The Sleeper Wakes

by Joel Marks

Published in Philosophy Now, Issue No. 89, March/April 2012, p. 52

Now I lay me down to sleep,
I pray the Lord my soul to keep,
If I shall die before I wake,
I pray the Lord my soul to take.

Derek Parfit’s discussion of personal identity in his 1984 book Reasons and Persons is a timeless challenge to our deepest intuitions about who and what we are or even whether we are, that is, exist. Although his treatment of it was novel, the thesis is hardly new. Parfit himself realized its relation to Buddhism, drawing parallels in his last appendix; and in another famous appendix (of his Treatise) Hume dabbled with a similar notion. I have also written about the problem in this column (Issue no. 74) as well as in a science-fiction (or philosophy-fiction) story called “Teleporter on Trial” published in SciFiDimensions.

            My own intuition has been quite clear to me but also perplexing, and in both senses of the latter. Thus, suppose you enter a presumed teleporter and are beamed to Mars. In what seems to me the most likely scenario, only the information about you will be transmitted, since sending an electromagnetic signal is far more efficient and swift that transporting your entire body. So on Mars a brand new body, and in particular brain, will be shaped according to the blueprint of that information; and out of the transmission receiver will walk a person who is in every respect identical to the one who walked into the transmitter on Earth, including in his own mind. The person will believe he or she is you, no doubt about it.

            My feeling, however, is that he or she is not you at all but only an exact replica. I won’t repeat all of the arguments but only say why this is perplexing in two ways. First, it is puzzling: This is because we are left to wonder what you (or the I or self) could be, such that your existence depends on the existence of your body or brain and not on its blueprint. After all, even the existence of your body and brain is problematic; that is to say, in what sense is your body the same body over time, given that all of its component cells are replaced every number of years? (It is not clear to what degree this is true of the brain, but even here it seems plausible to imagine that we could replace your entire brain, cell by cell, if the technology were available to do so, while leaving it essentially the same brain.) Second, it is worrisome: This is because the implication is that instead of your having been teleported from Earth to Mars, if we simply disposed of your remaining body on Earth we would in fact be killing you (while bringing a new person into being on Mars).

            I am writing about these things again because all of a sudden I am possessed of a new intuition. It is common to take waking up from deep sleep as the archetype of continuing to exist as oneself. Even though it can seem puzzling that one is still oneself despite an apparent hiatus in consciousness, who would seriously doubt it? Or put it this way: if one did doubt it, then one would be close to doubting the very notion of a continuing self, which is pretty much the same as doubting the existence of the self altogether. For it hardly conforms to our conception of being so-and-so that we exist only for a single day (unless one is a mayfly).

Indeed, if one doubts that one is the same person upon awakening as the person who went to bed the night before, one could begin to doubt that one is the same person now as the person who began to read this article, and so on to the duration of a mere moment. For what do you really know about your own continuity? Right now you recollect that you have continued in existence since reading “Right now you recollect ….” But would this not also be the case if there were a sequence of selves or “you”s, each of which duplicated the mental content of the one immediately preceding it?

I won’t push that particular line of argument because, Parfit-like, I am more interested in implications for what matters than about the ultimate metaphysics. So return to the sleeping/waking case: There is this gap in consciousness of a clear sense of yourself existing through time, yet upon arising you (in a few moments if not at once) “collect yourself” back (?) into being. Is this really the same you? Up until now I have considered this not only obvious but the most important  fact in the world. One very real application would be as I related in my phi-fi story about teleporters: Any time a person entered one of these contraptions, he would be about to die.

But now for the first time I question that, or anyway that it matters. Instead of entering the teleporter, just put your head down on your pillow tonight. Tomorrow morning someone will awaken on that pillow, believing he or she is you. No one else will have a clue that there might be anything different either. I now ponder and wonder and marvel: What else could matter? Whatever the metaphysics of the situation, if these empirical facts are the case, then could anyone, including the person who went to bed the night before, complain of some loss? Suddenly I am at a loss … to see what has been lost.

Joel Marks is Professor Emeritus of Philosophy at the University of New Haven and a Bioethics Center Scholar at Yale University. He would like to thank Chris Bateman of International Hobo for re-sparking his interest in Parfit, and acknowledge the aid of Thomas Metzinger’s The Ego Tunnel (Basic Books, 2009) in further cutting the cord to himself.