We spend our entire lives trying to figure out how to deal with consciousness. For this reason, the problem of consciousness is one of the most important and most interesting philosophical and scientific problems. The problem is staring us in the face at every moment: it’s simultaneously banal and incredibly profound. Unlike most scientific questions, however, there is a very intuitive sense that the problem of consciousness isn’t simply one that we will solve with more science. It feels like it’s not a contingent fact that we can’t explain the emergence of consciousness from the physical. On the other hand, as philosophy teaches us, intuitions are not to be accepted uncritically.
It’s hard to pinpoint exactly what it is that’s so troubling about consciousness as compared to other vexing issues like, say, the ongoing search for a theory of quantum gravity or a cure for cancer. Perhaps it’s this: it seems so arbitrary that consciousness would arise from a given brain state. Science is a reductive business: biology reduces to chemistry, which reduces to physics. At least in principle, we can derive biological laws from physical laws. When we observe a biological phenomenon, we can explain it in terms of chemistry, and once we’ve done so, there seems to be nothing left to explain. We can see that the underlying chemistry simply must produce the biology, and the underlying physics the chemistry; it seems logically inevitable that it must be so; inconceivable and incoherent to imagine otherwise. But consciousness doesn’t appear to fit. We can correlate physical states with mental states, but we can’t find any reasons why the mental should emerge from the physical. It seems entirely conceivable that the brain states that produce the conscious experience of typing this essay would produce the experience of climbing Kilimanjaro, or else that it should provide no conscious experience at all.
There are few brute facts in the world, and as scientifically minded people we learn to distrust them. To say that something is a brute fact is to admit that there can be no further explanation. It’s an admission of defeat. It hurts the ego and it frustrates our natural sense of curiosity. But there must be brute facts, or at least a single brute fact. The logical argument goes as follows: there is no set that contains all sets. If we let reality stand for all that exists—a definition necessary to encompass theories of multiverses and the like—then it’s clear that, since reality can’t possibly be a set that contains all sets, there must be some possible realities that don’t exist. And therefore, it must be a brute fact that this reality and not any of the others exist—no possible mechanism from within reality can explain the meta-question of “why this reality and not some other reality?” We can always keep asking, whatever multiverse theory you come up with, why not this other multiverse theory?
The problem is that these brute facts, as far as we know, concern the most fundamental pieces of reality. The macro-structure of the universe emerges from its micro-structure. It’s not a brute fact that the Earth exists: that fact can be explained by a series of progressively lower-layer and more fundamental facts, until you reduce the Earth’s existence to a very complicated series of applications of the brute laws—the laws that can’t be explained in terms of anything more fundamental, but simply are, and that’s all there is to it—that govern the smallest pieces of matter and the smallest packages of energy. Brain states can be reduced in the same way. But we can’t explain why a given brain state gives rise to a given subjective state, and it seems conceivable and logically possible that the same brain state would give rise to another subjective state or no subjective state at all, in a way it isn’t conceivable that a given slice of physics would give rise to different chemistry. Maybe it’s simply a brute fact that a functional configuration equivalent to a given brain state gives rise to a given subjective experience, but this seems surprising and unsatisfactory as an explanation.
The philosophical zombie argument is intuitively very persuasive. It says that it’s logically possible that a copy of a human being—someone or something that shares every physical attribute with a human, including an exact copy of the human’s brain state—would lack consciousness. There certainly seems to be no contradiction in imagining someone who looks like us, talks like us, who in every way behaves like us and whose every physical measurement is identical to ours, but who experiences no subjective states, someone that there is nothing “it is like to be.” And if that is so, there’s something missing in a physical, reductionist or epiphenomenalist take on consciousness. (A take that says that ultimately, consciousness can be explained in purely physical terms.) But again, this is a thorny, complicated issue where intuitions may be faulty and lead us astray.
Here’s another thing that seems to be conceivable: that there exist facts or theories so complicated and so alien to normal human thought patterns that although they’re true, no human brain could comprehend them. And maybe the explanation for consciousness is one such theory. After all, we’re not so different from dumb apes, and our continued survival as a species in no way hinges on our understanding of how it is that we are conscious, so there’s no reason to suggest that we must have evolved brains capable of understanding themselves completely.
This might not seem like such a problem to me if I were willing to reject the idea that all that exists is physical, or supervenes or emerges from the physical and is ultimately reducible to it. That all true scientific theories that don’t reduce to physics are only different ways to look at problems that could in principle be reduced to physics. If only I’d adopt some kind of Cartesian dualism. But this is doubly unsatisfactory. For one thing, there is no evidence that anything nonphysical is going on in the brain, and we would expect that it would be detectable if a nonphysical consciousness or soul causally influenced the brain. For another, this explains nothing and seems ultimately no more satisfying as an explanation than the brute fact sort of physicalism. If there is a mysterious, nonphysical mind-substance that provides consciousness, we’re left trying to explain how that works. And if it’s a brute fact that it works, that seems no less mysterious than the brute fact that certain functional brain states give rise to certain subjective states.
There’s no evidence that the universe is anything more than matter and energy. I’m open to the idea that physics could detect something that doesn’t fall under those broad categories, but it seems to me that whatever future physics finds, it won’t be fundamentally different from matter and energy in any way that bears on the question of consciousness. We’re left with trying to understand how certain configurations of physical fields, energies and substances—whatever their final makeup turns out to be—can give rise to consciousness.
It doesn’t matter whether or not you believe in a god or gods. Even if you think that a personal god created the universe with the express intent of creating conscious humans, you can still wonder exactly what mechanism God chose for creating consciousness. There’s nothing inherent in theism that calls for dualism. You can be a religious monist, and the same questions will still haunt you.
Nov 21, 2011