There is a crucial difference between these two cases. All other integrations into a super-science, of sciences dealing with entities and properties apparently qualitatively very distinct, was achieved by saying that really some of the entities and properties were not as they appeared to be; by making a distinction between the underlying (not immediately observable) entities and properties and the phenomenal properties to which they give rise. Thermodynamics was conceived with the laws of temperature exchange; and temperature was supposed to be a property inherent in an object. The felt hotness of a hot body is indeed qualitatively distinct from particle velocities and collisions. The reduction was achieved by distinguishing between the underlying cause of the hotness (the motion of the molecules) and the sensations which the motion of molecules cause in observers. The former falls naturally within the scope of statistical mechanics — for molecules are particles; the entities and properties are not now of distinct kinds. But this reduction has been achieved at the price of separating off the phenomenal from its causes, and only explaining the latter.

Computers function as they do because they have been constructed by human beings endowed with rational insight. And the results of their computations are accepted because they are evaluated by rational human beings as conforming to rational norms. A computer, in other words, is merely an extension of the rationality of its designers and users, it is no more an independent source of rational insight than a television set is an independent source of news and entertainment.

So far no attempt at naturalizing content has produced an explanation (analysis, reduction) of intentional content that is even remotely plausible. A symptom that something is radically wrong with the project is that intentional notions are inherently normative. They set standards of truth, rationality, consistency, etc., and there is no way that these standards can be intrinsic to a system consisting entirely of brute, blind, nonintentional causal relations. There is no mean component to billiard ball causation. Darwinian biological attempts at naturalizing content try to avoid this problem by appealing to what they suppose is the inherently teleological, normative character of biological evolution. But this is a very deep mistake. There is nothing normative or teleological about Darwinian evolution. Indeed, Darwin's major contribution was precisely to remove purpose, and teleology from evolution, and substitute for it purely natural forms.

More to the point, brain processes, composed as they are of meaningless chemical components, seem as inherently devoid of intentionality as soundwaves or ink marks. Any intentionality they have would also have to be derived from something else. But if anything physical would be devoid of intrinsic intentionality, whatever does have intrinsic intentionality would thereby have to be non-physical. Since the mind is the source of the intentionality of physical entities like sentences and pictures, and doesn't get its intentionality from anything else (there's no one "using" our minds to convey meaning) it seems to follow that the mind has intrinsic intentionality, and thus is non-physical.

We are compelled to admit between the thoughts of a terrestrial astronomer and the behaviour of matter several light-years away that particular relation which we call truth. But this relation has no meaning at all if we try to make it exist between the matter of the star and the astronomer's brain, considered as a lump of matter. The brain may be in all sorts of relations to the star no doubt: it is in a spatial relation, and a time relation, and a quantitative relation. But to talk of one bit of matter as being true about another bit of matter seems to me to be nonsense.

Once, then, our thoughts were not rational. That is, all our thoughts once were, as many of our thoughts still are, merely subjective events, not apprehensions of objective truth. Those which had a cause external to ourselves at all were (like our pains) responses to stimuli. Now natural selection could operate only by eliminating responses that were biologically hurtful and multiplying those which tended to survival. But it is not conceivable that any improvement of responses could ever turn them into acts of insight, or even remotely tend to do so. The relation between response and stimulus is utterly different from that between knowledge and the truth known. Our physical vision is a far more useful response to light than that of the cruder organisms which have only a photo-sensitive spot. But neither this improvement nor any possible improvements we can suppose could bring it an inch nearer to being a knowledge of light. It is admittedly something without which we could not have had that knowledge. But the knowledge is achieved by experiments and inferences from them, not by refinement of the response. It is not men with specially good eyes who know about light, but men who have studied the relevant sciences. In the same way our psychological responses to our environment — our curiosities, aversions, delights, expectations — could be indefinitely improved (from the biological point of view) without becoming anything more than responses. Such perfection of the non-rational responses, far from amounting to their conversion into valid inferences, might be conceived as a different method of achieving survival — an alternative to reason. A conditioning which secured that we never felt delight except in the useful nor aversion save from the dangerous, and that the degrees of both were exquisitely proportional to the degree of real utility or danger in the object, might serve us as well as reason or in some circumstances better.

Each illusory self is a construct of the memetic world in which it successfully competes. Each selfplex gives rise to ordinary human consciousness based on the false idea that there is someone inside who is in charge. The ways we behave, the choices we make, and the things we say are all a result of this complex structure: a set of memeplexes (including the powerful selfplex) running on a biologically constructed system. The driving force behind everything that happens is replicator power. Genes fight it out to get into the next generation, and in the process biological design comes about. Memes fight it out to get passed on into another brain or book or object, and in the process cultural and mental design comes about. There is no need for any other source of design power. There is no need to call on the creative 'power of consciousness', for consciousness has no power. There is no need to invent the idea of free will. Free will, like the self who 'has' it, is an illusion. Terrifying as thought seems, I suggest it is true.

Defenders of materialism usually use three types of arguments to criticize the family of arguments I presented earlier. They use Error replies if they think the item that the antimaterialist is setting up for explanation can be denied. They use Reconciliation objections if they suppose that the item in question can be fitted within a materialist ontology. Moreover, they also use Inadequacy objection to argue that whatever difficulties there may be in explaining the matter in materialist terms, it does not get us any better if we accept some mentalistic worldview such as theism. We can see this typology at work in responses to the argument from objective moral values. Materialist critics of the moral argument can argue that there is really no objective morality, they can say objective morality is compatible with materialism, or they can use arguments such as the Euthyphro dilemma to argue that whatever we cannot explain about morality in materialist terms cannot better be explained by appealing to nonmaterial entities such as God.

The process whereby man has come to know the universe is from one point of view extremely complicated; from another it is alarmingly simple. We can observe a single one-way progression. At the outset, the universe appears packed with will, intelligence, life, and positive qualities; every tree is a nymph and every planet a god. Man himself is akin to the gods. The advance gradually empties this rich and genial universe, first of its gods, then of it colours, smells, sounds and tastes, finally of solidity itself as solidity was originally imagined. As these items are taken from the world, they are transferred to the subjective side of the account: classified as our sensations, thoughts, images or emotions. The Subject becomes gorged, inflated, at the expense of the Object. But the matter does not rest there. The same method which has emptied the world now proceeds to empty ourselves. The masters of the method soon announce that we were just mistaken (and mistaken in much the same way) when we attributed "souls" or "selves" or "minds" to human organisms, as when we attributed Dryads to the trees. Animism, apparently, begins at home. We, who have personified all other things, turn out to be ourselves mere personifications. Man is indeed akin to the gods, that is, he is no less phantasmal than they. Just as the Dryad is a "ghost," an abbreviated symbol for certain verifiable facts about his behaviour: a symbol mistaken for a thing. And just as we have been broken of our bad habit of personifying tees, so we must now be broken of our habit of personifying men; a reform already effected in the political field. There never was a Subjective account into which we could transfer the items which the Subject had lost. There is no "consciousness" to contain, as images or private experiences, all the lost gods, colours, and concepts. Consciousness is "not the sort of noun that can be used that way."

The idea that an ultimate source of being and becoming is to be found in the purely mental and non-physical is at odds with the conception of mind espoused by most contemporary philosophers. It is commonly held that mental states are to be characterized in terms of their causal role, but since such states are thought to be states of the brain, there is no lessening of a dependence on the physical. This is not a position I wish to invoke. It is doubtless true that we could not believe, desire, or intend without a brain, but any attempt to construe belief and the rest as states of that organ involves a serious mismatch between the psychological concepts and physical reality. Beliefs can be obsessive, unwavering, irrational, or unfounded, but nothing inside anyone's head answers to such descriptions.

If we are to attribute intelligence to any entity — limited or unlimited, cosmic or extra-cosmic — we have to take as our starting point our concept of intelligence as exhibited by human beings: we have no other concept of it. Human intelligence is displaced in the behavior of human bodies and in the thoughts of human minds. If we reflect on the active way in which we attribute mental predicates such as "know," "believe," "think," "design," "control" to human beings, we realize the immense difficulty there is [in] applying them to a putative being which is immaterial, ubiquitous and eternal. It is not just that we do not, and cannot, know what goes on in God's mind, it is that we cannot really ascribe a mind to God at all. The language that we use to describe the contents of human minds operates within a web of links with bodily behavior and social institutions. When we try to apply this language to an entity outside the natural world, whose scope of operation is the entire universe, this web comes to pieces, and we no longer know what we are saying.

Let me begin by nailing my colours to the mast. I count myself a materialist, in the sense that I take consciousness to be a species of brain activity. Having said that, however, it seems to me evident that no description of brain activity of the relevant kind, couched in the currently available languages of physics, physiology, or functional or computational roles, is remotely capable of capturing what is distinctive about consciousness. So glaring, indeed, are the shortcomings of all the reductive programmes currently on offer, that I cannot believe that anyone with a philosophical training, looking dispassionately at these programmes, would take any of them seriously for a moment, were it not for a deep-seated conviction that current physical science has essentially got reality taped, and accordingly, something along the lines of what the reductionists are offering must be correct. To that extent, the very existence of consciousness seems to me to be a standing demonstration of the explanatory limitations of contemporary physical science. On the assumption that some form of materialism is nevertheless true, we have only to introspect in order to recognize that our present understanding of matter is itself radically deficient. Consciousness remains for us, at the dawn of the twenty-first century, what it was for Newton at the dawn of the eighteenth century: an occult power that lies beyond the pool of illumination that physical theory casts on the world we inhabit.

I believe that the explanatory gap in its present form cannot be closed — that so long as we work with our present mental and physical concepts no transparently necessary connection will ever be revealed, between physically described brain processes and sensory experience, of the logical type familiar from the explanation of other natural processes by analysis into their physico-chemical constituents. We have good grounds for believing that the mental supervenes on the physical — i.e. that there is no mental difference without a physical difference. But pure, unexplained supervenience is not a solution but a sign that there is something fundamental we don't know. We cannot regard pure supervenience as the end of the story because that would require the physical to necessitate the mental without there being any answer to the question how it does so. But there must be a "how," and our task is to understand it. An obviously systematic connection that remains unintelligible to us calls out for a theory.

So, I would maintain that there are gaps and there are gaps. It is not just pointing to an unsolved engineering problem in nature. First of all, the categories of the mental and the physical are logically incompatible categories. You start attributing mental properties to physics and you might end up being told that you are no longer describing the physical at all. Purpose, normativity, intentionality, or aboutness, all these things are not supposed to be brought in to the physical descriptions of things, at least at the most basic level of analysis. ¶ Let us consider the gap between the propositional content of thought and the physical description of the brain. My claim is that no matter in how much detail you describe the physical state of the brain (and the environment), the propositional content of thought will invariably be undetermined. ... As I see it, it is not a matter of getting a physical description that will work. In my view, the logicoconceptual gap is always going to be there regardless of how extensively you describe the physical. As I said earlier, bridging the chasm is not going to simply be a matter of exploring the territory on one side of the chasm. ... [T]he "God of the gaps" or even a "soul of the gaps" response to the argument from reason does not work. I am not saying that we just cannot figure out right now why the mental states involved in rational inference are really physical, I am suggesting on principled grounds that a careful reflection on the nature of mind and matter will invariably reveal that there is a logical gap between them that in principle cannot be bridged without fudging categories.

Can we gain any deeper insight into what makes the problem of consciousness run against the grain of our thinking? Are our modes of theorizing about the world of the wrong shape to extend to the nature of the mind? I think we can discern a characteristic structure possessed by successful theories, a structure that is unsuitable for explaining consciousness. ... It there a "grammar" to science that fits the physical world but becomes shaky when applied to the mental world? ¶ Perhaps the most basic aspect of thought is the operation of combination. This is the way in which we think of complex entities as resulting from the arrangement of simpler parts. There are three aspects to this basic idea: the atoms we start with, the laws we use to combine them, and the resulting complexes ... I think it is clear that this mode of understanding is central to what we think of as scientific theory; our scientific faculty involves representing the world in this combinatorial style.

Physicalism] seem[s] to be in tune with the scientific materialism of the twentieth century because it [is] a harmonic of the general theme that all there is in the universe is matter and energy and motion and that humans are a product of the evolution of species just as much as buffaloes and beavers are. Evolution is a seamless garment with no holes wherein souls might be inserted from above.

Having convinced only a small fraction of Americans that chance and tautology — i.e. Darwinism — adequately explains life (despite a court-ordered monopoly on public education for the last half-century), materialists are moving on to your mind. Materialism posits that your mind is meat. No soul, no spirit, just chemicals, congealed by natural selection to dupe you into believing that you’re more than an evanescent meat-robot. It’s a hard sell, but that’s not to say that materialists haven’t tried. In the first half of the 20th century, behaviorists proposed that internal mental states were irrelevant or didn’t exist at all. All that mattered in the study of the mind was stimulus and response. Behaviorism turned out, unsurprisingly, to be a sterile avenue of research, as one might guess about a theory of the mind that denied or ignored mental states. As a theory of the mind, it is now largely regarded as insane, even by materialists. Behaviorism may be the only scientific theory to be finally extinguished by a joke: After a night of passion, one behaviorist rolls over in bed and says to the other: "that was good for you; how was it for me?"

It is possible that a materialistic explanation of consciousness might be found, but that does not make the claim that consciousness is non-physical an argument from ignorance... At any given time, scientists should infer the best current explanation of the available evidence, and right now, the best evidence from both neuroscience and rigorous philosophical analysis is that consciousness is not reducible to the physical. Churchland’s refusal to draw this inference is based not on evidence, but on what Karl Popper called "promissory materialism," a reliance on the mere speculative possibility of a materialistic explanation. Since this attitude can be maintained indefinitely, it means that even if a non-materialist account is correct (and supported by overwhelming evidence), that inconvenient truth can always be ignored. Surely the project of science should be one of following the evidence wherever it leads, not of protecting a preconceived materialist philosophy. Isn’t it that philosophy — the one that constantly changes its shape to avoid engagement with troublesome evidence, either ignoring the data or simply declaring it materialistic — that most resembles a virus?