1. Thomas Nagel The View from Nowhere (New York NY: Oxford University Press, 1986) [hereafter VFN].
2. One of the many ways in which my thought-experiment connects with the philosophy of religion is that it implies that we cannot look for an explanation for the existence of conscious subjects that is defined wholly in terms of neurophysiology or physical processes, like the evolutionary process described by Darwin. Since subjectivity does not supervene on neurophysiology, the explanation for its existence will have to include reference to non-physical entities and processes – something that itself has the property of being conscious, which points, given that this entity would have the extraordinary power of conscious entity to bring new conscious subjects into existence, in the direction of God. For examples of such arguments, see J. P. Moreland Consciousness and the Existence of God (London: Routledge, 2008); Richard Swinburne Is There a God? (New York NY: Oxford University Press, 1996), 69–94; idem ‘Arguments from consciousness and morality’, in idem The Existence of God (Oxford: Clarendon Press, 1979), 152–175; Robert Adams ‘Flavors, colors, and God’, in idem The Virtue of Faith and Other Essays in Philosophical Theology (New York NY: Oxford University Press, 1987), 243–262; J. L. Mackie ‘Arguments from consciousness’, in idem The Miracle of Theism (Oxford: Oxford University Press), 119–132.
3. J. P. Moreland and William Lane Craig Philosophical Foundations for a Christian Worldview (Downers Grove IL: Intervarsity Press, 2003), 238.
4. As Galen Strawson convincingly puts the point: ‘It is very natural for us to think that there is such a thing as the “self” – an inner subject of experience, a mental presence or locus of consciousness that is not the same thing as the human being considered as a whole. The sense of the self arises almost irresistibly from fundamental features of human experience and is no sense a product of “Western” culture, still less a recent product of it, as some have foolishly supposed’; Galen Strawson ‘Introduction’, in idem (ed.) The Self? (Oxford: Blackwell Publishing, 2005), vi.
5. For example, the thesis that any world indistinguishable from ours in terms of physical entities or properties is indistinguishable in terms of non-physical entities or properties seems false; there might be a world physically indistinguishable from ours with ectoplasmic spirits that play the right functional roles to count as minds. This is the ‘problem of extras’. For a discussion of the difficulties in formulating the appropriate supervenience thesis, see Andrew Melnyk ‘Physicalism’, in Stephen Stich & Ted Warfield (ed.) Blackwell Guide to Philosophy of Mind (Oxford: Blackwell Publishing, 2003).
6. As Jaegwon Kim puts the matter: ‘Mind–body supervenience can usefully be thought of as defining minimal physicalism – that is, it is a shared minimum commitment of all positions that are properly called physicalist, though it may not be all that physicalism. As is well known, there are many different ways of formulating a supervenience thesis. For present purposes … [i]t will suffice to understand it as the claim that what happens in our mental life is wholly dependent on, and determined by, what happens with our bodily processes’; Jaegwon Kim Physicalism, or Something Near Enough (Princeton NJ: Princeton University Press, 2005), 13–14.
7. Frank Jackson raised this as a concern for standard statements of the physicalist supervenience thesis. See Frank Jackson From Metaphysics to Ethics: A Defense of Conceptual Analysis (Oxford: Clarendon Press, 1998).
8. Daniel Dennett takes the problem of explaining selves as seriously as any physicalist theorist: ‘People have selves. Do dogs? Do lobsters? If selves are anything at all, then they exist. Now there are selves. There was a time, thousands (or millions, or billions) of years ago, when there were none – at least none on this planet. So there has to be – as a matter of logic – a true story to be told about how there came to be creatures with selves. This story will have to tell – as a matter of logic – about a process (or series of processes) involving the activities or behaviors of things that do not yet have selves – or are not yet selves – but which eventually yield, as a new product, beings that are, or have selves’; Daniel Dennett Consciousness Explained (New York NY: Little, Brown & Co., 1992), 413–414, emphasis added.
9. Geoffrey Madell has written on related but somewhat different problems, and his arguments have, not surprisingly, been different from the argument advanced below. For example, in chapter 4 of Mind and Materialism he states that physicalism is totally unable to give an explanatory account of the subjective character of experience, the what-it-is-like-to-be-ness of conscious subjects, as described by Thomas Nagel. He deploys Frank Jackson's famous argument involving the neuroscientist Mary, responding to counter-arguments to Jackson's argument. See G. Madell Mind and Materialism (Edinburgh: Edinburgh University Press, 1981). This is a related but different problem from the problem of how bodies give rise to conscious subjects, which is the one I consider here. In chapter 5, Madell is concerned with a problem more closely related to the one with which I am concerned here; as he describes it, ‘The problem is most clearly seen in relation to the first person. Thomas Nagel put his finger on it in his paper “Physicalism”. Let us envisage the most complete objective description of the world and everyone in it which it is possible to have, couched in the objective terminology of the physical sciences. However complete we make this description, “there remains one thing I cannot say in this fashion – namely, which of the various persons in the world I am”. No amount of information non-indexically expressed can be equivalent to the first person assertion, “I am G.M.”. How can one accommodate the existence of the first-person perspective in a wholly material world?’; Madell Mind and Materialism, 103. This is a different problem from the problem of whether physicalism can explain, compatible with the supervenience thesis, how it that the body of the first child born to my mother could bring me into existence as a subject of consciousness. While the statement of the problem with which Madell is concerned presupposes the existence of an embodied conscious subject (that, he argues, cannot be picked out by any language that reflects materialistic assumptions), he is not concerned with the specific issue of whether an account of the existence of such subjects can be explained by neurophysiological states. I argue that it is not possible to give such an explanation, and hence that dualism is true. At the end of the day, Madell and I are philosophical allies, but we are waging different battles.
10. The point of specifying these assumptions is to make clear that one can consistently specify a logically possible world containing two planets that resemble each other so closely.
11. Thus, for example, you and your twin experience exactly similar random thermal fluctuations and your bodies respond to those fluctuations in isomorphic and hence qualitatively indistinguishable ways.
12. Since you are presumably billions of light years apart, you could not be exposed to, for example, exactly the same sun. But the sun to which you are exposed is qualitatively indistinguishable from the counterpart sun to which your twin is exposed.
13. While this is unlikely if libertarianism is true, it is possible. In any event, it is important to note that the state of affairs in which two persons always agree in their volitions is not inconsistent with libertarianism.
14. This thought-experiment seems to pose no dilemma for reductive physicalism. The eliminativist, for example, denies that ordinary folk categories referring to phenomenal experience, including the phenomenal element of being a subject, have any referent. If this is right, then this thought-experiment does no damage whatsoever to eliminativism.
15. None of this should be taken to imply that minds and bodies cannot causally interact. They undoubtedly do; my visual experience is surely caused by the neurophysiological state of my brain. It is simply to assert that my being the particular subject I am cannot be explained just in terms of neurophysiology.
16. By ‘global’ here, I mean to pick out the most general supervenience theses, applying to all objects, properties, etc. in the universe, rather than the more narrow one focusing on minds.
17. If not, then the relevant global supervenience thesis will have to be supplemented by other theses; however, these other theses will obviously be fully compatible with the basic intuition that everything is ultimately physical.
18. The conditional holds in one direction only. I might be indifferent as between strawberry and chocolate ice cream although they differ qualitatively.
19. My intuition is that the modality is conceptual. It seems reasonable to think that, as a conceptual matter, a physical object X is A's body if and only if A is the subject associated with X. That is, it is part of the very concept of some physical object X being A's body that A is the subject associated with X. It should be noted that the dualist intuition that a subject A could, so to speak, inhabit some other body than the one A actually inhabits is consistent with this conceptual claim. Let A be a subject, X be A's body, and Y be some body distinct from X. The relevant dualist claim, then, is that it is possible that X is not A's body and that Y is A's body. This is consistent with it being necessarily true that A is the subject of A's body; for the claim is just that it is not necessarily true that X (which is, in fact, A's body) is A's body.
20. Another example is the sentence ‘if square circles exist, they are unlike any other objects in the universe’. The statement is not just trivially true in the sense that the antecedent is necessarily false; if the antecedent were true, square circles would disprove the law of non-contradiction and hence be remarkable objects.
21. I am grateful to David Chalmers for this concern.
22. I am grateful to Jaegwon Kim, David Chalmers, Jennifer Corns, David Pereplyotchik, Stephen Layman, Patrick McDonald, and Rebekah Rice for their attempt to help me with an argument that they did not find compelling.