Memory and Knowledge

What is the connection between memory and knowledge? To judge from the standard literature, very little—in a typical treatise on knowledge memory is hardly mentioned. I wish to urge a strong connection: all knowledge is memory knowledge. Memory enters into every instance of knowledge; all knowledge presupposes memory knowledge. That is, all present-tense knowledge depends upon knowledge derived from the past. I don’t just mean that inferential knowledge derives from premises stored in memory—though that is true enough—I mean that even the premises rest upon antecedently possessed knowledge. If I now judge that there is a cup on my desk, this piece of present-tense knowledge requires that I possess knowledge acquired in the past. The reason for this is that in order so to judge I must already know what a cup is: I must have that knowledge stored in my memory. I must have the concept of a cup (as well as the concept of a desk and myself), and having a concept is an epistemic state. My memory interacts with my current experience to deliver the knowledge that there is a cup on my desk. If my memory were blank in this respect, I would not be able to make such a judgment. This is a point about human knowledge not about all logically possible types of knowledge: it is conceivable that a being should acquire knowledge of the same proposition at the same time as acquiring the concept of a cup. But as things are with humans that is not the case: we first have the concept and then use it to formulate the knowledge in question. According to traditional empiricism, the concept derives from perception of cups in the past, traces of which are stored in memory—a concept is an abstraction from perceived objects retained in the mind over time. According to nativism, a concept is an innate item of knowledge that persists in the mind over time. Strictly speaking, it is not stored in memory but in something analogous to memory: an informational storehouse of some sort. At any rate, it exists in the mind as a result of past events—it functions like a memory proper. It exists in the mind unconsciously and occasionally reaches conscious awareness in the form of explicit knowledge. Thus for both theories present knowledge depends upon past knowledge, because it depends on the prior existence of suitable concepts. You can’t know something now unless you already knew something earlier. Knowledge is a cross-temporal phenomenon.

            This makes knowledge different from experience. You can have an experience now without having had any prior experience: I can see a cup now without having seen one before, or seen anything before. Present experience doesn’t depend upon past experience. It is like bodily sensation: having a pain now doesn’t depend on having had pains in the past, or having had any sensations. Pain is an at-a-time phenomenon. Accordingly, it is perfectly possible to have an experience of a cup and yet fail to recognize the presented object as a cup. You could lose your memory of what a cup is and still see one. Similarly, you could forget who John is and yet still see him: you no longer know the identity of the presented person yet he can still come within your field of vision. But you can’t know that John is in front of you without knowing who John is—that is, having the individual concept John. Knowledge is made of concepts, and concepts are remnants of the past (whether stored in individual memory or “species memory”). Present knowledge always depends on past knowledge. Note that this is not regressive: the past knowledge is not knowledge-that but knowledge-what. To know that there is a cup on the desk you have to know what a cup is, but this latter knowledge is not a type of knowledge-that. If it were, knowledge would be impossible: for then the knowledge would depend on an antecedent piece of propositional knowledge, which would require another piece of propositional knowledge, and so on ad infinitum. But conceptual knowledge is not propositional knowledge, so there is no regress. The thesis being defended might more cautiously be stated as follows: all propositional knowledge presupposes non-propositional knowledge (which takes the form of memory). First we have conceptual knowledge (knowing-what), and then we have propositional knowledge (knowing-that). We never have a piece of propositional knowledge that is independent of our past epistemic state (this applies equally to self-knowledge). We never know anything about the present that derives wholly from the present.

            This position stands opposed to acquaintance models of knowledge—theories that regard knowledge as simply a type of perception. But we can never know a proposition simply by being acquainted with its subject matter at a given time, as if this knowledge were splendidly cut off from the past. Seeing is not the same as knowing. For knowledge requires classification—bringing something under a concept—and concepts pre-date their exercise in acts of propositional knowledge. I can’t even know that I am in pain by pure acquaintance, since I need to apply the concept pain, and that concept stems from my epistemic storehouse. I must already know what pain is in order to judge and know that I am currently in pain. I can feel pain without any antecedent preparation, but I can’t know that I am in pain without already knowing something about pain. Such knowledge is a coordination of past and present not merely a momentary act of acquaintance. That idea is a myth—an empiricist myth—born of modeling knowledge too closely on perceptual experience. There is a deep distinction between knowledge and experience; the former is never a special case of the latter.

            How does this conception of knowledge fit the case of the a priori? The answer is: not smoothly, but this shows something important about a priori knowledge. Suppose I judge that the number 3 is prime: to do this I need to know what a prime number is and what the number 3 is. Does my knowledge result from applying this prior knowledge to my current experience of 3? It does not: I don’t have any such experience. I am not presented with the number 3 and then dredge up my concept of that number, along with the concept of a prime. There is no analogue of perceptual experience to combine with antecedently possessed concepts. If I didn’t have the concept three, I couldn’t be confronted with the number 3. Numbers can only come before the mind as so conceptualized. There is no perception of numbers that leaves it open whether the object in question is a number, or the number it is. There is no pre-conceptual apprehension of numbers.^[1] Still, in order to make the judgment that 3 is prime I need to bring to bear my prior knowledge of numbers, i.e. my mathematical concepts. So the basic thesis applies to the case of a priori knowledge: propositional a priori knowledge depends on non-propositional conceptual knowledge. Knowing-that depends on knowing-what. It is just that we don’t have the combination of experience and cognition that we have in the empirical case. This is one way that the a priori differs from the a posteriori: such knowledge is not “by experience”, i.e. it requires no triggering perceptual input. Putting the point in terms of memory, propositional mathematical knowledge requires memory knowledge concerning what the objects of interest are—numbers, sets, geometrical forms. Thus mathematical knowledge involves a type of remembering, as empirical knowledge does: both are excavations of the cognitive past. The faculty of memory is being exercised as knowledge is acquired; and this is a deep-seated fact about human knowledge (if not all logically possible knowledge). Knowledge is not separable from memory. As memory takes us back to the past, so knowledge takes us back to the past—it is backwards looking. Remove someone’s memory and you remove his knowledge. New knowledge is inseparable from old knowledge. This is obvious for inductive knowledge, since we need to remember past observations, but it is also true for non-inductive empirical knowledge and for a priori knowledge. In acquiring any item of knowledge the past is always operative in the present. When knowledge is defined as true justified belief (or some such), not only is the justification typically derived from past observation; the very possibility of forming the belief in question derives from a prior epistemic state. Recollection is always in the picture. Both empiricism and nativism tacitly recognize this necessary involvement with the past: empiricism by holding that all knowledge depends on past experience in the form of stored perceptual encounters; nativism by locating the basis of knowledge in what is cognitively present at birth. Knowledge always has a history—in the individual and in the species. Only a kind of misplaced epistemic atomism could suppose otherwise—the idea of knowledge as an isolated quality of a time-slice. Perhaps experience can be conceived that way, but not knowledge. Realistically, knowledge always builds on the past, cumulatively and derivatively; it never descends from the sky and installs itself in the mind ab initio. Memory is what makes knowledge possible.^[2]

Colin McGinn                  

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^[1] The same can be said of other entities of which we have no experience: concepts themselves, platonic forms (the Good), and the self. In these cases we have no pre-conceptual experience of the entity in question, so that there is no presentation of these entities to the mind that leaves open what they are. We are never in doubt about what is before our mind. For example, we can never misidentify the Good as something else—an elephant or the Bad, say. 

^[2] As a corollary, skepticism about memory always dogs human knowledge: if our memories are radically in error, our knowledge is doomed. Memory is fallible, so knowledge based on it is always subject to doubt. 

Phenomenological Behaviorism

Could it be that there is an element of truth in behaviorism? Behaviorism is usually presented as a third-person view of the human mind—what we know of the mind by external observation. It often goes with a materialist metaphysics. It therefore naturally incurs the charge of ignoring the first-person perspective—of overlooking the mind’s phenomenology. But can’t we also motivate it by taking an inward view—by considering what the mind is like from the inside? Thus consider pain: isn’t the experience of pain essentially bound up with avoidance behavior? When you feel pain you instinctively avoid the painful stimulus—you withdraw from it, are averse to it, avoid it at all costs. You don’t feel pain and find yourself attracted to the painful stimulus, or indifferent to it—you want to get away from it, so that it stops hurting you. You behave in a certain way as a result of the pain, and this behavior is written into the experience: pain is inherently that which initiates avoidance behavior. Even if you can’t actually behave this way, you are strongly inclined to—you desire to, urgently. Pain is not behaviorally neutral; and this is a matter of its phenomenology, not just something tacked on. The same can be said of pleasure, only now the behavior is attraction not repulsion, approach not avoidance. Desire is much the same: you want to do what will satisfy your desire—you want to behave in a certain way, e.g. eat. These mental states are partly behavioral: not wholly, because there is also a subjective aspect, but partially. The state is a kind of hybrid of the phenomenal and the behavioral, to put it crudely. Behaviorism might thus be said to be partly true: behavior (or dispositions to it) is certainly not the whole of the mind, but it is at least a part of it—necessary if not sufficient. And this is a phenomenological fact not the result of a methodological stipulation: the mind feels behavioral–from the inside, from the first-person point of view. Just remember your last serious pain and how intensely your body wanted to escape the painful stimulus. The pain is subjectively behavioral—its subjective mode is AVOID.

            This is not to say that actual behavior is necessary to the existence of mind: paralysis is possible with full mental preservation. It is to say that behavioral inclinations, desires, plans, tendencies and urges are part of the experience of pain. Let me put it this way: the body image is integral to sensation—if not the physical body itself. We mentally represent our own body—proprioception being the main vehicle of bodily representation—and this representation is built into our sensations. Sensations are intertwined with the body image, including its dynamic aspects. This is equally true of perceptual sensations: visual experience is intertwined with awareness of the eyes as they point and move; tactile experience with the whole touchable and mobile body; auditory experience with the ears; smell with the nose; taste with the mouth. All of this is behavioral, because the sense organs move and orient themselves: they are behaving organs. The same is not true of the brain: we have no brain image that accompanies our every mental episode—as we have no liver image or kidney image. The muscles and the mind, however, are deeply interconnected—those makers of movement, large and small. Emotions too have their behavioral expression: flight, fight, laughter, and copulation. They are not indeed exhausted by their behavioral manifestations, but the behavior is part of their phenomenological character—as real as any other part. We are accustomed to recognizing that mental states have intentionality—they are about things—but we must also recognize that they have a kind of secondary intentionality in relation to the body: they represent the body in its active mode. Time is also part of their phenomenology, in addition to the objects they are about; and the body is yet another dimension of phenomenology. A visual experience, say, is made of the following components: an intentional object, an experienced time, a subjective mode, and an ocular organ.^[1] It is not some sort of primitive atom of subjectivity, as in the mosaic model of consciousness, but a tightly structured other-referring entity—and the body’s (apparent) behavior is part of this complexity. The movement of the eyes, much studied by psychologists, is built into the phenomenology of vision: I experience the visual object as seen by my mobile eyes, detected and scanned by those nimble bodily organs. Visual experience is behaviorally imbued. Thus behaviorism is a phenomenological fact—subjective first-person behaviorism. Mentalistic behaviorism not materialistic behaviorism: behavior as initiated and apprehended from within, part of the body image. Consciousness itself is behaviorally inflected. Phenomenology is always bodily phenomenology—partly at any rate.

            Consider those tireless winging bats again (our philosophical helpmates): when they use their sense of echolocation they simultaneously and inextricably mentally represent their own flying bodies, particularly ears and mouths (where the echoing shrieks originate). That is the behavioral phenomenology of bat echolocation. This is something we can in principle grasp—for we know what it’s like to be aware of our ears and mouths. We may not grasp the subjective modality of the bat’s experience entirely, but we do grasp an aspect of it—the behavior-directed aspect. We know what it’s like to be a sense-organ aware creature. We grasp the nature of the bat’s body, so we grasp the behavioral aspect of bat experience (they are mammals after all). There is, we might say, an objective aspect to the bat’s subjective experience—the aspect corresponding to the bat’s behavioral phenomenology. Just so, the blind man can grasp the objective aspect of visual experience, i.e. the part that involves ocular awareness (he is aware of his eyes by proprioception). So sensory experience is partly objective, because partly behavioral, though not wholly so. Partial behaviorism affords partial objectivity, i.e. general availability. The mistake of old-time behaviorists was to push the element of truth in behaviorism too far: first, by exaggerating its reach; and second, by adopting a third-person perspective. But there is room for a type of phenomenological behaviorism that acknowledges the first-person perspective; indeed, such a behaviorism seems unavoidable, given the embodied nature of the mind. The mind is phenomenologically in the body, directing it, responding to it: it is part of what the mind is constantly aware of. We (and other animals) are phenomenological activists, steeped in awareness of our own behavior.

            But here is the puzzle, the enigma: how does a mental state combine its behavioral dimension with its subjective (“qualitative”) dimension? It is not as if pain consists of an ordered pair of a quale and a behavioral disposition: the two do not just sit side by side without meshing together. On the contrary, the avoidance aspect is integral to the felt aspect: pain could not be anything other than an avoidance-inducing sensation. There could not be a being that experienced pain and yet felt no avoidance with respect to it (contrary to what is sometimes said about masochists): the sensation of pain is essentially an aversive phenomenon. This is, in the jargon, an a priorinecessity.  Moreover, the subjective and behavioral are internally connected not merely externally conjoined. We have a two-factor theory in which the factors are inseparable from each other. The sensation breaks down into two elements, but the elements are not really separable: we have a conceptual distinction without an ontological distinction. This is puzzling (more so than two-factor theories of propositional content)—the objectively behavioral seems to have taken up residence in the most subjective aspects of the mind. The eyes are a part of seeing! So let us accept that the truth of partial behaviorism leads to a deep puzzle, which may help to explain why it has not occupied a place in thinking about the mind. Total behaviorism at least avoids the problem of the subjective-behavioral nexus—as total subjectivism also does. The hybrid conception courts the problem without solving it. Not that this counts against the theory for a resigned mysterian—indeed, mystery is par for the course. The truth is often mysterious. Still, we should acknowledge that partial phenomenological behaviorism does give rise to a difficult problem (analogous to the general mind-body problem): the problem of integrating the behavioral with the subjective—or seeing the subjective as imbued with the behavioral. The behavioral follows from the subjective, rather than being opposed to it—and that is a puzzling fact. What is it like to be a bat? Look at the bat’s body and imagine its internal mental representation of its own body: that is part of what it’s like for the bat—along with the more elusive matter of its specific subjective experience. And that latter thing embeds the former thing inextricably.

            Nor are the puzzles quite over yet. What about thought, particularly abstract thought—does it have a behavioral aspect? That is not so obvious: does introspection reveal a phenomenological aspect relating thoughts to a bodily organ or part? Are there specific things that thought inclines us to do (like desire, pain, emotion, etc.)? Doesn’t it seem pretty damned disembodied? Maybe thought is an exception to partial phenomenological behaviorism—it has zero behavioral phenomenology. Maybe it belongs to the immortal incorporeal soul, as some have regarded Reason. One possibility is that it is connected to language and thence to speech: vocal behavior is its behavioral accompaniment (or sign language). It is just that its behavioral aspect is more remote than normal, but still essential. Or is the head somehow involved—clutching it, cradling it (as in Rodin’s Thinker)? It does seem right to distinguish degrees of behavioral involvement: some mental states have a larger behavioral component than others—pain a lot, perception rather less, belief even less. Maybe thought is just at the far extreme of behavioral disengagement—only tinged with the behavioral not flooded with it. It may not be purely subjective (removed from everything behavioral in its essential character) but has its finger lightly on the behavioral pulse. On the other hand, if it were resolutely non-behavioral that would be an interesting result, meriting the headline, “Thought Not Behaviorally Contaminated According to Scientists”. I won’t attempt to resolve the issue here, having merely noted it. The important point is that for many types of mental state a (partial) behavioral phenomenology is strongly indicated. The doctrine of behaviorism, which held sway for quite some time, is not completely without merit of motivation—though, ironically, its main rationale stems from introspection. The introspectionist psychologists should have been behaviorists! For we necessarily appear to ourselves introspectively to be behaving beings. Our consciousness is (partly) a behavioral consciousness. This is just to say that the body exists on the horizon of the mind.^[2]

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^[1] More controversially, we could add the self to this list: an experience presents an object to a subject in such a way that the subject is part of the phenomenology too. There is a reference to the self in every mental act. An experience is thus a phenomenological quintuple consisting of a subject, an object, a subjective mode, a time, and a behaving body. This is a far cry from the simple “idea” or “impression” of traditional philosophy of mind—the analogue of an elementary atom of matter. I would call it a multi-aspect theory of mental phenomenology. The mental points in several directions simultaneously. 

^[2] This is to be distinguished from the idea that the mind is as a matter of objective fact essentially embodied; it is rather the thesis that the mind is experienced as embodied (and no doubt is). The mind is embodied as a matter of its phenomenology, even when its intentional object is not the body itself. The behaviorism is virtual rather than real (though no doubt it is also real).

Epiphenomenal Facts

Epiphenomenalism is the doctrine that mental facts (properties, events, states) are causally idle. When it seems as if mental facts are causing behavior it is really correlated neural facts that are doing the causing—electrical signals sent from the brain down the efferent nerves and into the muscles. This is taken to be a singular fact about the mental: it is uniquely lacking in causal powers. Even in the case of a steam engine emitting waste steam—the standard analogy for epiphenomenalism—the steam can cause something, possibly burns in someone too close to it. The mental is thought exceptionally idle, and this is taken by many to be an objection to epiphenomenalism—too much of an anomaly. But is that true—are there no other epiphenomenal facts in the world? In fact, they seem quite plentiful upon closer examination. Obvious examples would be mathematical and ethical facts: they don’t cause anything either, but they are real. Nor is this merely contingent: it is intrinsic to such facts that causality be foreign to them. The same is true of such properties as identity, existence, necessity, and set membership—none of these feature in causal explanations or confer causal powers. Ditto for logical properties such as entailment and validity: these have no causal consequences either. Does the property of being a cause itself have causal consequences? Nope. These may be thought rather abstract properties, unlike mental properties, but we can easily find more concrete properties that likewise fail of causal potential. Colors are an obvious example: colors don’t cause anything either—only their underlying physical correlates do. If colors are projected onto the world, it is predictable that they make no difference to the causal powers of the objects onto which they are projected—subtract them and the object remains causally indistinguishabe. This is why mechanics makes no mention of colors in its theories of motion (red balls move the same way as blue balls). Acceleration and mass affect the causal powers of bodies, but not color (or taste etc.). Epiphenomenalism is all around us.

            And it doesn’t end there. Do space and time have causal powers? Not inherently—not independently of material objects (even in Einstein’s General Relativity). Does infinity have causal powers? Does the infinite divisibility of space and time show up in the causal powers of things? Would it make any difference to the causal workings of the world if they were finite? It is not clear that it would. Is it even clear that geometrical forms have causal powers? Does it really make a difference to how objects behave whether they instantiate perfect circles? Causality is not fine-grained enough to care whether objects are platonically perfect. Causal powers in the physical world stem from four underlying forces: gravity, electromagnetic force, the strong force, and the weak force. But these operate independently of the geometrical and chromatic properties of objects: being a perfect circle (or an imperfect one), or being a whiter shade of pale, are not their concern. Mass matters, for sure, but not platonic forms or visual appearances. Of course, it matters whether an object is circular or rectangular in the vernacular sense, but not its fine-grained geometry. This is too abstract and ideal to be of concern to the rough and tumble of causality. In fact, objects don’t instantiate perfect platonic forms, though they do approximate to them, but it wouldn’t make any causal difference if they did.^[1]

            This is all before we get to such peculiar properties as being thought of by Bertrand Russell one Saturday afternoon. Whether an object has this property makes no difference to its causal potential. Nor does the property of being round and such that 1 +1 = 2. Nor does the property of having a counterpart in another possible world. These are all far too extrinsic to count as causal powers. But mental properties are not extrinsic, so shouldn’t they have causal powers? Let’s consider functional properties, e.g. having the function of pumping the blood. The heart has this property: is it causal? It is not: the heart doesn’t pump blood in virtue of having the function of doing so. It pumps blood in virtue of its elastic and propulsive properties—the properties that enable it to discharge the function it has. The heart could have that function and not have the power to pump blood (it’s a defective heart). No more does a lawn mower cut grass in virtue of having the function of mowing lawns—for that it needs sharp blades and forward momentum. Having a certain function is not part of the causal powers of an object; having the properties that carry out that function is. So we could say that functional properties are epiphenomenal: they are facts but not causal facts. Just so, an organism has many functional properties that are causally idle, corresponding to its various organs. The color of blood is epiphenomenal, but so is its function per se. Functions are not causes. Teleology is not causality. Nor is species membership a cause: being of a certain species is not something that makes a causal difference, not in itself. True, members of a species have the power to interbreed, but not in virtue of species membership—for that they need a certain kind of physiology. Properties that sit idly by are certainly correlated with hardworking causal properties—and this may mislead us into thinking that they are less than completely indolent—but closer inspection reveals that they are not as such causally active. The pattern is that epiphenomenal properties sit atop causal properties—as functional properties are embodied in causal properties without being identical to them. 

            This is the picture the epiphenomenalist envisages for the mental and the cerebral. Mental facts are strictly speaking epiphenomenal facts, but they are tightly correlated with causal machinery in the brain. Is this a plausible view of mental facts? In the case of factive mental states like knowledge it certainly seems true: whether a belief counts as a case of knowledge is irrelevant to its power to affect behavior—being true is not a causally relevant property (the same for whether a perceptual experience is veridical). Intuitively, factives are too extrinsic to function causally. But much the same holds for propositional content generally: even a bit of externalism will have the result that content is epiphenomenal.^[2] And how could an abstract proposition contribute to the causal powers of a belief? The causal powers of beliefs evidently derive from underlying brain states, possibly of a syntactic nature (this is a familiar story). Beliefs as such don’t cause behavior, but only the correlates of belief; or if you like, beliefs have a causal aspect but they are not causal through and through. Thus intentionality generates epiphenomenal facts, which is not very surprising—being about something is not the kind of property that can get muscles to contract. More interesting is the property of subjectivity: is what it’s like subjectively epiphenomenal? To be a subjective state is to be such that the nature of the state can only be grasped from a single point of view, i.e. by a being that shares the state in question. Only perceivers of red can grasp what it’s like to see red. This is an epistemic property of a mental state: it can only be known in a certain way. But how could that property contribute to the causal powers of the state? How could the state cause behavior in virtue of being knowable only in a certain way? Maybe material objects can only be known about in a certain way, i.e. by perception, but that has no bearing on their causal operations—physics doesn’t care about such epistemic questions. So the subjectivity of mental states isn’t part of their causal profile—which means that what an experience is like for its possessor isn’t part of its causal profile. The fact that we can’t know what it’s like to be a bat doesn’t affect the causal powers of bat experience—it carries on causing bat behavior irrespective of what we can know. Presumably bat experiences cause bat behavior in virtue of various objective facts about the bat’s brain—electrochemical activity, as we now believe.^[3] In one clear sense, then, consciousness is epiphenomenal—it doesn’t cause behavior in virtue of there being something it is like. Of course, we can truly say of a conscious experience that it caused an episode of behavior, because it has a cerebral aspect or correlate; but we can’t infer from this that its conscious aspect is itselfa causal power. That is, given that a conscious property is not identical to a brain property, it does not have causal powers. We can loosely report that an experience of red caused someone to move in a certain way, but we can’t mean that the subjective nature of the experience acted causally—only that an underlying physical correlate did. Logically, the case is like saying that the color red caused someone to see red: it is not the color as such that does the causing but only its physical correlate in the object. Colors themselves are epiphenomenal, but that doesn’t preclude the existence of a correlated causal sequence leading from object to experience. Similarly, conscious states are epiphenomenal, but that doesn’t preclude the existence of a correlated causal sequence leading from brain to behavior. After all, epiphenomenal facts are common in nature, as we noted, and consciousness simply follows suit. It is not anomalous in this respect but typical.

            This solves a difficult problem. If conscious states had intrinsic causal efficacy, then we would have causal over-determination, since brain states also cause behavior. Each would be sufficient to cause the behavior in question, which means the other cause is not necessary. It may appear that the only way out is to identify the conscious state and the brain state, thus committing ourselves to reductive materialism. But a viable epiphenomenalism allows us to avoid this result while not accepting causal over-determination: it is the brain state alone that is doing the causing—the conscious state sits idly by, serenely epiphenomenal. The conscious state is numerically distinct from the brain state and the brain state is the sole cause of the behavior—because the conscious state has no causal role to play in producing the behavior (not intrinsically and as such). Thus epiphenomenalism allows us to escape a difficult problem without succumbing to reductionism. Nor is this merely ad hoc since epiphenomenal facts are quite common in nature—the norm, we might say. The metaphysical picture is that nature has two layers: an underlying layer of causal machinery, which is quite restricted, and an overlying layer of epiphenomenal properties that coast on the first layer. A perfectly reasonable hypothesis is that the causal layer consists of nothing beyond the four fundamental forces identified by physics; the rest of nature is not in the causal line of business (save derivatively). It is thus quite wrong to think of nature as exclusively composed of causal facts. The four basic forces do all the causal work while the rest of nature stands by without lifting a finger.^[4]

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^[1] Causation is all about the induction of motion, but pure geometry lies beyond this. Which geometry holds of nature need not impinge on the causal machinery of nature.

^[2] Reference is causally irrelevant, notoriously. Where is the energy emitted by the reference relation? 

^[3] The brain itself has various epiphenomenal properties over and above its conscious properties, so not everything about it is causally implicated in behavior—for example, its color, its taste, its precise furrowing, and its spatial location. If the brain qua brain has epiphenomenal properties with respect to the causation of behavior, then surely the mind can. Among the epiphenomenal properties of the brain are its mental properties.

^[4] This means that if you were to remove the four forces from nature leaving everything else intact all causation would be expunged. This seems like a plausible result—even the basic atomic entities are nothing causally without their accompanying forces. They are certainly not epiphenomenal.

Dualism Naturalized

Traditional dualism is characterized by two theses: (a) the mind is a separate substance (object, entity) from the brain, and (b) the mind is immaterial. These are logically independent; in particular, (a) does not entail (b). The mind could be a separate physical substance from the brain, existing alongside it. Or neither could be physical, since the concept of the “physical” is irredeemably ill defined, ever since mechanism was abandoned in the wake of Newton’s introduction of action-at-a-distance. Descartes believed both (a) and (b), holding that matter is defined by extension and mind by thought (which is not extended). But if we give up on that way of defining the difference between mind and body, we can assert that the mind is not identical with the brain (or body generally) and yet is not immaterial. Neither is the brain “physical” in any useful sense, since it harbors powers and forces not recognized by traditional materialist science (electromagnetism, notably).^[1] According to modern physics, the brain consists of fields and quantum states not hard little lumps of impenetrable matter. In any case, we are under no logical obligation to describe the brain as physical and the mind as non-physical, as if this reported anything of serious significance. The brain is a biological organ, to be sure, but so is the mind—whether identical to the brain or not. So it is logically open to us to maintain that the brain and the mind are separate things—separate biological organs—without getting caught up in the matter of immateriality. The important question is not whether one is “material” and the other “immaterial” but whether they are the same or not. That is the question of dualism (versus monism) not the question of whether the world contains any immaterial substances as well as material ones. This latter question we can happily discard as antiquated, while the former question can legitimately command our attention. If the mind is indeed a separate substance from the brain, it is available as the subject of psychological predications; it is not the brain that is the bearer of mental states but the mind. Or the self, if we prefer to speak that way: the self is the thing that thinks and feels, senses and acts. According to dualism, the self exists as a separate entity from the brain, i.e. the two are not numerically identical (this is compatible with certain kinds of dependence). We can say this without buying into some supposed dichotomy of the material and the immaterial: we can be dualists without being immaterialists. We just decline to talk in that style or, if we are wedded to it, we describe the mind as another sort of physical thing—rather as earlier physicists agreed to describe electromagnetism as physical even though it was of a different nature from what had hitherto been rated “physical”. The better question is whether there are minds or selves distinct from bodies and brains: are we composed of two sorts of thing or one?

            And there are good reasons to return the answer two. For minds and selves are not individuated as bodies and brains are, as many thought experiments from the theory of personal identity show. Brains and minds have different identity conditions and don’t necessarily track each other over time or at a time: the brain can remain in existence while the mind perishes; a single mind can conceivably occupy different brains (by uploading or gradual replacement of parts); a person can survive the removal of half of his brain while brain itself is no longer fully intact; and so on. Brain and mind have different criteria of identity. The right thing to say here is that just as there are emergent properties so there are emergent objects: selves or minds are biologically emergent objects, stemming from brains no doubt, but not reducible to them. We need a robust ontology of such entities (get your quantifiers ready!) as well as the ontology of bodies and brains.^[2] If we ask what the nature of these extra entities is, we have a number of options: we can stick to appearances and declare their nature to be nothing other than what is supplied by our ordinary talk of the mental, or we can postulate a hidden nature the terms of which currently escape us. The latter alternative allows us to suppose that the second substance has a real essence (as Locke would say) that could in principle be discovered and investigated, analogous to the chemical structure of familiar substances. Maybe cognitive science is even now mapping this hidden terrain. In either case we need not be silent on the question of nature: the mind or self has a nature proper to it just as the brain and body do. It is just that these natures are different. Of course, there is interaction between the two, and a dependence of mind on brain, and an interlocking of function—but not numerical identity.^[3] The case is like the distinction between lungs and heart: not the same things but plenty of interplay.

            To what extent do these separate entities share attributes? Here is one notable overlap: both are temporal. Brain processes take place in time, and so do mental processes. Both things are temporally extended (unlike abstract entities such as numbers). Descartes never denied that, merely insisting that the mind is not spatiallyextended. This is actually quite a concession, because it locates both mind and body in the same world of changing perishable phenomena—in nature, in one sense of that pliable term. And then there is the possibility that the temporal must have a foot in the spatial, if time and space have any necessary connection. In any case, the mind shares with the brain the attribute of temporal existence. What about spatial extension itself? The question is not straightforward: admittedly, the mind does not belong to phenomenal space—we don’t see it as thus extended—but it might nevertheless belong to noumenal space, whose nature may be capacious enough to include it. Maybe the mind is extended in this possibly unimaginable space—it takes up some of it. Certainly it exists cheek by jowl with spatially extended matter, so one might suppose that it cannot be quite removed from space; conceivably the two join together in a type of space that defies our ordinary conceptions. So, pace Descartes, we might allow that thought has a spatial aspect, even though we have no perception or conception of it. Actually I think this idea has a good deal to be said for it, but I won’t go into that now; it is enough to remark that the two substances could resemble each other in point of space and time while still being genuinely distinct. This would be quite different from classic forms of metaphysical dualism.

            Surely this picture fits the case of animals better than the religiously tainted picture in which the immortality of the soul must be guaranteed. The mind of an octopus, say, which is remarkably rich, is not identical to its widely distributed brain, but it can hardly be deemed “immaterial” in the sense that it could exist without the octopus’s body and brain. Its mind is an adaptive organ, evolved from more primitive attributes, and not to be identified with its brain (ditto the octopus self)– yet the metaphysics of the immaterial substance hardly fits the case, or the immortality of the octopus soul (sadly). We can allow ourselves to speak of these things as distinct from the octopus’s body without incurring the charge of immaterialism. Dualism is alive and well but it is no longer in cahoots with immaterialism. There is nothing “unnatural” about accepting that the mind is an entity distinct from the brain—that is, a type of substance dualism. And there is nothing supernatural either—nothing evidencing divinity. Given that we already accept a dualism of properties, this is indeed the natural way to go: we need a suitable object to go with these properties, to be their proper subject. There was always something funny about ascribing mental properties to brains and their parts for fear of raising the specter of the immaterial soul.^[4]            

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^[1] I won’t go into the full rationale for saying this here; it has been well documented elsewhere (Chomsky et al). 

^[2] The metaphysical background to what I am saying here is supplied by all those puzzles of identity we are familiar with: the statue and the piece of bronze, organisms and the matter that composes them, objects and the property bundles that characterize them, etc. Leibniz’s law does the heavy lifting in distinguishing objects we might lazily have supposed identical.  

^[3] You might try to respond by conceding the non-identity of mind and brain but contend that the former is constituted by the latter, thus preserving the spirit of materialism. The case is like the relation between a statue and the lump of matter that composes it: not identity, since they have different persistence conditions, but constitution—there is nothing more to the statue than the stuff that composes it. But this analogy fails, because it is not that the mind simply has to assume a certain shape to be what is: the mind isn’t the brain in a certain geometrical form. If there is a constitution relation here, it is nothing like the familiar paradigms. Similarly, we can’t model the mind-brain relation on, say, the relation between water and its constituent molecules: the mind is not a collection of physical constituents, viz. neurons. So the dualism is far more pronounced than these alleged models would suggest, and hence identifying the mind with the brain is a far more problematic position. In fact, we really have no idea how to understand this relation; we only know that the mind is a thing distinct from the brain, in both the identity and constitution senses. But the general nature of the link between mind and brain appears sui generis.

^[4] There are those who proudly describe themselves as property dualists but wouldn’t be caught dead defending substance dualism. This paper is intended to allay their qualms by making some necessary distinctions. The main point is that mere ontological dualism has no immaterialist implications: all that follows is that the mind is not a congeries of neurons (with only the properties ascribed to neurons in current neuroscience).