
• There will be two future people, each of whom will have the body of one of my brothers, and will be fully psychologically continuous with me, because he has half of my brain. Knowing this, we know everything.
• I may ask, ‘But shall I be one of these two people, or the other, or neither?’ But I should regard this as an empty question.
• In 1881 the French Socialist Party split. What happened? Did the French Socialist Party cease to exist, or did it continue to exist as one or other of the two new Parties? Given certain further details, this would be an empty question.
• We could decide to give these questions answers. But it might be true that any possible answer would be arbitrary.
• The question is empty because it does not describe different possibilities, any of which might be true, and one of which must be true. The question merely gives us different descriptions of the same outcome.
• And I claim that there is a best description of the case where I divide. The best description is that neither of the resulting people will be me.
• The important question is: ‘What ought to matter to me? How ought I to regard the prospect of division? Should I regard it as like death, or as like survival?’

Context

Second half of this excerpt, where Parfit states how a Reductionist should understand the division case, introduces a general distinction between two types of 'empty' identity questions, and proposes that My Division is best described as involving no survival of him, shifting attention to the prudential question of what matters.