From Physicalism To Mysterianism

 In a previous post on this blog, I defended a broadly physicalist approach to the mind-body problem. Arguments from causal closure and scientific explanation led me to the think that the mind, like many other aspects of our “manifest image”, should be identified with physical phenomena on a posteriori grounds. 

Recently, I’ve come to think that this view is mistaken for an unexpected reason: It seems to me that we are not in a position to make any confident claims about whether the mind is or is not physical. To the extent that the question of mind-body identity can be meaningfully posed at all, I now lean towards a form of mysterianism. Here is a brief outline of my reasons:

A compelling way to frame the mind body problem is in terms of what has been called the “explanatory gap”. This highlights the intuitive sense in which, even if all the physical facts are explained, we’ll still be no closer to understanding how the physical “stuff” yields our technicolor phenomenal experiences. Why are those brain states like *this*!? Someone might ask. 

In one sense, the explanatory gap may seem to depend upon a confusion. Namely, identities aren’t really the sorts of things that can be explained at all. There’s no explanation for why I’m me or why Clark Kent is Superman. In each case, it’s the same person. If explanations ever come to an end, surely it must be with identity. Likewise, if we have good reasons for thinking that the mind is identical with the brain, we don’t require any further explanation for why they are, in fact identical. 

But the anti-physicalist has a more pressing version of this problem available to them: In normal cases of scientific identification, it seems possible to deduce all higher-order physical truths from the actual set of microphysical truths. To use a simple example, if I know all the facts about H20, it seems clear that I will be in a position to deduce all the facts about water on the basis of those truths. We know that water is whatever liquidy stuff plays the “water” role in our environment, so once we know that that role is filled by H20, we’ll know everything we need to know about water, right? If that’s the case, it seems like the obvious impossibility of deducing such truths about consciousness is good evidence against physicalism.

One of the most popular (and plausible, in my opinion) physicalist replies to this claim comes from what has been called “a posteriori physicalism”. According to a posteriori physicalism, microphysical truths alone do not put us in a position to deduce higher-order physical truths, even in humdrum cases such as water and H20. The key mistake that they point out is the assumption that we know, a priori, that water is the liquidy stuff that plays the water role in our environment. While this might seem completely obvious, keep in mind that what matters is whether that claim is a priori, not whether it is obvious. 

Upon reflection, we can easily imagine cases in which that obvious fact turns out to be false. For instance, we could discover that water isn’t actually liquid at all and that we are being deceived by technologically advanced aliens about its nature. In such a case, knowing that H20 is a liquidy stuff wouldn’t be enough to know anything about water because water isn’t a liquidy stuff at all! We discovered, a posteriori, that it was very different than what we initially supposed. As far fetched as this may seem, this case and many others like it cannot be ruled out on a priori grounds. Consequently, we cannot deduce all physical truths, a priori, from microphysical truths alone.

However, while this reply may succeed as a reply to the a priori physicalist, it fails to address what I’ve come to think is a much deeper divide between the mind and other physical phenomena.

Consider any physical phenomena of the everyday world. Water, heat, plants, and anything else that science appears to explain. In normal cases, when we identify something like water with an empirical concept from a more developed theory such as H20, we are effectively concluding that truths about one of the identified terms (water) are systematically correlated with truths about the other term (Complex structures of H20 molecules). Even if we don’t make the exact same judgements about each, what matters is that judgements about one can be, in principle, replaced by judgements about the other (or some disjunctive set of such judgements). 

It doesn’t matter if we never reach a level of sophistication where this is actually possible. What matters is that, in ordinary cases, a necessary condition for a posteriori identity is the *in principle* dispensability of the higher-order theoretical vocabulary. In other words, it must be possible to replace our talk about water with talk about H20 without missing out on any significant truths about reality (excluding, of course, trivial cases such as the fact that we use the term “water”). Just like we can capture all the truths about the world by talking about Clark Kent alone, rather than Clark Kent and Superman, we should be able to talk about H20 instead of water and still say everything we said before. If they’re really the same thing, this much seems to me to be obvious. 

In light of the above considerations, we now have a new necessary conditions for a posteriori identification that can replace that of the a priori physicalist: If some empirical phenomenon X is identical with some empirical phenomenon Y, the vocabulary associated with “X” must be, in principle, capable of being replaced by the vocabulary associated with “Y” without any loss of expressive power with respect to the coarse grained empirical facts those terms were used to describe. (For a more sophisticated development of ideas along these lines, see Sellars 1965)

Now, if this condition is necessary for a posteriori identification, how does the mind fare? With respect to phenomenal consciousness, there is one simple reason why I believe this condition can never be satisfied: Unlike our ordinary empirical concepts, our sensory experiences do not merely serve to describe reality. They also play an essential epistemic role in justifying our empirical beliefs. Even if I am mistaken about what I perceive, I am always in a privileged epistemic position with respect to what seems to be the case. It is because we have such experiences that we can be in a position to form judgements about the world at all. Most importantly, such experiences put us in a position to form judgements about the brain. 

Because our judgements about the brain depend upon the epistemic function of our sensory experiences, we can never be in a position to replace judgements about phenomenal consciousness with judgements about brain states. Why not? Because judgements about brain states are empirical judgements. As such, they require us to recognize what we experience as what we experience in order for us to have justified beliefs about them at all. If we abandoned the vocabulary of conscious experience, we would undermine the very basis for identifying the mind with the brain in the first place. Since abandoning our mental vocabulary is self-refuting, we cannot be in a position to identify the mind with the brain. 

Does this conclusion entail anti-physicalism? Not quite. Recall the reason why the mind cannot be identified with the brain. It had nothing to do with the metaphysical nature of consciousness. Rather, the impossibility derived from the epistemic role that consciousness plays. This epistemic role, however, carries no implications for what the nature of consciousness actually is. On the contrary, because it plays an essential epistemic role for our empirical knowledge, our inability to identify consciousness with anything physical derives from factors that have nothing to do with what consciousness actually is. Whether consciousness is physical or non-physical, we are not in a position to identify it as such. And since this inability does not stem from the metaphysical nature of consciousness, it does not allow us to draw any metaphysical conclusions about consciousness for or against physicalism. In short, the epistemic role played by sensory consciousness prevents us from being in a position to reach any firm conclusion about whether it is a physical phenomenon. 

Taken alone, this thesis yields a novel form of mysterianism that appeals to the epistemic features of consciousness, rather than the conceptual limitations of our current scientific framework. I believe there is a further question to ask about whether this leaves any meaningful way to formulate the mind body problem at all, but for now I’ll end at that.