Do We Perceive the Corporeal World?

Happily, however, it has come to pass that this claim has been formidably challenged by a neuroscientist named M. R. Bennett, in collaboration with an Oxford philosopher named P.M.S. Hacker, who give the following response:

This is at best misleading, since in perception the brain learns nothing—it is the person whose brain it is that perceives and learns something in perceiving. What we see does not appear to be located outside us. What we see is necessarily located outside our body… The neurons without which we would not see anything are located in our heads, but, of course, it is not those neurons that see or that “do” the seeing… There is no sense in which “the world” is in anyone’s head…²

These clear and eminently sensible observations will no doubt be welcomed by many as a breath of fresh air. Yet granting the validity of Bennett and Hacker’s realist stance, the question remains how the prodigy of perception is actually accomplished. It is of course to be understood that the neuronal structures in the visual cortex of the brain do have an essential role to play, as Bennett and Hacker presume; yet it is far from clear, at this point, what precisely that role might prove to be.

Crick himself almost admits as much when he tells us that “we can see how the brain takes the picture apart, but we do not yet see how it puts it together,”³  a statement based upon two assumptions, both of which prove to be false: for the first so-called “picture”—the one the brain is said to “take apart”—is in fact the so-called retinal image, which actually is not a “picture” at all, whereas the second—the one the brain is unable to produce—turns out to be the mountain or the tree we happen to be looking at.

But whereas Crick is evidently mistaken regarding what it is that we perceive, he is right in pointing out that the brain itself cannot get us there. What confronts us in this impasse, first of all, is the ontological difficulty of making one thing—be it a mere image or an external object—out of many: out of the on/off states, in this instance, of a myriad neurons in the visual cortex of the brain. This is the famous “binding problem” which has engaged top-level neuroscientists for decades, with no resolution yet in sight.

I would note, first of all, that based upon their realist view of visual perception, Bennett and Hacker appear to dismiss this pressing question as a pseudo-problem:

For the color, shape, location and movement of the blue delphiniums swaying in the breeze cannot be taken apart (there is no such thing as separating these attributes from the objects of which they are attributes), and the color, shape, location and movement of the delphiniums cannot be brought together in the brain, since these attributes are not to be found in the brain, either together or separately.⁴

Yet regardless of whether it makes sense to speak of “separating the color from delphiniums,” doubts arise when they maintain that “it is precisely this confusion [between the blue delphiniums swaying in the breeze and whatever may be found in the brain] that informs the neuroscientists’ characterization of the ‘binding problem’.” For whereas Bennett and Hacker are unquestionably right in pointing out that “this confusion” has profoundly affected the neuroscience community, it would be a serious mistake to dismiss the issue per se as a pseudo-problem. For even after the aforesaid misinterpretation has been diagnosed and corrected, the question remains how a neuronal mechanism can be associated with a unitary perception of the external world, inclusive of its motions and colors.

There is thus, most assuredly, an authentic “binding problem”; and though that problem may be at variance with the formulation generally imposed by neuroscientists, it proves to be no less profound and no less intractable under Cartesian auspices. Even from the perspective of Bennett and Hacker, moreover, there must, in the final count, be a unifying principle to “bind” the multitude of neurons—inclusive of their on/off positions—failing which the entire neuronal mechanism would evidently be irrelevant to visual perception. Or to put it another way: if indeed the brain acts as a computer—which hardly anyone doubts—there must be something or someone, in effect, to “read” that computer: to bring into unity what, on the level of the physical brain, is fragmented into a myriad of microscopic components. But that “principle” is something our scientists are de facto unable to conceive, for it happens to be the very conception excluded from our Weltanschauung by the Cartesian Ansatz itself. I wish, however, to point out that the restoration of that crucial component—its reintegration into our worldview—can in fact be effected with ease: one need actually look no further than the ontology of St. Thomas Aquinas, which refers to that element as a “substantial form.”

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This fact should come as no surprise. After all, the substantial form of an animate being is none other than what is traditionally termed a soul:⁵  and there was a time, not so very long ago, when every child knew that each of us has one. But getting back to the binding problem: it is evidently the soul that “binds” not only the neurons in the visual cortex, but every discernible component of the body into the unity of the living organism. Is it any wonder that—having jettisoned this crucial component—we should face a “binding problem”!

The question arises, of course, how the soul or substantial form itself can accomplish the seemingly miraculous feat of “uniting” an unspeakably vast multitude of entities—be they neurons, “atomic particles,” or what you will—into a single living organism; and let me emphasize that the formal re-introduction of substantial forms in itself hardly resolves the mystery. To grasp what actually stands at issue it is needful also, obviously, to have some insight into the nature and resultant powers of that soul. And to this end it behooves us to avail ourselves of what some have termed cosmologia perennis: the cosmological wisdom, that is, transmitted by the great sapiential traditions of mankind. What will concern us, in particular, is the tenet that the cosmos at large, no less than the human microcosm, proves to be ontologically tripartite: that like the latter, it is made up of three “levels” answering to the designations corpus, anima, and spiritus.⁶  What is it, then, that distinguishes these three ontological domains? It proves to be the bounds of space and time, I maintain: for whereas the corporeal domain is evidently subject to both space and time, the intermediary (sometimes termed the “astral” plane) is subject to time alone, while the spiritual is subject to neither. The essential point, now, regarding “souls” is that they pertain to the intermediary domain, which is to say that they are subject to time but not to space. And here at last we have the “missing” piece of the puzzle: for it is by virtue of being “supra-spatial,” precisely, that the soul has the capacity to “bind” into one substance, one living organism, a multitude of spatially separated components—billions of neurons, for instance, in the visual cortex of the brain. No wonder the neuroscientists are baffled; for it happens that the binding problem is in fact insoluble on the corporeal plane.

Getting back to Bennett and Hacker: we fully concur that perception does not take place on the level of neurons, and that “the brain does not ‘construct a perceived world’, but enables the animal to see a visible scene.” And we concur likewise when they go on to say:

Since seeing a tree is not seeing an internal picture of a tree, the brain does not have to construct any such picture. It merely has to be functioning normally so that we are able to see clearly and distinctly. It does not have to take a picture apart, since neither the visual scene nor the light array falling on the retinae are pictures. It does not have to put a picture back together again, since what it enables us to do is to see a tree (not a picture of a tree) in the garden (not in the brain).

It could hardly have been put more clearly! My point, however, is that these observations do nothing to resolve the binding problem, but rather bring to light its seeming insolubility insofar as they expose the ontological chasm that separates the firing of neurons from the seeing of a tree.

It is possible, of course, to ignore the problem: to simply let neurons be neurons and trees be trees. Yet the impasse remains, and the philosopher, more profoundly than the neuroscientist, will have failed in his mission unless he discovers the element or principle connecting the percipient to the object perceived. And that is—like it or not—where metaphysics enters irrevocably into the discourse. What is called for, as I have stated before, is the time-honored conception of the soul as the substantial form of the living organism, along with the realization that this soul (traditionally termed psyche or anima), unlike the components it binds, is not subject to the divisions of space. It is the resultant “transcendence of spatial separation” on the part of the living organism that resolves the binding problem.

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Having ascertained that we do actually perceive a tree in the garden as distinguished from a mere image of the tree, we arrive finally at the decisive question: how does neuronal activity enter into the process of visual perception? What role, precisely, do neurons play in that process: why, in fact, are they needed at all? Now, I know of only one cognitive psychologist who has successfully answered this question on empirical grounds—and oddly enough, Bennett and Hacker do not so much as mention his name. I am referring to James J. Gibson, who began his career at Cornell University in the early 1940’s on a government research grant, devising tests to ascertain whether a prospective pilot could effectively detect the aiming point of a complex motion, and discovered to his amazement that the physical data available in the so-called “retinal image” do not suffice to determine that point. Then and there he recognized what his colleagues have apparently failed to grasp to this day: namely, that this fact alone disproves the premise upon which the prevailing “image theory“ of visual perception is based. At one stroke Gibson realized that every domain of research pertaining to visual image psychology—for instance, the massive endeavor, resulting in hundreds of articles, purporting to explain how the so-called “third dimension” is supposedly constructed from retinal data—is doomed from the outset to fail.⁷  In a word, Gibson realized that the theory of visual perception stands in need—in desperate need—of a new paradigm.

And thus began a quest spanning decades of painstaking empirical inquiry, vigorously pursued by a hard-headed no-nonsense empiricist averse to scientistic fairy-tales. And in course of time a new paradigm did emerge from these labors, giving rise to a brand new theory: the “ecological theory of visual perception” Gibson calls it, to emphasize that what is normally perceived resides neither in the brain nor in the consciousness of the percipient, nor indeed in the world as conceived by the physicist, but in what Gibson terms the environment, which is thus reminiscent of what I term the corporeal world. What we perceive turns out, after all, to be a mountain that can be climbed or a tree in the garden, as humanity has in fact believed from time immemorial.

It would take us far beyond the scope of this article to present so much as a summary account of Gibson’s revolutionary theory of visual perception.⁸  I wish rather to reflect upon the astounding fact that this “ecological” theory has actually broken the Cartesian stranglehold and re-established realism—in fact what some might term “naive realism”—on rigorous empirical grounds. Gone is the twin fantasy of res cogitantes and res extensae! The redness of a rose, it turns out, is not after all what Galileo conceived to be a “secondary” quality, a mental apparition mistakenly projected upon a colorless external entity. Following four centuries of utter confusion, it turns out that roses are indeed red, and that the “simpletons” have proved to be wiser than the pundits of the Enlightenment, who to this day have failed to realize that they are living in a fantasy world—or, better said, would be if they actually believed what they affirm.

Suffice it to say that the crux of Gibson’s discovery resides in the recognition that visual perception is based, not on a so-called retinal image (which actually does not exist), but upon what he terms invariants to be found in the ambient optic array, which prove to be inherently what traditional philosophers refer to as forms. It proves to be these forms that provide access to the external world, to “the blue delphiniums swaying in the breeze.” For as Aristotle noted long ago, it happens that the very being of material entities consists, not of what is nowadays termed “matter,” but yes—of forms. It is only by way of forms, therefore, that the perception of an external object can actually take place. Bravo, James J. Gibson: you deserve ten Nobel Prizes at the very least!

The great question, now, is how that Gibsonian “pickup of invariants” is actually accomplished, and how, moreover, the complexities unearthed by contemporary neuroscience fit into the emerging picture. The first thing to be noted in that regard is that the “computer” paradigm is simply not up to the task: admittedly it may explain this or that secondary phenomenon, but when it comes to the central issue—how we perceive, not a mere image of whatever kind, but actual corporeal entities—on that score it gives us not so much as a clue. A neuronal computer, like any other, is after all equipped to handle what electrical engineers term Shannon information, and as such it does presumably have a role to play; yet by no stretch of the imagination can a computer of any kind—even one “made of meat”—pick up or transmit Gibsonian invariants: color for instance.

It turns out, moreover, that the pickup of invariants from the ambient optic array requires movement, demands in fact a search: and this alone disqualifies the erstwhile “camera” paradigm of visual perception. For whereas a camera can produce a succession of static images, that is not what we actually perceive. What we perceive is the result of a search which involves much more than the eye conceived as a camera. The requisite receptors must, for example, include the muscles responsible for those exceedingly rapid eye-movements known as “microsaccades,” which play a decisive role in that “pickup of invariants.” The actual “instrument of visual perception” comprises thus a substantial part of the human anatomy in addition to the eyes and visual cortex. It turns out, moreover, that this “instrument” cannot, strictly speaking, be conceived in mechanistic or Cartesian terms. Gibson himself does not perhaps bring this out as clearly as one might wish: he is after all an empiricist, not a metaphysician. Yet even so it emerges from his findings that the actual instrument of visual perception does not in fact reduce to “the sum of its parts,” which is to say that the Gibsonian pickup does not reduce to a mechanical process.⁹  Hard as it may be for the post-Enlightenment mind to conceive, we are dealing actually, not with a robot, but with a living organism! The perceptual system, so far from functioning as a mechanism, is in fact animated by the substantial form of the living organism: the very form traditionally termed a soul. Not only, thus, is that soul needed to “bind” the neurons in the visual cortex as noted before, but it is in fact required to “bind” the entire organism, and in so doing render it both living and sentient.

It needs hardly to be pointed out that Gibson’s theory of visual perception proves to be epochal in its significance and implications—which oddly enough appears to be the reason why only a comparative few have so much as heard his name: for one can see at a glance that the Gibsonian breakthrough suffices de jure to bring down our post-Enlightenment Weltanschauung in a single stroke. The fact is that in refuting the Cartesian epistemology, Gibson has disproved the fundamental premise upon which our supposedly “scientific” worldview rests to this day. We must not expect to see statues of him erected any time soon.

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Yes, we do perceive the “external” world, and we perceive it primarily with the sense of sight—which is after all why one speaks of a Weltanschauung, a “world-view.” One may take this a step further to say that, for us, the world is in a way the perceptible, and indeed preeminently the “seeable.” And it appears that this was recognized by the leading philosophers, which is why, in olden times, the Democritean ontology of “atoms and the void” was rejected by the major schools. What changes the picture in our day—and has given rise to endless confusion—is the fact that since the time of Newton we have been confronted by two very different and indeed conflicting ways of knowing; for in addition to the way of direct perception, the modus operandi of physics has confronted us with a strange new world: the physical, namely, as distinguished from the corporeal.

It is this fact that has been dramatized by Sir Arthur Eddington in his example of the “two tables”: the one we perceive in our daily life, and the other consisting “of atoms and the void.” Eddington’s mistake, however, was to suppose that the former is situated in the brain or imagination of the percipient, whereas the “molecular” is the one and only table that actually exists. Misled on the one hand by Cartesian bifurcation and on the other, it would seem, by a naively realist interpretation of the quantum world, he failed to recognize what is in a way self-evident: the fact, namely, that what we know answers to the modus operandi of the knowing. Thus, if we look upon the world “directly” by way of sense perception, we behold the familiar table (the one which supposedly does not exist), whereas if we look through the “lenses” of the physicist, we “see” the molecular. In a word: what you see depends on how you look.¹⁰

There is however a second point to be made: the fact, namely, that in light of quantum theory, the molecular table does not in truth exist as an entity! There is a fundamental asymmetry between the two aforesaid “ways of knowing”: for it happens that the modus operandi of the physicist is itself based, finally, upon sense perception: sooner or later it is necessary, after all, to discern at least a pointer on a scale or a spot on a photographic plate. It turns out, thus, that the way of direct perception holds primacy: that in a sense we know the physical by way of the corporeal—a fact which needs to be understood lest we mistake the so-called molecular table for a res extensa.¹¹  There is an epistemological asymmetry, thus, between the two ways of knowing which it behooves us to grasp: for it proves to be the key by which the enigma of the “two tables” is resolved.

We are not, however, obliged to reinvent the wheel; it is high time, rather, to avail ourselves of the authentic metaphysics to be found in the traditions worthy of respect. I will choose the Thomistic, in part because it connects directly with our question through its emphasis on sense perception, which it identifies as the primary means of human knowing. The fact, therefore, that the modus operandi of physics hinges upon sense perception puts us straightway on Thomistic ground. What then, Thomistically speaking, differentiates the corporeal domain—the world as known through sense perception—from the physical? The first thing a Thomist is prone to note is that physical entities are defined in exclusively quantitative terms, which is to say that the physical universe constitutes inherently a quantitative realm. To the Scholastic mind, this recalls the dictum “numerus stat ex parte materiae”: “number derives from the side of matter.” The allusion, clearly, is to hylomorphism, which conceives of corporeal entities as consisting of two ontological principles: morphe or form, plus materia or matter. The point is that neither materia nor forma exist by themselves: it “takes two to exist.” The fact, therefore, that “number derives from the side of materia” suggests that one of the two factors—forma namely—is missing in what we have termed the physical realm: it turns out that an ontological domain defined in purely quantitative terms is perforce sub-existential. And here, in brief, we have the resolution of the quantum enigma: a quantum particle, say, by virtue of its purely “quantitative” nature, is consequently situated “midway between being and nonbeing,” as Heisenberg has put it, and is in truth no more than an Aristotelian potentia. What “actualizes” such potentiae, moreover, is none other than the act of measurement, and it does thus actualize by contributing the ingredient of form. What on the other hand distinguishes the quantum realm itself from materia as such—termed prima materia—is the fact that it is endowed with a quantitative structure. The physical domain reduces thus to what is termed a materia secunda or “secondary” materia. It is interesting, furthermore, that St. Thomas speaks of a materia quantitate signata: a materia secunda, that is, which he characterizes as “marked by quantity.” For my part, I can hardly conceive of a more fitting metaphysical description of the physical universe.

What I wish now to convey is that these Thomistic considerations not only shed light on the nature of the quantum world, but in fact provide the key to a metaphysical comprehension of physics as such. They establish, first of all, the necessity of quantum mechanics as a rectification of Newtonian physics by the fact that the res extensae upon which Newtonian physics is based do not actually exist. It was thus foreseeable from the outset that as the operative conceptions of Newtonian physics sharpened and became ever more operational under the influence of such philosophical schools as logical positivism, a point would be reached at which the postulated res extensae dissolve, as it were, into the mist of the quantum realm. It thus becomes manifest that quantum mechanics is simply physics divested of its Cartesian illusions—simply, physics come into its own. The advent of quantum theory—or better said, the transition from classical to quantum physics—was thus predictable on metaphysical and indeed Scholastic grounds, based upon the modus operandi of physics as such.

It may be well to note at this juncture that a metaphysics is always in play: our choice lies between a true and a false metaphysical doctrine. And as we have seen, the Newtonian edifice had a metaphysics of its own—the Cartesian, namely—the hegemony of which, as we have noted as well, persists to the present day, notwithstanding the fact that this metaphysics flies in the face of quantum theory. One may ask oneself, thus, how it is possible to espouse a metaphysics at odds with a physics we know to be true. But whereas this is not possible so long as one understands the physics in question, it is if one doesn’t. It turns out, thus, that Richard Feynman was right: no one can “understand quantum theory” ontologically so long as he remains committed to the Cartesian Weltanschauung.

What is called for is a radically different metaphysics, and it will no doubt come as a surprise to many that such a doctrine is readily to be found in a culture we have maligned with gusto for a very long time. Following centuries of reproof on the subject of “exploded medieval superstitions,” it appears that the shoe is now actually on the other foot: for as we have come to see, even a cursory comprehension of Scholastic doctrine suffices to resolve the impasse which has stymied our top intellectuals since the advent of quantum theory.

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