I am writing this as an expansion of my initial three-part series on natural theology. I said at the beginning of that series that there were a number of important arguments for theism which I would not be covering. Among these was the argument from consciousness, which asserts that the consciousness of ourselves and the other sentient animals provides grounds for believing in God. Here’s why I didn’t discuss it, even though I think the argument is very powerful. For there to be a special argument from consciousness, we must refute physicalism, which I understand here to be the view that we and our conscious states are, at the fundamental level, purely physical.  However, while I think there are good arguments against physicalism, at the time I wrote the earlier posts, I was not sure how to distill these arguments into something relatively brief and accessible. Well, I still don’t know how to make them brief; my discussion here will in fact be incredibly long. It will probably also be less accessible than the original series. But I hope it will be accessible enough.
This series will consist of seven posts. In this one, I will lay out some important concepts. In the second, third, and fourth posts, I will present a number of arguments which favor dualism over physicalism, where dualism is the view that the mental and the physical are equally fundamental, with neither being reducible to the other or to some third thing.  The second post will focus on defending property dualism, while the third and fourth posts will focus on defending substance dualism (both terms are defined below). In the fifth and sixth posts, I will discuss some arguments against dualism and explain why I don’t find them convincing. I will close with a final post defending the argument for theism for which the earlier posts laid the groundwork.
I mentioned in an earlier post that, when I was younger, science seemed like a threat to theism, insofar as it seemed like it might render God an “unnecessary hypothesis.” If the natural world could be explained on its own terms, you could still posit a creator, but why bother? I hope my earlier posts gave a sense of why I no longer feel that way. But I bring it up because I also used to feel the same way about dualism. I was (and am) aware of the fact that neuroscience has revealed more and more of the sophisticated correlations between our brain states and our mental states. There is every reason to think that it will continue doing so, and if it is not ultimately able to discover all of them, that seems likely to be because of limitations in ourselves or in our technology, not because the relevant correlations don’t exist. In light of this, while one of course could continue to believe that consciousness was something over and above the physical, didn’t our neuroscientific knowledge render this gratuitous? I now think I was just confused. The best arguments for dualism do not rely on the claim that neuroscientists will encounter some unexpected roadblock in the course of discovering psychophysical correlations; they rather claim that our increase in neuroscientific knowledge, interesting as it is, does little to explain why these correlations should obtain at all, or have the form that they do.
Or, anyway, so I shall argue. (Don’t worry, I will come back to the science stuff later in the series.) Before beginning, I will issue a caveat. I said at the beginning of my original posts that I could only hope to scratch the surface of the philosophical case for theism. The same is true of the arguments for dualism: I cannot discuss them all, and the arguments I do discuss are necessarily simplified. (I have tried to resist the urge to include every little distinction which is relevant to the following arguments, and to follow up on every little technical detail. I feel this urge because I want any of my philosophical colleagues who read these posts to know that I am aware of these things. But including them would have made the posts unreadable.) Further, there are a number of prominent arguments against physicalism which I will not cover, such as those involving intentionality (the “aboutness” of our thoughts), the “unity of consciousness,” or our ability to reason.  Interested readers can follow up by reading some of the more extensive scholarly treatments of dualism.
I’ll begin by clarifying some terms. The first is consciousness, which can mean all kinds of different things. Here, I will primarily mean what philosophers call phenomenal or qualitative consciousness. Phenomenally conscious states involve subjective experience. In the famous words of Thomas Nagel, there is “something it is like” to be in a phenomenally conscious state–to see a patch of red in one’s visual field, for instance. Philosophers often use the term qualia to refer to these subjective experiences. As Jaegwon Kim notes, the capacity for phenomenal consciousness is of the utmost importance. It is central to the value possessed by ourselves and the other sentient animals, and the nature of our phenomenally conscious experiences is central to the value our lives have for us. Kim writes:
When philosophers discuss the nature of the intrinsic good, or what is worthy of our desire and volition for its own sake, the most prominently mentioned candidates are things like pleasure, absence of pain, enjoyment, and happiness—states that are either states of conscious experience or states that presuppose a capacity for conscious experience. Our attitude toward sentient creatures, with a capacity for pain and pleasure, is crucially different in moral terms from our attitude toward insentient objects. To most of us, a fulfilling life, a life worth living, is one that is rich and full in qualitative consciousness. We would regard a life as impoverished and not fully satisfying if it never included experiences of things like the smell of the sea in a cool morning breeze, the lambent play of sunlight on brilliant autumn foliage, the fragrance of a field of lavender in bloom, and the vibrant, layered soundscape projected by a string quartet. Conversely, a life filled with intense chronic pains, paralyzing fears and anxieties, an unremitting sense of despair and hopelessness, or a constant monotone depression would strike us as terrible and intolerable, and perhaps not even worth living.
Not only are we intimately aware of our phenomenal consciousness, we are intimately aware of its immense significance. This significance will become important later, of course, since it helps explain why God might have an interest in creating conscious beings like us. For his part, Kim focuses on the value of phenomenal states themselves–the value of the sea’s smell, or the disvalue of chronic pain. And this value is great. But these states, in their value, also provide value to other features of our lives. For instance, our ability to affect the phenomenal states of other people and animals–to bring or prevent joy or pain to them–is a major factor in the valuable responsibility which we bear for one another. And our decisions about whether to sacrifice our pleasure, or undergo pain, for the sake of others provides a valuable way of developing and exercising virtue.
A second concept I will employ is that of a self, or, more precisely, a subject of experience. As is implicit in the above remarks, subjective experiences are necessarily experienced by an experiencer. (Or anyway, even if it is possible to have an experience without an experiencer, that isn’t how it is with us. Our experiences are had by experiencers–ourselves.) I will call an individual who has experiences (naturally enough) a subject of experience. You and I and my cats are, among other things, subjects of experience. A, the pain that I had five years ago, may be qualitatively more like B, the pain you had five years ago, than it is like C, the pleasant experience I am currently having. Yet A and C have at least one thing in common with each other and not with B: A and C were my experiences, whereas B was yours. If I unjustly inflict suffering on you, the reason I wrong you, rather than, say, Derek Parfit, is that the pain is yours, not his. If I repay a debt of gratitude to you by making it possible for you to have some exciting experience, the reason I repay my debt to you, and not to Derek Parfit, is that I made it possible for you to have the experience. And so on.
It may help here to consider the famous “floating man” thought experiment provided by Avicenna, widely regarded as the greatest Muslim philosopher of all time. (Among other things, he is responsible for inventing the argument from contingency for theism.) Avicenna asks each of us to:
…suppose that he was just created at a stroke, fully developed and perfectly formed but with his vision shrouded from perceiving all external objects – created floating in the air or in the space, not buffeted by any perceptible current of the air that supports him, his limbs separated and kept out of contact with one another, so that they do not feel each other. Then let the subject consider whether he would affirm the existence of his self. There is no doubt that he would affirm his own existence, although not affirming the reality of any of his limbs or inner organs, his bowels, or heart or brain or any external thing. Indeed he would affirm the existence of this self of his while not affirming that it had any length, breadth or depth. And if it were possible for him in such a state to imagine a hand or any other organ, he would not imagine it to be a part of himself or a condition of his existence.
In other words, we are to imagine a situation in which are not having, and have never had, any bodily sensations whatsoever. (Though Avicenna doesn’t say this, the floating man will presumably also need to lack any kind of propioception.) Avicenna suggests that, while in such a situation we would not realize we were embodied, we would nonetheless be aware of our own existence as beings with a point of view, with a mental life and a subjective perspective. What we would be aware of here is more or less what I am calling the self. In saying this, I am not presupposing that the self exists independently of the body or the brain. Perhaps I could be aware of my self qua self, and not aware of my body qua body, even though they are the same thing–just as I might, in some sense, be aware that Clark Kent is in the room, while not being aware that Superman is in the room, even though they are the same person. My point, for now, is just to explain what I mean in talking about the self, whatever its metaphysical nature.
Forms of Physicalism
Even trying to explain all this may make it seem more complicated than it really is. That we exist and have subjective experiences seems to go without saying. Accordingly, you may be surprised to learn that some philosophers reject the existence of qualia, and of ourselves conceived of as persisting subjects of experience. As Kim notes, “consciousness-bashing still goes on in some quarters, with some reputable philosophers arguing that phenomenal consciousness, or ‘qualia,’ is a fiction of bad philosophy… It is an ironic fact that the felt qualities of conscious experience, perhaps the only things that ultimately matter to us, are often… jettisoned outright as artifacts of confused minds.” Such denial often comes from physicalists who are worried–rightly, in my view–about the ability of physicalism to accommodate qualia and the self. People who reject some or all of our “folk” beliefs about our mental lives in the name of physicalism are known as eliminative materialists. (Many eliminativists also reject the existence of beliefs, which leads to funny questions about how to even state the view.) The arch-naturalist Alexander Rosenberg provides a particularly frank statement of this physicalist motivation for eliminativism, arguing that we need to reject the existence of a self since such a thing could only be an immaterial soul:
…if the mind is the brain (and scientism can’t allow that it is anything else)… we have to stop taking our selves seriously… We have to realize that there is no self, soul or enduring agent, no subject of the first-person pronoun, tracking its interior life while it also tracks much of what is going on around us. This self cannot be the whole body, or its brain, and there is no part of either that qualifies for being the self by way of numerical-identity over time. There seems to be only one way we make sense of the person whose identity endures over time and over bodily change. This way is by positing a concrete but non-spatial entity with a point of view somewhere behind the eyes and between the ears in the middle of our heads. Since physics has excluded the existence of anything concrete but nonspatial, and since physics fixes all the facts, we have to give up this last illusion consciousness foists on us.
(Reading the linked article will reveal that, in the name of naturalism, Rosenberg also rejects a number of other things which he argues cannot be reconciled with it, including the existence of right and wrong, “beliefs and wants, thoughts and hopes, fears and expectations,” purposive action, linguistic meaning–including, yes, the meaning of the sentences in the article–and “everything else we care about.”)
I don’t find this move convincing. I am being asked to give up on what could not possibly be more clear–that I exist as a subject experiencing qualia–in the name of a commitment to physicalism, which is certainly much less clear. Robert Adams, in his “Flavors, Colors, and God,” compares denying the existence of qualia as a way of avoiding problems for one’s naturalism to denying the existence of evil as a way of avoiding problems for theism, and says that “Eliminative optimism and eliminative materialism seem about equally implausible to me.” I actually think the latter edges out the former with regard to implausibility. But I nonetheless point out the existence of the eliminative materialist view partly to note that it isn’t only dualists who see a tension between qualia or the self, on the one hand, and physicalism, on the other. Many physicalists see the tension, too. Some, like Rosenberg, even agree that the tension is irresolvable, and that we must choose between consciousness and physicalism–though of course I think they make the wrong choice.
Most physicalists, however, attempt to reconcile these aspects of our mental lives with physicalism, rather than denying their existence. Some people used to think that life could not be reduced to the purely physical, that a mysterious élan vital was needed to explain some of the abilities of biological organisms. We now know this isn’t true. The biologists who showed that life could be accounted for in physical terms were not trying to prove that life didn’t exist, only that nothing over and above the physical was involved in it. They reduced life, rather than eliminating it.  Most physicalists want to do the same thing with consciousness. They suggest that my self is really just a physical object, such as my body or my brain. And they suggest that conscious states are ultimately just physical states of some sort. Perhaps, say, being in pain just is being in a certain kind of neurological or functional  state: there is nothing more to pain than just being in that neurological or functional state. (Make sure at some point to read the footnote attached to the word “functional” in that sentence. Functionalism will become important at a particular point near the end of the next post.)
Eliminative materialism, as I have indicated, does not seem to me to be worth worrying much about. So from here on out, my target will be the kind of physicalism that grants the existence of consciousness and the conscious subject.
In contrast to physicalism, we can distinguish between two different forms of dualism, property dualism and substance dualism. One is about consciousness and one is about the self. Property dualists claim (something like) that at least some of our mental states are not reducible to physical states. (It’s called “property” dualism because it claims that conscious beings instantiate two radically different kinds of properties, mental and physical ones, neither of which is reducible to the other or to something else.) I will treat it primarily as a thesis about phenomenal consciousness, so that the claim is that qualia are something over and above physical phenomena. The physicalist must deny this. They must say either that qualia do not exist, or else that they are somehow nothing over and above the physical.
Property dualism does not commit us to any particular view about the self: it does not commit us to saying that these irreducible conscious states are the states of an immaterial soul. Perhaps I, the subject of my experiences, am a brain or a body, but brains or bodies have more to them than we realized: in addition to their ordinary physical properties, they also (sometimes) have radically different, irreducibly mental properties. We can refer to a view like this–which grants that consciousness is an irreducible phenomenon, but denies the existence of an immaterial substance–as mere property dualism. The arguments I present in the next post are arguments for property dualism, but do not distinguish between mere property dualism and substance dualism (though some philosophers have argued that mere property dualism is an unstable position, so that these arguments should lead one to substance dualism after all). It is important to note that, for purposes of the argument for theism which I will present, mere property dualism is enough. However, in the third and fourth posts, I present arguments for substance dualism as well as for property dualism. The more the merrier.
Substance dualism, meanwhile, is the claim that conscious beings involve two different kinds of substances, both physical matter and an immaterial soul. When we are speaking strictly, we might say either that I am a composite of both a body and a soul, with my soul being the essential and ultimately more important part, or else just (the view I prefer) that I am a soul which bears a certain kind of special causal relationship to my body. As I will understand it, substance dualism identifies the subject of experience with the soul; the soul is what experiences qualia. It is therefore does commit us to a view about the self, namely that it is an immaterial substance. I will present several arguments specifically for substance dualism.
Substance dualism of the sort I will defend is sometimes called “Cartesian dualism,” after its most famous proponent, René Descartes–the father of modern philosophy, and a character who will reappear in some later posts. I accept the “Cartesian” label on the condition that, of course, it doesn’t entail my agreeing with all the details of how Descartes fleshed out his view. For some details, this goes without saying: nobody nowadays think the pineal gland plays the special role Descartes gave it. But as someone who works professionally on the ethical treatment of animals, I will single out one particular detail. Probably Descartes’ most sinister and ridiculous view was that non-human animals lack souls, and therefore lack the ability to feel pain, and are therefore fair targets for vivisection and other forms of abuse. Perhaps the most generous thing that can be said on Descartes’ behalf was that support for vivisection was the norm among “men of science” of that era, who generally dismissed opposition to it as allowing mere sentiment to get in the way of the pursuit of knowledge. (Apparently this attitude persisted for some centuries, judging from C.S. Lewis’ essay “Vivisection,” reprinted here.) What really seems to have driven the vivisection was not, as some claim, a superstitious commitment to dualism, but rather a commitment to pursuing science over the objections of those with moral qualms.
Anyway, Descartes’ rejection of animal consciousness is not essential to the view. (Indeed, his reasons for rejecting it are at best reasons for thinking animals lack the capacity for reasoning or abstract thought, not that they lack the capacity for conscious experience.) I take it as beyond dispute that animals have conscious experiences. The arguments I provide, if successful, will entail that any subject of experience is a soul. Since they entail this, and since I claimed that all experiences must have subjects, my arguments entail that any conscious being possesses an immaterial soul, and therefore (since many non-humans are conscious) that many non-humans possess one as well. If dualism has sometimes been used to justify a kind of chauvinism in favor of humans, mine should not be: if anything, it should lead us to a renewed appreciation of our fellow spiritual creatures. (And of course, the same will apply if conscious artificial intelligence is ever developed, which as far as I know is possible in principle.)
Anyway, enough setup. In the next post, I start arguing for dualism.