Mr. Potato Head and Philosophy

By Julia Galef

If you listen to the Rationally Speaking podcast, you may remember Massimo and me mentioning the Pop Culture And Philosophy series, which is famous for expounding on everything from The Matrix as a case study in simulated universes, to theological paradoxes raised by Homer Simpson's cravings for a burrito. 

Well, a few weeks ago I saw the excellent Toy Story 3 movie, and my first thought as the credits began to roll (well, unless [sniffle] counts as a thought) was: "Those were some complex musings on personal identity. Somebody should really write a 'Toy Story 3 and Philosophy.’” My second thought was: “Hey, I'm somebody...” And indeed, I am. So here we go:

Toy Story 3 and Philosophy, part I: Mr. Potato Head

Perhaps the most hilariously surreal moment in the movie occurs when Mr. Potato Head disassembles himself. He has been imprisoned in a box, and the one hole in the box is nowhere near large enough for him to squeeze out through. So he pops his plastic eyes, nose, ears, arms and feet out of his potato-body (head?), tossing them through the hole so they land in a heap on the ground outside. And just as you're wondering, “What good did that do him?” each body part stirs itself and they all scurry away. They're traveling as a group, but a group of distinct individuals; each part moves independently, seemingly possessed of a mind of its own.

“Now wait a minute,” you might object. “Just because the various body parts are moving independently of each other, that doesn't necessarily mean they have separate minds. Maybe Mr. Potato Head still has the one mind, which is somehow able to control his body parts from afar.”

Well, Hypothetical-You, that's an excellent point! But it's provably false, even within the fantastical and unspecified logic of the Toy Story universe. If you pay close attention, you'll notice a subtle clue that rebuts your one-mind hypothesis: A few scenes later, the various body parts have embedded themselves into a flour tortilla (it's a long story; just watch the movie, ok?), which serves as an adequate, if floppy, substitute body for them. 

Unfortunately, a passing pigeon takes an interest in the tortilla and pecks at it until it falls apart. One shred of tortilla, containing an eye and an arm, sits up and looks around. Then, with the eye spotting a potential threat approaching, the arm nudges another nearby shred of tortilla (containing a leg) to alert it to the situation. 

Do you see where I'm going with this? The fact that this physical communication between Mr. Potato Head's body parts was necessary reveals that the separate parts aren't being controlled centrally by a single mind. The only conclusion left for us to draw is that each part is controlled by an autonomous mind. Which then raises the question: when Mr. Potato Head's parts are all assembled as per usual in his potato-body, does he have one mind, or does he consist of a complex collaboration between independent minds?

And this is — weirdly, astonishingly — a question that applies to our own minds as well. It's pretty well known that the two hemispheres of a human brain each have different functions, and that they communicate constantly via the corpus callosum which connects them. At first blush, this fact doesn't seem to endanger our belief that we each have a single, distinct mind. But what if you sever contact between the two hemispheres?

This has happened to some people. Called “split-brain patients,” they seem to function normally in most circumstances. But the oddness of their condition manifests when you give a piece of information to only one of their hemispheres, which is then unable to communicate the information to the other hemisphere. How do you do this? By giving the information to only one eye, for example, or to only one hand — sensory inputs from the right eye and hand go only to the left hemisphere, and from the left eye and hand only to the right hemisphere. 

This produces some very striking results, like this one described in Derek Parfit's Reasons and Persons:

One of these people is shown a wide screen, whose left half is red and right half is blue. On each half in a darker shade are the words, 'How many colours do you see?' With both hands the person writes, 'Only one'. The words are now changed to read: 'Which is the only colour that you can see?' With one of his hands the person writes 'Red', with the other he writes 'Blue'.

… Or this one, from Thomas Nagel's “Brain Bisection and the Unity of Consciousness”:

One particularly poignant example of conflict between the hemispheres is as follows. A pipe is placed out of sight in the patient's left hand, and he is then asked to write with his left hand what he was holding. Very laboriously and heavily, the left hand writes the letters P and I. Then suddenly the writing speeds up and becomes lighter, the I is converted to an E, and the word is completed as PENCIL. Evidently the left hemisphere has made a guess based on the appearance of the first two letters, and has interfered, with ipsilatral control. But then the right hemisphere takes over control of the hand again, heavily crosses out the letters ENCIL, and draws a crude picture of a pipe.

And just as with Mr. Potato Head, witnessing our brains' component parts make decisions independently when they are no longer connected raises the question of how exactly we should view them when they are connected. Our intuitive sense that a normal (non split-brain) person has one single mind becomes problematic, because now we know that if we cut the corpus callosum, the person appears to have two minds, operating simultaneously and independently. So did another mind pop into existence when the corpus callosum was cut? And if so, what happened to the original mind — is it now located in the left, the right, or neither hemisphere? The questions raised by this explanation are arguably even more mystifying than the original mystery we were trying to explain.

So the only interpretation which doesn’t seem to suffer from internal contradictions is that the whole idea of distinct, countable minds, no matter how intuitive and self-evident it may seem, is in fact an illusion. And this is the conclusion endorsed by the handful of neuroscience friends I’ve cornered and asked about this, yet it’s so staggeringly counterintuitive that it seems to demand the invention of some new, stronger version of the word "counterintuitive.”

I wish I could comment more intelligently on this conclusion, but so far I haven’t managed to muster anything more coherent than “!!!?!!??!” If you want to read more about the split-brain phenomenon and what we should make of it, I'd recommend Derek Parfit (Reasons and Persons, Part III) and Thomas Nagel ("Brain Bisection and the Unity of Consciousness," in his Mortal Questions). And if you figure it out, come back and explain it to me.

Coming up in Part II: Lots-o-Huggin' Bear and Philosophy.