Excerpt From Chapter 1 of

The Manifest

By Mark Johnston
Princeton University

 

Physicalism

The robust independence of objects is respected by the second alternative to Projectivism, namely Materialism or Physicalism, the specific form of Materialism which treats the ontology of physics as exhausting the elements of being. The Physicalist is rightly impressed by the great explanatory achievements of physics, and taking it to be the most basic of the natural sciences he supposes that everything that goes on in nature has a physical description in terms which it can be located in the network of causes and effects. He then points out that if any particular has a genuine causal role in nature then physics will explicate that causal role in its own terms and describe how the particular has to be in order for it to have the role in question. Hence we get to describe Eddington's "second" table by giving a physicist's description of how the more familiar first table has to be in order to have the causal role it does. Now in one small step we move from physics to Physicalism: we say that therefore the familiar table is identical with Eddington's second table. Nonetheless the small step is a leap, since it certainly doesn't follow from the fact that the physicist has a description of the table adequate for the prediction of all the causal transactions the table could be involved in, that the whole nature of the table is exhausted by that description. At this point, the characteristic Physicalist move is to appeal to Occam's razor. Those who resist Physicalism are accused of multiplying entities beyond necessity as if the only alternative to identifying Eddington's two tables was to allow that there are in fact two tables. This not only misses an option, viz. that what Eddington calls his second table is really a Physicalist's account of the ultimate matter making up the familiar table, whereas the familiar table is this matter formed in a certain way; but also, as we shall soon see the very failure to distinguish the matter and the form of the table leaves the Physicalist without a plausible way to avoid multiplying tables indefinitely.

Collateral with this objection (to be developed in detail below) is the observation that few if any of the manifest qualities of the table seem equivalent to the quantitative properties which figure in the physicist's description of the table. In response to this, Physicalists try to divide and conquer. They say that some manifest qualities are none other than the physical quantities incompletely or misleadingly conceived, while others are indeed projected features of our experience and are therefore to be identified with quantitative properties of brain processes. Our question will of course be how the physicist's quantitative description of a brain process offers the materials to reduce apparent qualities of the manifest when his description of material objects does not. If cherry red fails to be identified with any quantitative property of objects is there a better hope that its spectral counterpart, the alleged mental quale cherry red*, can be identified with a quantitative property of a brain process?

A similar problem arises if we treat all such talk of mental qualia as a misleading way of talking about the content of experience. In the now preferred idiom of "mental content" the question becomes: if the mental content that this surface is cherry red is always false of the world as described by physics, how, if that world is the world, do we ever get to entertain such false contents? This is the issue which we will trace down in Chapter X, to the discredit of those Physicalists who hope to succeed by treating experience as the entertaining of representational content.

Again, these are technical issues which although crucial to the evaluation of Physicalism can obscure the central consideration. Physicalism cannot make room for the manifest because it cannot provide a physical reduction for manifestation, i.e. the continuous appearing or presenting to subjects of real features of other things and other people.

Although the appearing of an object to a subject requires a causal connection between subject and object, it is not to be identified with a causal connection. To leave it as a slogan, later to be filled out by an argument: when things are present to us they are "closer" than any mere cause could be.


A Fantastic Interlude: How Could Manifestation Just Be A Causal Process?

This, and not some backhanded defense of Mentalism against Materialism (old foes who now cooperate in a cartel in which each lives off the implausibility of the other so as to suppress competitors) is the real issue raised by Arnold Zuboff's telling variant of Ned Block's well-known "Nation of China" case.

Zuboff's thought experiment begins as follows. Consider the brain, the so- called "seat of consciousness" (even though consciousness is not the sort of thing which could sit or stand or even be as definitely located as a brain is.) If manifestation is to be a causal process then a crucial part of that causal process will have to involve he brain. For our purposes we can think of the brain as an organ packed with two kinds of cells. There's a large amount of sheer support material called glial cells, and these glial cells hold billions and billions, maybe in the typical brain about ten or eleven billion transducers called "neurons." The patterns of firing and inhibition of the neurons seem the most likely physical determinant of consciousness. There are of course very interesting and hard questions of brain chemistry which concern how the general chemical condition of the brain influences the secretion of neurotransmitters and allows transmissions across the synaptic gaps to create this or that pattern of firing and inhibition. Physically, at one useful level of description, all that's going on in a functioning brain relevant to the consciousness of the person whose brain is in question is the transmission of electrical impulses from neuron to neuron across certain gaps. At this level the neurons appear to be transducers operating according to input/output functions which are perhaps modifiable by the some of the inputs themselves.

Zuboff now imagines the invention of a new technology. We learn how to make extremely small radio transmitters and radio receivers. So small that it's now possible to transplant micro-transmitters and micro-receivers on each side of the synapses, and so replace the transmission of electrical impulses across the synapses by the leaking of neurotransmitters by sheer radio transmission.

The next step involves an engaging flight of fancy. The new technology allows us to take a person, say you, and isolate one of his functioning neurons. During an outpatient brain surgery, we remove a neuron of yours, but we keep it functionally connected to the rest of your brain and central nervous system by transplanting micro- transmitters and micro-receivers into that neuron and any and all neurons that were communicating with the neuron we take out. Because this radio transmission is quite a bit faster than the leaking of electrochemicals across the synapses, we can have your neuron still part of your functioning brain, even though it's kept alive in a little petri dish, at quite a distance from your person. (If that is the right way to put it.)

I'm slightly woozy already, so before we go any further lets step back and examine what we have done. We have unpacked a small part of your brain. We take out one neuron; with our new technology we keep it electrically connected with the rest of your brain and central nervous system; and we can do all this without interfering with your mental life. We've just expanded your brain in space a little. You're still conscious. Things are still manifest to you. The fact that the underlying physical process has changed somewhat doesn't seem relevant because we've preserved the functioning of the brain and central nervous system at the very level which seems relevant for the determination of consciousness.

Now the flight of fancy enters the stratosphere. We note that we can do this neuron by neuron, and so in the third step, we can expand your brain. After all, the fact that your brain is so densely packed isn't crucial to its being the organ that subserves your mental life. We can slightly expand your brain by taking out the neurons one by one in a very laborious and time-consuming process and so arrive at a situation in which we preserve a normal functional pattern of neural interaction. Even though your neurons are now no longer packed together tightly in side your skull but are separated out in, say, ten or eleven billion petri dishes, all communicating via these very small radio transmitters and receivers, there need be no interruption to your mental life. After all, all we've done is to take one process of transmission of neural signaling by way of the leaking of neurotransmitters and replace it via the slightly faster process of radio transmission. As a result, we separate out your neurons into the various petri dishes which keep alive and functioning the neural cells, communicating all the while in a functionally normal pattern. Perhaps, (if you like to enter wholeheartedly into the spirit of this) there are master receivers in your still embodied outermost sensory and motor neurons which allow you to wander around as if you had a brain in your head. Still your neurons are in fact spread out through, say, the Gibson Desert (which makes the Sahara look like a sandbox). That is where your "seat of consciousness" now happens to be.

Now for the imaginative equivalent of deep space. Looking at one of these petri dishes and the innocent little neuron sitting inside it, an obvious thought comes to us. What is this particular dish doing? Well, it's receiving signals. Then, according to a signaling function which has to do with the structure of the neural cell in question, but may be modified by some of the signals it actually receives, it passes on another set of signals. Think of the signaling function as a set of conditionals of the form: if such and such signals are received within a particular period of time and so and so signals are not received within that period then signal thus and so unless...in which case.... It occurs to us that the neuron in the petri dish represents only one physical way of carrying out the precise signaling function in question.

We could replace that neuron in that petri dish by a person who just receives and sends radio signals according to the very same signaling function.1 There is no physical reason why this should disrupt your mental life, things would be still appearing to you, you would still be conscious.

In for a penny, in for a pound. We next do the same for each of your neurons in the petri dishes. In place of your scattered brain, spread out over the whole of the Gibson Desert, we end up with ten or eleven billion people communicating with one another by way of radio transmitters and receivers. The pattern of signaling might be exactly that found in your brain the last time you enjoyed a good bacon sandwich. But are you now having the experience of enjoying a good bacon sandwich? Or any experience at all? Are you still hovering there over above those ten or eleven billion subjects of experience carrying out their frenetic signaling?

In such a bizarre case it would be unpersuasive to base anything on an intuition either way. This standard use of such cases to vindicate Dualism or the crucial importance of a biological realization like the brain (John Searle) or whatever by an "intuition" in a bizarre case thus represents a flawed philosophical methodology. There is however another use of this case, one which does not depend upon endorsing the intuition that you are still around alongside the frenetic signalers. We can instead derive something interesting from the certain claim that either you are still around or you are not.

That is to say that the point we are aiming for emerges on either way of taking the case. Suppose, as many do when confronted with this case, that you are no longer in the picture. What then was the crucial crossover point or sequence of steps in the process which led to the frenetic signalers from your enjoying experience of the world thanks to your brain functioning in its familiar location? How can the dense packing of one's neurons be crucial to the subserving of mental life? How can neural signaling by the leaking of chemicals rather than radio waves be crucial to the subserving of mental life? How can the actual physical realizer of a neuron's signaling role be crucial to the subserving of mental life? We do not have any way of making intelligible to ourselves how any of this is crucial. Nor does this seem to be merely a matter of ignorance of the fine details of neurophysiology. Specify those details however you like and we can run through a version of the same thought experiment. That is to say that our best physical description of the functioning of the brain does not make intelligible how that functioning subserves the presence to a subject of other things and other people.

Suppose alternatively that you are still in the picture, somehow consciously aware of your body's surroundings thanks to the frenetic signaling which has now taken over from your brain functioning. I think that it will be readily granted that if this is so it is none the less not intelligible how it is so. It is not intelligible how that complex, interactive, physical process of eleven billion people communicating with each other by way of radio transmitters and receivers could constitute the basis for a further subject of experience. What is also uncontroversial is that we arrived at that situation by a series of steps which neither individually or taken together do we understand to be the crucial move from something which was intelligibly the basis of mental life, to something which wasn't intelligibly the basis of mental life. For the steps just involve slightly varying the physical process in ways that seemed irrelevant to a physical process intelligibly being the basis for mental life.

Our thought experiment was wild, but not sterile. For it appears to show that either way our best physical description of the functioning of the brain does not make it intelligible how anything could appear to us. Nor does this seem to be an accidental limitation due to our presently incomplete understanding of neurophysiology.
This is a severe blow to the philosophical ambitions of Physicalism.
So far from providing a reductive account of the manifest, it cannot make intelligible how anything is manifest.

Let me reiterate that unlike many who employ such thought experiments, I do not take our fantasy to in any way raise the stocks of Mentalism or Dualism. As far as I can see, it is of no help at all in explaining how the manifest can be manifest to follow Sir John Eccles and add some mental stuff or mental causes to one's causal explanatory picture of the brain or the frenetic signalers. It simply creates the nearly intractable problem of meshing the extra mental causes with the apparently complete inventory of physical causes and effects.

So far as adding a soul goes, this would at least restore (though not reductively explain) the manifest, but only because to have a soul is inter alia to have the capacity to sense and to feel, i.e., to have other things, other people and their significance manifest to one. It is of course entirely unclear what special role mind stuff could have in grounding those capacities and hence in having a soul. Why can't a living human body be a good enough ground for a soul? Why can't the operation of one's visual system ground the making manifest to one of colors, shapes and other qualities in one's environment? The trick is not to require a physical explanation of how it could be so. But to abandon that requirement is to cease to be a Physicalist.

 

McGinn and The "Mystery of Consciousness"

Colin McGinn disrespects that last inference. He argues that one can cease to require a reductive physical explanation of how it could be so without ceasing to be a Physicalist. For McGinn thinks that as a species we are genetically disabled from formulating the right physical explanation of how the firings of neurons in the visual system or the operations of frenetic signalers could make manifest qualities appear to a subject. For McGinn our inability to find the right physical explanation is an ineradicable intellectual blind spot. Only an absurd overconfidence in human intellectual capacities would licence an inference from the fact that we have no idea where to look for a physical explanation of how things can be manifest to the claim that there is no physical explanation. Surely that is a perfectly decent caveat.

McGinn insists on more. He is prepared to venture the hypothesis that we will never know where to look. This is not brute pessimism on his part. He has a diagnosis of the general kind of explanation we are good at deploying. And he rightly observes that
this sort of explanation gets nowhere in the case at hand. In admitting that McGinn has gone further than many Physicalists.

Here is a diagnosis in the style of McGinn of why we are flummoxed when pressed for a physical explanation of how frenetic signaling or neuron firing could result in anything being manifest to a subject. (This is not the case McGinn focuses upon, but his account is meant to perfectly general.) First, according to McGinn we are adept at explanations which take what he calls the CALM form.


Our puzzlement over any way of taking Zuboff's case strongly suggests that no CALM theory connects a manifestation to a subject of a thing and its qualities with any efficient causal process, be that process neural or otherwise. So far, I think McGinn would agree.

However one thing that McGinn does not emphasize should be kept in focus. Physicalism is a strategy in philosophical ontology which aims to reproduce the CALM structure. The elements of being are the basic physical items, the modes of combination which generate from the elements the compounds which exhaust reality are the connections which physics recognizes. Indeed, the Physicalist's deployment of this or that refinement of the idea of supervenience no difference without an underlying physical difference -- is further evidence of reliance on the CALM structure. Supervenience was first introduced to me by David Lewis who used the example of cartoon faces drawn on graph paper. If the cells on the graph paper are small enough then facts about how cells are or are not filled in determine or fix the facts concerning whether a face is smiling, frowning or whatever. This fixing of the features of the large space by the features of the smaller spaces is a paradigm of the CALM structure. The supervenience here is plausibly taken to be an a priori matter, simply due to geometrical aggregation.

For another example, consider John Locke's account of the macroscopic properties of material objects. Locke works with three ideas already present in Galileo. First, material objects are made up of "insensible parts," very small invisible bits. Secondly, properties like shape, size, weight, motion or rest are for Locke part of the very notion of a material object --"inseparable from the idea of body" -- and so these properties are had by the insensible parts which make objects up. Third we can immediately see that when we combine things with these properties, the resultant combination always has a shape, size, weight and motion which is a direct function of the shape, size, weight and motion of its parts. Here is the CALM structure supposedly connecting an atomistic account of matter with material objects understood as bearers of primary qualities.

Whatever the success of the CALM structure in bridging any explanatory gap between the micro-physical and the macro-physical, nothing comparable is in the offing in the case of the physical and consciousness. Despite the plausibility of supervenience, very roughly, that every difference requires a physical difference, no detailed CALM structure makes intelligible just how physical processes could subserve mental processes such as the manifestation or presence of objects to subjects.

Nonetheless, McGinn insists on Naturalism or Anti-Dualism, surely the correct impulse. McGinn's philosophical despair amounts to his conviction that we cannot make intelligible to ourselves how Naturalism could be true here. Hence the so-called "mystery of consciousness".

The despair is a distraction, at least in the present context. If we are convinced of Naturalism and we recognize that Physicalism is wedded to the CALM structure then our reactions to any way of taking Zuboff's case shows that there must be room for a Naturalism which is not Physicalism. Hence the interest of Aristotelian Hylomorphism, which I take to involve an explanatory analogy that leaches away the puzzle of how a mental process could be subserved by a physical process. A form of that puzzle is, as we shall see, already present in the case of manifest material objects and the matter that makes them up. Locke succeeded only in making intelligible how the properties of the matter of material objects could be fixed by the properties of sub-parts of that matter. After all, it is a little noted consequence of Locke's account that no shape of a material object is named or described in ordinary language. The shapes of macroscopic aggregates of matter are too small scale to be seen and too complex and idiosyncratic to be described. So if the shapes of material objects are in fact seen by us, and I suppose they are, then the CALM structure is already wanting in the case of material objects. It does not encompass their manifest shape. Manifest shape supervenes on small scale physical shape. But the CALM structure associated with simple geometrical aggregation does not in fact bridge the gap. Here as elsewhere we have the fixing of the manifest features by the distribution of quantities through space-time, but no a priori derivation of the sort typical of the CALM structure. (See Chapter ..)



1. The person, as others have noted, would have to be very fast. But I am told that the video game maker Sega employs just such people to test their new games. What they are made of I do not know.