Yesterday morning around dawn I sat hypnotized by “Paradise Falls”. I had hiked there from my parents’ house while my family slept, as I often do when we visit my parents.
Although at first it didn’t feel that way, I wonder if I have been harmed by philosophy. I gazed at the waterfall, thinking about Boltzmann brains – thinking, that is, about the possibility that I had no past, or a past radically unlike what I usually suppose it to be, instead having just then randomly congealed by freak chance from disorganized matter. On some ways of thinking about cosmology, there are many more randomly congealed brains, or randomly congealed brains-plus-local-pieces-of-environment, than there are intelligent beings who have arisen in what we think of as the normal way, from billions of years of evolution in a large, stable environment. If such a cosmology is true, then it might be much more likely that I have randomly congealed than that I have lived a full forty-five years in human form. The thought troubled me, but also the spark of doubt felt comfortable in a way. I am accustomed to skeptical roads.
Of course, most cosmologists flee from the Boltzmann brains hypothesis. If a cosmology implies that you are very likely a Boltzmann brain, that’s normally taken to be a reductio ad absurdum of that cosmology. But as I sat there thinking, I wondered if such dismissals arose more from fear of skepticism than from sound reasoning. I am no expert cosmologist, with a view very likely to be true about the origin and nature of the universe or multiverse and thus about the number of Boltzmann brains vs. evolved consciousnesses in existence – but neither are any professional cosmologists sufficiently expert to claim secure knowledge of these matters, the field is so uncertain and changing. As I gazed around Paradise Falls, the Boltzmann brain hypothesis started to seem impossible to assess. This seemed especially so to me given the limited tools at hand – not even an internet connection! – though I wondered whether having such tools would really help after all. Still, the world did not dissolve around me, as I suppose it must around most spontaneously congealed brains. So as I endured, I came to feel more justified in my preferred opinion that I am not a Boltzmann brain. However, I also had to admit the possibility that my seeming to have endured over the sixty seconds of contemplating these issues was itself the false memory of a just-congealed Boltzmann brain. My skepticism renewed itself, though somehow this second time only as a shadow, without the force of genuine doubt.
I considered the possibility that I was a computer program in a simulated environment. If consciousness can arise in programmed silicon chips, then presumably there’s something it’s like to be such a computerized consciousness. Maybe such computer consciousnesses sometimes seem to dwell in natural environments, fed with simulated visual inputs (for example of waterfalls), simulated tactile inputs (for example of sitting on a stone), and false memories (for example of having hiked to the waterfall that morning). If Nick Bostrom is right, there might be many more such simulated beings than naturally evolved human beings.
I considered Dan Dennett’s argument against skepticism: Throw a skeptic a coin, Dennett says, and “in a second or two of hefting, scratching, ringing, tasting, and just plain looking at how the sun glints on its surface, the skeptic will consume more information than a Cray supercomputer can organize in a year” (1991, p. 6). Our experience, he says, has an informational wealth that cannot realistically be achieved by computational imitation. In graduate school, I had found this argument tempting. But it seemed to me yesterday that my vision of the waterfall was not as high fidelity as that, and could easily be reproduced on a computer. I fingered the mud at my feet. The complexity of tactile sensation did not seem to me the sort of thing beyond the capacity of a computer artificially to supply, if we suppose a future of computers advanced enough to host consciousness. We are so eager to reject skepticism that we satisfy ourselves too quickly with weak arguments against it.
Now maybe John Searle is right, and no computer could ever host consciousness. Or maybe, though computer consciousness is possible, it is never actually achieved, or achieved only so rarely that the vast majority of conscious beings are organically evolved beings of the sort I usually consider myself to be. But I hardly felt sure of these possibilities.
The philosophers who most prominently acknowledge the possibility that they are simulated beings instantiated by computer programs don’t seem very worried by it. They don’t push it in skeptical directions. Nick Bostrom seems to think it likely that if we are in a simulation, it is a large stable one. David Chalmers emphasizes that if we are in a simulation scenario like that depicted in the movie The Matrix, skepticism needn’t follow. And maybe it is the case that the easiest and most common way to create an artificial consciousness is to evolve it up through a billion or a million years in a stable environment; and maybe the easiest, cheapest way to create seeming conversation partners is to give those seeming conversation partners real consciousness themselves, rather than making them Eliza-like shells of simple response patterns. But on the other hand, if I take the simulation possibility seriously, then I feel compelled to take seriously also the possibility that my memories are mostly false, that I am instantiated within a smallish environment of short duration, perhaps inside a child’s game. I am the citizen to be surprised when Godzilla comes through; I am the victim to be rescued by the child’s swashbuckling hero; I am the hero himself, born new and not yet apprised of my magic. Nor did I have, at that moment, a clever conversation partner to convince me of her existence. I might be Adam entirely alone.
Fred Dretske and Alvin Goldman say that as long as my beliefs have been reliably enough caused by my environment, by virtue of well-functioning perceptual and memory systems, then I know that there’s a real waterfall there, I know that I have hiked the two kilometers from my parents’ house. But this seems to be a merely conditional comfort. If my beliefs have been reliably enough caused…. But have they? And I was no longer sure I believed, in any case. What is it, to believe? I still would have bet on the existence of my parents’ house – what else could I do, since skepticism offers no advice? – but my feeling of doubtless confidence had evaporated. Had everything dissolved around me at that moment, though I would have been surprised, I would not have felt utter shock. I was not seamlessly sure that the world as I knew it existed beyond the ridge.
I turned to hike back, and as I began to mount the slope, I considered Descartes’s madman. In his Meditations on First Philosophy, Descartes seems to say that it would be madness seriously to consider the possibility that one is merely a madman, like those who believe they are kings when they are paupers or who believe their heads are made of glass. But why is it madness to consider this? Or maybe it is madness, but then, since I am now in fact considering it, should that count as evidence that I am mad? Am I a philosopher who works at U.C. Riverside, whom some readers take seriously, or am I indeed just a madman lost in weird skepticism, with merely confused and stupid thoughts? Somehow, this skepticism felt less pleasantly meditative than my earlier reflections.
I returned home. That afternoon, in philosophical conversation I told my father that I thought he did probably exist other than as a figment of my mind. It seemed the wrong thing to say. I wanted to jettison my remnants of skepticism and fully join the human community. I felt isolated and ridiculous. Fortunately, my wife then called me in for a round of living-room theater, and playing the fox to my daughter's gingerbread girl cured me of my mood.
I thought about writing up this confession of my thoughts. I thought about whether readers would relate to it or see me only as possessed for a day by foolish, laughable doubts. Sextus Empiricus was wrong; I have not found that skepticism leads to equanimity.