Some philosophers of mind once thought (and perhaps still think) that the best answer to the question “What is the mind?” is simply “The mind is the nervous system”. In defending this claim, these philosophers sometimes make an analogy between prescientific attempts to answer the question “What is lightning?” and the question of “What is the mind?” Our ancestors once answered the lightning question by saying it was a manifestation of a god’s wrath or something. Modern science tells us, however, that lightning is some kind of electrical discharge. And our ancestors used to answer the question “What is the mind” by saying that the mind was the soul, or some thinking substance detached from the body and brain. So in the same way the identity theorists want to claim that, just as with lightning, the modern scientific answer to the question “What is the mind?” is simply “the nervous system”. What else could it be?
One response to this argument is the idea that the mind is not identical with the nervous system, but rather, with the functioning of the nervous system. This response is designed to answer questions of biological chauvinism e.g. If some entity does not have a human nervous system yet demonstrates intelligent behavior are we to say that it does not have a mind simply because it doesn’t have a nervous system like ours? Thus, the identity thesis seems too restricting.
But does identifying the mind with the function of the nervous system also exclude too much? What if we were to say that the mind is identical to the function of the entire body+brain and not just the nervous system alone? After all, it seems like the “internal milieu” of the body might play a functional role of such importance that it would be problematic to simply identify the mind with the nervous system and not the total system of brain + body e.g. the diffusion of hormones in the blood system seems to play a functional role in mental processes. On this view, the nervous system is simply too entangled with the body for there to be a clear-cut psychological distinction of brain and body. To acknowledge the role of the body in cognition and “what it is like” to be a human animal would be to emphasize an “embodied” perspective. So it seems we have recourse for saying that the mind is not identical to the nervous system, and that it might actually supervene on the total brain-body system given that importance of the bodily milieu for determining what it is like to be human.
But is this the end of the issue? Certainly not. Even thornier problems can be raised with the question of “Is the mind identical to the nervous system?” For me, a critical problem with this question is that it does not distinguish between the unconscious mind and the conscious mind. It seems like the question of identity is different for these two types of minds. Given the importance of the unconscious mind for regulating behavior in response to the registration of homeostatic markers in the bodily milieu, it seems like we would be right to say that the unconscious mind is identical with the functioning of the brain-body system. But what about the conscious mind? It might seem plausible to entertain the hypothesis that the conscious mind is not identical with the functioning of the total brain-body system, but rather, is only identical with the functioning of certain parts of the nervous system, such as those which are involved in the “global broadcasting” and multimodal convergence of information in the higher cortical areas.
On this view, the unconscious mind would be identical to the functionality of the total brain-body system insofar as there isn’t an experiential distinction at this level between experiencing oneself as either being “in the head” or “in the body”. For the unconscious mind, the feeling of being is simply distributed throughout the total brain-body system (and perhaps also into the environment, as per the Extended Mind Thesis and “externalist” theories of perception). But for the conscious mind, there seems to be an experiential component wherein we consciously feel ourselves to exist “inside our heads”, looking out from behind our eyes, and capable of losing ourselves inside a detached mind-space in contemplation, remembrance, and deliberation. For the conscious mind, it seems problematic to identify it strictly with the functioning of the total brain-body system precisely because the conscious mind rarely, if ever, experiences itself as if it were the total brain-body system.
So what’s going on here? It seems like the functionality of certain recently evolved, human specific neural circuits is such that it causes us to consciously experience our conscious mind as if it weren’t constrained by mere physical embodiment. After all, humans report instances wherein they float outside their bodies (in surgery, astral projection, or near death experiences, for example). Moreover, controlled experimental work is capable of inducing wild illusions such as that our conscious feeling of our hand is transported into a rubber hand, or that we experience ourselves as looking at our own backs through clever virtual reality setups. Experimental and clinical work has shown beyond a doubt that the conscious mind is capable of experiencing itself as if it weren’t identical to the brain-body system.
So it seems like if we want to answer the question, “Is the mind identical to the nervous system?” we need to first make a distinction between the unconscious mind and the conscious mind. For the unconscious mind, it seems plausible that it is identical to the functionality of the brain-body system plus certain features of the environment integrated functionally in the right way. For the conscious mind, it seems plausible to suppose that it is identical to the functionality of recently evolved human specific neural structures (that might even develop in ontogeny) that allow for generation of a “virtual” level of experience, wherein the “mind-space” we experience ourselves as inhabiting is not constrained by any actual space, but is itself a virtual construction that is essentially a “functional delusion”. Our brain tricks our conscious mind into thinking that it isn’t identical to the functionality of the nervous system, but this is just a clever delusion. I thus think that Daniel Wegner, Ben Libet, Dan Dennett and other thinkers in the “trick of the brain” tradition are right to postulate that, in some sense, the conscious mind is an brain-generated illusion. But it is a brain-generated illusion that allows us to do things that animals without the illusion are not able to do.