Why Materialism Collapses Into Panpsychism
Weak materialism is the thesis that mental properties are aspects of entities (states, events) that also have physical properties, as with token identity theories. Strong materialism is the thesis that mental properties are physical properties, as with type identity theories. The physical properties are typically taken to be properties of the brain, specifically neurophysiological properties. It is not generally supposed that mental properties are instantiated outside the brain—so the materialism is taken to be a brain-centered materialism. The materialist doesn’t tend to think that mental properties are instantiated in the world at large simply because they are instantiated in the brain; the materialist is not a panpsychist. But it is difficult to see how materialism can avoid sliding into panpsychism because of the following question: why are brain properties so special that only they are accompanied by mental properties? What restricts the mental to the cerebral, given that the brain is just a physical object like others? If physical properties are co-instantiated with mental properties in the brain, why aren’t they also co-instantiated with them elsewhere? Shouldn’t nature be uniform in this respect? Suppose some Martian scientists, composed of exotic material unknown to us and without brains like ours, were to visit earth and investigate terrestrial brains, discovering that they house mental properties as well as physical. Wouldn’t it be a reasonable induction on their part to infer that other matter on earth must also be correlated with mental properties? After all, there is nothing special about the matter of the brain—it is just complexes of molecules—so we would expect that matter in general would show the same correlations. If mind supervenes on matter in the brain, why shouldn’t it supervene on matter in other locations? There is nothing unique about matter in the brain—that is the whole point of materialism—so matter should exemplify mind everywhere. To be more specific, if it is electrical activity in the brain that is key to the existence of mind, then electricity should be associated with mind wherever it exists—which is pretty much everywhere. Hence materialism collapses into panpsychism.
It is true that this seems odd from a human perspective, because we don’t normally suppose that mind exists virtually everywhere—that is not our commonsense conception of the world. We feel it only in ourselves and infer it only for beings similar to us. But consider this analogy: we have discovered that heat is molecular motion, but molecular motion exists almost everywhere, so heat does too, despite that being contrary to what we normally think. Even cold objects have heat in them! Only at absolute zero—a rare state of affairs—does heat disappear. It isn’t that heat exists in boiling water but not in rainwater despite molecular motion in both—that would be contrary to the uniformity of nature—but rather that our common ways of talking are in error. The thermal and the molecular-dynamic are indissolubly connected, contrary to initial appearances (we only feel heat in certain things as a result of the peculiarities of our contingent senses). Similarly, we only feel mind in the case of brains, but since mind is an aspect of matter in brains, it is also an aspect of matter elsewhere—by the uniformity of nature. It isn’t that mind miraculously disappears from matter once matter leaves the confines of the head! That matter came from elsewhere and will go elsewhere, so it had mind in it from the beginning and will go on having it. Another analogy: suppose we discovered that liquid water is H2O but had never thought about ice being water (we have never seen the transition from solid to liquid water); then we discover that ice is also H2O. It would be wrong to declare that not all H2O is water because ice is H2O but not water; rather, we have discovered, contrary to our initial impressions, that water is more widespread than we supposed, existing also in the frozen polar-regions. In the same way the panpsychist maintains that the co-existence of mind and matter in the brain is not an isolated freak of nature; rather, it is a universal fact of nature. If matter can be mind in the brain, then it must be mind elsewhere too. Thus materialism and panpsychism necessarily go together.
This is not a problem for materialism per se; it just turns out that materialism implies that mind is spread more widely than is commonly supposed. It turns out that it is spread as widely as electricity, this being the important physical property in the case of the brain. We already knew that mind has two locations in the human body—the brain in the skull and the enteric nervous system (the “bowel brain”). Not exactly pan- perhaps, but at least bi-: so we should be prepared to accept that the mind is spread even more widely. Nor is this at all inconsistent with materialism: materialism says that the mind is in the matter of the brain; panpsychism says there is mind wherever there is matter. Everywhere that mind is matter is there too, which is the essence of materialism (either weak or strong). Nothing dualistic is implied by panpsychism. It is just that the materialist might be surprised to find himself a proponent of panpsychism—that wasn’t quite what he signed up for. But if you insist that the essence of mind is matter, don’t be surprised if mind turns up everywhere that matter is. The only way out of this is to claim that some kinds of matter are special, capable of producing mind while other matter is mentally inert; but that is to give up on the materialist doctrine—mind is not spooky matter! And don’t start waving your hands about the brain’s complex organization: that is not what the materialist is maintaining, but rather that mental properties are tied to matter as such—not its abstract organization (whatever that is exactly). As some wit once remarked, British Rail is complex and organized too, but it isn’t conscious! No, the materialist may as well acknowledge that panpsychism comes with the territory—just as pan-thermalism does.
What does not imply panpsychism is dualism: if the mind has nothing essentially to do with the brain, then there is no argument showing that it must be found associated with other physical things—for it may exist in isolation from the matter of the brain. Mind could be annexed to other physical things, according to a dualist, and so is not inextricably connected to specific sorts of matter. Nor is it an inevitable accompaniment of matter, or matter of it. Similarly, if heat had nothing to do with molecular motion, there would be no argument showing that heat exists wherever there is molecular motion. So dualism does not imply panpsychism. Nor does a view that asserts the existence of a special mind-producing property in the brain, perhaps unknown, that is not found elsewhere. So long as this property is found only in the brain, there is no slide into panpsychism, since it is not matter as such that is the determining factor. Functionalism could go either way, depending on how it is formulated: if it is just the existence of causal inputs and outputs that matters, we get a similar slide; but if we try to beef it up with something conceptually richer, the answer will depend on how widely that beefed up functional property is distributed (biological function will certainly involve a good deal of spread). If functionalism is taken as a species of materialism, then it will surely tilt in a panpsychist direction. So actually it is hard to avoid the panpsychist spread in anything short of something pretty drastically dualist, i.e. something that links mind uniquely to something far more restricted than matter (or electricity, or cellular structure, or functionality). It is not so much that materialism (and like doctrines) are too materialistic; it is more that they are too mentalistic—for they find mind spread far and wide and in the most unlikely of places. Materialism makes the whole physical world mental.
It is a good question how widely the net of panpsychism should be cast. People often say that atoms are to be construed as having mental properties (or “proto-mental” properties blah-blah-blah), as if this demonstrated the boldness of the doctrine. But that can hardly be the logical end of the line. What about electrons and protons? What about quarks and strings? Does panpsychism apply to points in an electromagnetic field? What about points in empty space? What about the laws of nature—are they also partly mental? And what about time—do instants have a mental dimension too? Mental events and processes occur in time, so is their temporal nature a result of the mental aspect of time itself? Or is it just plain old non-mental time transposed to the mind? But then won’t it be left unexplained how psychological time can exist? The logic of panpsychism is extremely far-reaching, making everything in the world a repository of the mental. Do numbers have a mental nature too? Are geometrical shapes mentally endowed? In any case, depending on how far we push panpsychism, materialism will require us to accept some version of it. Just by identifying pain with C-fiber firing we could end up claiming that space and time are bubbling with mentality! For C-fibers are just matter in one configuration, and it’s the matter that counts not its configuration (how could that—a matter of mere geometry—be what pain consists in?). If mind is associated essentially with this kind of matter, the kind in the brain, then it must be associated with all matter, on pain of denying the uniformity of nature (as well as invoking an ad hoc stipulation). Thus materialism turns out to presuppose panpsychism precisely because it seeks the basis of mind in matter. Being located in the brain does not alter the intrinsic nature of matter, so materialism is committed to the idea that matter as such is the basis of mind—and matter is everywhere. Only an arbitrary stipulation can prevent mind from cropping up wherever matter does. Fine, if you are OK with panpsychism, but not otherwise.
Note too that the same slide occurs on a less macro scale once we remember that not all of the brain is associated with mentality. Only some neural clusters are correlated with mental states, not all, yet they all share the same basic morphology and physiology. So it can’t be physical cell-type that makes the difference. The natural response is to declare that all the neurons in the brain are at some level endowed with mental properties, or else our materialism will be unacceptably arbitrary—what we could call pan-neural-psychism. But then the question will be why stop there—why not include heart and kidney cells? We have discovered that all the cells of the body have mental properties, given that we know that some of them do. The point is that it is impossible to stop the spread of the mind once we accept a materialist view of the mind as we locally conceive it. If C-fibers suffice for pain, or necessarily have pain as an aspect, then why don’t other fibers, whether in the brain or outside it? And why does it have to be fibers and not some other physical feature? To repeat, there is nothing special about the matter of the brain, even (especially) according to the materialist, so we can’t avoid inferring that mind must be present wherever there is matter. Universal mentalism follows from local materialism (not deductively, of course, but as a matter of overall theory). That is surprising perhaps, but not necessarily disastrous. From the point of view of the panpsychist, it turns out that grounds for believing materialism are grounds for believing panpsychism: if materialism is true, then panpsychism has to be true too, on pain of an arbitrary stipulation.
 See The Second Brain, by Michael Gershon (1998).
 I discuss such a view in “Can we solve the Mind-Body Problem?” (1989).
 It is generally accepted that it is not the color or location or size of C-fibers that matters to their being pain, so why should their shape make all the difference? It is the matter itself that is supposed to constitute the pain—but then why not pan-painism? What’s so special about neurons? They are just particularly stringy biological tissue, which itself is made of non-biological components.
 If the mental is the physical, then the physical is the mental, by the symmetry of identity. That is, if mental states are identical to certain physical states, then those states are identical to mental states, and hence the physical states necessarily imply the mental states (C-fibers are pain in every possible world). The point then is that there is nothing special about those physical states, so that panpsychism is the only reasonable position. They are not states with a special magical glow.