Sleeping in the Ship of Theseus

The ship wherein Theseus and the youth of Athens returned [from Crete] had thirty oars, and was preserved by the Athenians down even to the time of Demetrius Phalereus, for they took away the old planks as they decayed, putting in new and stronger timber in their place, insomuch that this ship became a standing example among the philosophers, for the logical question of things that grow; one side holding that the ship remained the same, and the other contending that it was not the same. —Plutarch, Theseus

This is an old philosophical question: if I take a thing and replace every bit of it piece-by-piece with new parts does it remain the same thing? In the case of a boat, the question isn't particularly important, though it is somewhat interesting. But--assuming consciousness and the sense of I stem entirely from the functioning of the human brain--when one considers a person or a brain, the stakes are a bit higher.

When I applied to UChicago those many years ago, one of the essays I chose to write was on the topic of teleportation. It was a philosophical prompt:

In a book entitled The Mind’s I, by Douglas Hofstadter, philosopher Daniel C. Dennett posed the following problem: Suppose you are an astronaut stranded on Mars whose spaceship has broken down beyond repair. In your disabled craft there is a Teleclone Mark IV teleporter that can swiftly and painlessly dismantle your body, producing a molecule-by-molecule blueprint to be beamed to Earth. There, a Teleclone receiver stocked with the requisite atoms will produce, from the beamed instructions, you—complete with all your memories, thoughts, feelings, and opinions. If you activate the Teleclone Mark IV, which astronaut are you—the one dismantled on Mars or the one produced from a blueprint on Earth? Suppose further that an improved Teleclone Mark V is developed that can obtain its blueprint without destroying the original. Are you then two astronauts at once? If not, which one are you?

I don't know what I wrote (hey, when you look this good, you don't have to know anything) but I do remember that this question has always boiled down to one thing for me: continuity of consciousness. Of course, this question is merely a high tech reformulation of the question posed by the Ship of Theseus. We're breaking down a person and rebuilding them somewhere else from something else. The problem is again the same when one considers the possibility of mind-uploading in the future--if I transfer my consciousness into a machine, is it still me?

This question is important because before I teleport or transfer my mind to a machine I'd like to be sure that I'm not simply killing myself and letting a duplicate--granted, one who has all of my memories and the distinct sense of being me--take my place. One way of asking this question might be: is the transition from this mode of experience to the next one (i.e. this body to the new one, or this body to the machine) smooth? Or do I experience a discontinuity in my conscious experience?

If we compare these seminal events (teleportation or mind-uploading) to everyday experience, the difference seems stark. But in part this assumes a static present that is illusory. Our bodies are, like the Ship of Theseus, in constant flux, undergoing a constant give-and-take with our environment. Like the Ship, over time our bodies are slowly replaced with new parts as molecules and nutrients freely flow in and out. And yet this is not scary because I seem to experience continuity of consciousness. My body may be made of entirely different materials than it was a decade ago but there haven't seemed to be any sudden, sharp breaks in my sense of I. My consciousness has carried on smoothly over this period, even as my body was being replaced.

But let's delve a bit deeper. If I were experiencing discontinuities in consciousness, if my consciousness were dying and a different but equivalent one were taking its place (say, every hour), how would I know it? The sense of a conscious self that I'm experiencing at this moment would be less than an hour old, yet it would share all of the memories of its predecessors, since the information contained in the hardware of my brain (i.e. memories) is still there to be accessed at will. I would then die within the hour--my lifetime limited to the brief period between discontinuities in consciousness--only to be replaced by someone else.

I'll illustrate why I say this discontinuity is equivalent to death with an example from Star Trek: The Next Generation. The transporters in Star Trek seem to operate according to the same principle as Dennett's thought experiment above: the body is destroyed on the transporting pad, the information of how to build a person is relayed to the destination, and a new version of the person is reconstructed from local materials. In an episode called "Second Chances" we (and the crew of the Enterprise) discover that years earlier a transporter mishap had led to two materializations: one Will Riker was beamed back to his ship, another rematerialized at the transport point after the original transporting-Riker's body was destroyed. The result was that two copies of Riker after the time of that botched transport exist: Will Riker and Tom Riker. They may be "the same person" in almost every technical sense but ultimately, since they clearly have distinct conscious experiences, they cannot really be the same person. Thus there cannot be a smooth transition of conscious experience from before-transport to after-transport and, I suspect, when the body is destroyed during the transport process, the "original" person dies and consciousness ends. Both Tom and Will #2 are recreated at their destinations but that's little comfort to the original transporter (Will #1) as his conscious experience in this universe has come to an end.

Now I mused earlier about the possibility of such a discontinuity happening naturally every hour or so. Clearly there's no reason to think this is the case, though I don't think we can rule it out. But what about every day? We experience a discontinuity of consciousness every single night when we fall asleep. Is it possible that in the interregnum between sleeping and waking--in the trough between dreams--our consciousness dies and a new one is born? Every time we awaken our minds would literally be born anew. We believe we are the guy who went to sleep the night before when in fact he is effectively dead, replaced by a new consciousness (confusingly, us). Sleep, then, is equivalent to the transport or mind-uploading process in that we experience a discontinuity of conciousness that signals the death of the original and the creation of the replacement.

Is this even remotely possible? I have no idea. But for a time last night I was afraid of sleep. So seize the day--it may be the only one you ever experience.