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(Extracted from Lehar (2000) The Function of Conscious Experience)
The question of the epistemology of conscious experience has a long and colorful history in psychology and philosophy. The epistemological question is intimately related to the issue of mind-body dualism, because all of the problems inherent in the na´ve realist view simply evaporate if we allow for the existence of an immaterial soul, whose function is not entirely dependent on the mechanical functioning of the physical brain. For in visual perception we do indeed feel as if our consciousness extends outwards beyond the confines of our physical head, to make direct sensory contact with remote objects in the world. But while the external nature of perception has been recognized into ancient times, so too has the causal role of the sensory organs in perception, for the world goes dark when we close our eyes, and disappears altogether when we lose our eyes. We have therefore two fundamental and apparently contradictory observations on the nature of vision, one that appears to lead inwards from the world through the eye to the brain as revealed by physiology, while the other appears to lead outward from the mind to the external visual world as revealed by phenomenology. With the rise of the materialistic world view ushered in by Newton's mechanical universe, there has been ever increasing pressure to formulate a materialistic explanation of the mystery of visual consciousness. As we review the history of this problem, a gradual progression is observed, as ever more of the properties of the phenomenal world, initially assumed to be identical to the external world, are attributed instead to processes internal to the brain and body. This leaves the phenomenal portions of the external world in a peculiar kind of limbo, being observed external to the body while being attributed to processes within the body. The ultimate solution to this paradox is only to be found by a complete indirect realist inversion, whereby everything that appears to be external is finally attributed unambiguously to internal processes in the brain, a view which forever closes the na´ve window of direct observation onto the external world.
The first stage of the epistemological inversion was proposed by Descartes. To the modern reader Descartes' view is remarkable in its dualism, i.e. its continued commitment to the immaterial soul of ancient religion. But to the philosophers of his day, the most remarkable aspect of the Cartesian view was how much of the perceptual process he attributed to the physical body, and how far the immaterial soul had retreated within it. For Descartes proposed that all sensory information is transmitted by the nerves to a central "theatre", where the soul makes contact with the physical body, a mind / body interface which Descartes located in the pineal gland. The prevailing view at the time was that the soul extended throughout the body and beyond, and this accounted for the external nature of perception. (Pastore 1971, p. 19) Descartes' rejection of this thesis was based on physiological grounds. For anatomy reveals the sensory organs connected to the brain by nerves, which suggests a propagation of sensory information inwards from the external world to the brain. But the full implication of Descartes theory would have been that the world we see around us is the picture in the pineal gland projected by the nervous system to the soul, for now the soul is shut in to the physical head, and can only see outwards indirectly by way of the senses. However Descartes was not prepared to accept the full implications of his own theory, so he appealed to the mystery of the soul to account for the external nature of perception, proposing that as the soul receives the sensory signals at the pineal gland, it instantaneously becomes aware of the external objects which are the ultimate source of the sensory signals. The role of the sensory organs is thereby somewhat ambiguous, being required to transmit sensory information from the world to the soul, but the soul does not even "see" this internal picture, but instead sees the world itself directly.
Subsequent explanations of the epistemological question were equally confused and self-contradictory. Malebranche (1674) proposed that sensory qualities, such as color, taste, and sounds, are not part of the external object but are internal phenomenal properties. The mind "becomes colored" when we view a colored object, although the object on which that color is perceived is not an internal replica, but is seen directly in the world where it lies. A perceived object therefore is partially an internal and partially an external phenomenon, with shape and volume existing out in the external world itself, but the color clothing the object being something in the mind. John Locke (1690) took the epistemological inversion one step farther to propose that even shape and volume were sensory properties, and therefore they too, like color, taste, and sound are properties of the mind rather than of the world itself. However Locke retained a residual aspect of direct perception in his distinction between the primary and secondary qualities of perception. The primary qualities, which include shape, size, and number, are, he claimed, a veridical representation of the actual properties of the objects themselves, while the secondary qualities such as color, smell, taste, warmth or coldness, or pain, are also produced by stimulation of sense but they have no resemblance to the corresponding qualities in the objects. (Pastore 1971, p. 64-66) The isolation of the soul from direct contact with the external world led Bishop Berkeley to question the very existence of the external world, for since we cannot see it directly, how can we know that it even exists? Berkeley therefore professed a form of idealism, whereby mind is all that really exists, as captured by Berkeley's dictum that "to be is to be perceived." As long as the choice is restricted to epistemological monist alternatives, the choice is between two incredible possibilities, either naive realism or idealism.
Immanuel Kant was the first to propose the full epistemological inversion. Kant proposed that there are in fact two worlds of reality, the phenomenal world of conscious experience and the nouminal world of objective external reality. The only way that we can observe the nouminal world is by its effects on the phenomenal world. But Kant's epistemology was confused by his acceptance of Berkeley's idealism, whereby the external world is not the material world familiar to modern science, but is itself a world of mind, although it is the mind of God, and thereby external to the mind of the individual percipient. But appeals to God and to the immaterial soul are ultimately unsatisfactory for a scientific theory because spiritual entities are in principle beyond the bounds of scientific investigation. Therefore the modern epistemological debate only began in earnest after the materialistic view of mind had been generally accepted, following the French materialists La Mettrie (1748) and Cabanis (1802) (see Boring 1950, p. 212-216) who first extended to man Descartes' notion that animals are automata.
The followers of Kant abandoned his epistemological dualism, and focused instead on Kant's idealism, claiming that mind is all that is knowable to man. This unfettered idealism eventually triggered a realist backlash by the American realist, or neo-realist philosophers (Holt et al. 1912) who professed what is plainly evident to the common man, that the external world is knowable through consciousness. But the neo-realists also advocated an epistemological monism whereby the world observed in conscious experience is the external world itself, and the epistemological debate had gone full circle back to the naive realism familiar to the common man. For the neo-realists claimed that even the secondary qualities such as color, smell, and taste, are objective properties of the external objects themselves, and are observed out in the external world, superimposed on the external objects to which they belong. But a naive realist philosophy cannot survive long against the obvious objections, and once again the same progression was replayed as one by one, ever more of the properties of the external world of perception were attributed instead to processes internal to the brain and body.
A more sophisticated epistemology was offered by the subsequent critical realist movement (Sellars 1916, Russell 1921, Broad 1925, Drake et al. 1920) who, like Malebranche and Locke, claimed that some aspects of the perceived object such as its color are in fact subjective and inhere in the mind, while other aspects such as its shape are properties of the objects themselves, and are observed directly out in the world on the objects themselves. But this explanation, which is intermediate between epistemological monism and dualism, led to the same kind of confusions as its earlier incarnation under Malebranche and Locke. For the perceived shape and perceived color appear superimposed in the same apparently external space, although one is supposedly a property of the mind which is presumably in the brain, whereas the other is a property of the external world which is outside the brain. The critical realists were vaguely aware of some kind of difficulty here, as they spent considerable effort agonizing over this muddled concept. For example Sellars (1916 p. 58) argued that "if realism is to be saved, it must disembarrass itself of its immediatism, i.e. the physical object can no longer be regarded as immediately present in perception." This statement is consistent with the epistemological dualism of Kant. However later in the same book Sellars (1916 p. 244) argues that "consciousness is not extended after the manner of a physical thing for the very simple reason that it is not a physical thing. Let all this be granted; yet in a very real sense consciousness is extended. As a variant of the brain it is in the brain, not as an ivory sphere is encapsulated in another in those curious products of Chinese patience which we see in museums, but in a unique way which it requires reflection to make clear." But no amount of reflection can clear up this mess, as seen in Sellars' conclusion (p. 246) that "Consciousness in the brain is not the relation of one thing to another, but the immanence of that part of reality which is our changing field of experience to the rest of the same existential part of the physical world. Unfortunately, there is no adequate word to express what we think." The obvious confusion in these statements about the relation of mind to brain is a direct consequence of a confused epistemology whereby the mind is in the brain, and yet at the same time it is somehow not in the brain.
Even more problematic was the question of perceived shape. For this supposedly objective property of external objects nevertheless has a subjective aspect due to perspective. For example a penny viewed in perspective appears subjectively as an ellipse, and the aspect ratio of that elliptical percept depends on the angle from which the penny is viewed, so different viewers of the same object see it in different shapes. The critical realists offered all kinds of improbable explanations to account for this troublesome aspect of perception. One solution was the concept of sense data, or sensa, whereby one object can produce a multitude of different sensa in different observers. (Broad 1925, p. 170 - 180) The sense data are neither physical nor mental, but "particular existents of a peculiar kind; they are not physical, ... and there is no reason to suppose that they are either states of mind or existentially mind-dependent. In having spatial characteristics ... they resemble physical objects ... but in their privacy and their dependence on the body ... of the observer they are more like mental states." (Broad 1925, p. 181) Bertrand Russell (1921, p. 97- 98) made the most concerted effort to formulate the concept of sense data as independent of the individual observer by suggesting that every possible sensum exists as a potential perceptual experience as if there were a subject there to perceive it. For example when viewed face-on, a penny projects a circular aspect whose size diminishes with distance from the penny, while when viewed edge-on the penny projects a linear or rectangular aspect whose length diminishes with viewing distance, and intermediate to the face- on and edge-on views are an infinite set of elliptical aspects of that same penny through the full range from linear to circular, and through a range of sizes, depending on viewing angle and distance. All of these sensa, according to Russell, are objective external existents which are part of the penny whether it is being viewed by a percipient or not, and that is how different observers can see different aspects of thesame objective entity. The whole set of these sensa are to be taken as actually being the perceived penny, which is itself neutral between different observers. Curiously, since the penny cannot be viewed from inside its own volume, Russell proposed that the sense-data which are the penny do not extend to within its own volume, so the penny exists everywhere in space except at that location where common sense would indicate it to be. Again, the ineffable relation between the object and its infinite set of sensa follows directly from the epistemological confusion whereby the sensa are both in the brain and subjective, and yet at the same time they are out in the external world and somehow objective.
The critical realists all agreed on the fact that the sense data are independent of the object of perception itself. However the question of whether the sense data are part of the mind, or whether they are aspects of the external object is one on which critical realists differed in subtle ways. In a book on critical realism by a consortium of authors (Drake et al. 1920) Lovejoy, Pratt, and Sellars claim that the sensa are completely "the character of the mental existent ... although its existence is not given" whatever that might possibly mean, while Drake, Rogers, Santayana, and Strong agree that the data are characteristic of the apprehended object, although "the datum is, qua datum, a mere essence, an inputed but not necessarily actual existent. It may or may not have existence." (p. 20-21 footnote), whatever that might possibly mean! So the critical realists solved the problem of sense-data by defining a unique kind of existent which may either be part of the external object, or of the internal mental state, but in any case it has a status of quasi-existence which supposedly escapes the problems inherent in identifying it explicitly as either an external or internal entity. Epistemological confusion inevitably leads to a confused philosophy.
Bertrand Russell, originally himself a critical realist, eventually discovered the resolution to this quandary with a realist version of Kant's epistemological dualism. What finally convinced Russell was consideration of the causal chain of vision. Light from an object in the world enters the eye, where it is transduced to a neural signal in the optic nerve, from whence it is eventually transformed into a pattern of activation in the visual cortex. There are two aspects of that perceptual activity, an electrophysiological aspect measurable by cortical electrodes, and a phenomenal or experiential aspect in the form of the percept itself. But the two are different manifestations of the same underlying structure, and therefore if the first is located within the physical brain, then the second must also be in the brain. (Russell 1927 p. 137-143) Russell observed that a potent source of confusion in this matter is a confusion of physical space with perceptual space. For although our percept of the external world appears external to our head, it is not external to our true physical head, but only to our perceptual head in perceptual space. All of our perceptual space, including the externally perceived world, is inside our physical head in physical space. (Russell 1927) This explanation of perception finally resolved all of the epistemological problems inherent in naive realism and in idealism without resort to any supernatural gods or mystical souls. It accounts for the fact that the perceived world appears external although we know it to be internal, by the fact that the external world of perception is internal to our physical brain. It accounts for the realism known to common sense, by the fact that the phenomenal world, while truly internal and shut-in within the physical brain, nevertheless accurately reflects certain geometrical aspects of the external world, which is thereby knowable indirectly through its perceptual replica. It accounts for the fact that different individuals each have their own unique perspective on a commonly viewed object by the fact that each individual percipient has his own perceptual copy of the commonly viewed object. And it does away with the incredible proliferation of infinite sets of different perspectives for every object in the world, as well as with notions of phenomenal sense data which are experienced but which do not or may not actually exist. Bertrand Russell's epistemological dualism and causal theory of perception should therefore have resolved the epistemological question once and for all. But curiously it did not, and the reason why it has failed to do so is almost as interesting and significant as the epistemological question itself.
The epistemological debate highlights the very powerful human inclination to favor a naive realist view. After all we are all born naive realists, and only a few in each generation ever come to see through the grand illusion of conscious experience. Russell's causal theory of perception has never been refuted, and yet it continues to be simply ignored or misunderstood, although each of the alternatives to epistemological dualism have been repeatedly shown to be fatally flawed. The chief problem is that indirect realism seems so incredible that it is most often not even considered as a serious alternative. As Russell himself said, "Perhaps there is nothing so difficult for the imagination as to teach it to feel about space as modern science compels us to think ... This question is very important, and must be understood if metaphysics is ever to be got straight. The traditional dualism of mind and matter, which I regard as mistaken, is intimately connected with confusions on this point. So long as we adhere to the conventional notions of mind and matter, we are condemned to a view of perception which is miraculous. We suppose that a physical process starts from a visible object, travels to the eye, there changes into another physical process, causes yet another physical process in the optic nerve, finally produces some effect in the brain, simultaneously with which we see the object from which the process started, the seeing being something 'mental', totally different in character from the physical processes which precede and accompany it. This view is so queer that metaphysicians have invented all sorts of theories designed to substitute something less incredible. But nobody notices an elementary confusion". (Russell 1927, p. 137 - 143)
Lovejoy's (1930 p. 227-249) response to Russell's epistemological dualism is typical. Lovejoy does not argue on logical grounds that percepts cannot be in our heads, but argues instead that there are alternative explanations which, however improbable, at least leave the door of doubt open a tiny crack. One such possibility is a projection theory, that the patterns of electrochemical activity in our brain get somehow projected back out into the world. Another possibility is that although perceived objects are not in physical space, "it does not follow that they are in our heads; they might ... be neither in our heads nor where the 'scientific objects' are, but in some other situation in physical space." (Lovejoy 1930 p. 228) His third argument is that it has never been proven that `being known' is necessarily equivalent to `being in our heads'; and finally Lovejoy argues that the question whether percepts are in our heads is not the same as the question whether perceiving and awareness are physical processes, and that he rejects the former but accepts the latter. What is curious about these arguments is that Lovejoy feels no need to commit to any one of his proposed alternatives. Lovejoy does not profess a projection theory, but merely argues that it is not self-evident that it is untrue. If percepts are not in our heads, Lovejoy does not propose where else they might be. He does not explain how anything can be known that is not explicitly represented in our physical brain, nor how the physical processes underlying perception and consciousness could be anywhere other than in our brain. This therefore is not a refutation of Russell's causal theory of perception, but merely an expression of Lovejoy's opinion that Russell's theory seems so incredible to him, as to be on a par with those other incredible hypotheses.
Contemporaneous with Bertrand Russell in philosophy, the Gestalt movement in psychology was arriving independently at the same epistemological conclusion. Although initially Gestalt theory began as a theory of perception, Wertheimer clearly recognized the epistemological issue at the heart of the matter, and Wolfgang K÷hler and Kurt Koffka motivated their presentation of Gestalt theory explicitly on epistemological dualist grounds. Curiously the Gestaltists made no reference to Kant as the originator of this idea, possibly because of the confusion caused by his idealist position, nor to Bertrand Russell's parallel arguments in the philosophical world. One of the most controversial and pivotal aspects of Gestalt theory is Wertheimer's principle of isomorphism, elaborated by K÷hler (1924) as the hypothesis that every perceptual experience is "not only blindly coupled to its corresponding physiological processes, but is akin to it in essential structural properties." This theory is a direct consequence of the indirect realist foundations of Gestalt theory, whereby phenomenal experience is a direct manifestation of neurophysiological processes in our physical brain, and therefore it cannot help but be similar in structure, since they are identical in ontology.
But despite the clear and cogent arguments made by the Gestaltists in defense of indirect realism, this idea was never widely accepted, although it was rarely challenged directly. It was however challenged by J. J. Gibson, who is one of the few people to explicitly defend a na´ve realist view of perception. But Gibson's challenge did more to highlight the shortcomings of direct realism than of representationalism, because Gibson was forced to make all kinds of implausible assumptions about the perceptual process in defense of his na´ve realist position. Gibson denied, for example, that the retinal image is anything like an image, and he denied the general materialist view that the sensory organs transmit sensory information into the brain, where neurophysiological processes compute a perceptual representation of the external world. Instead Gibson suggested that perception occurs somehow out in the world itself, rather than in the physical brain. Exactly how this occurs, or what this actually means however, he could never explain to any satisfaction. Once again Gibson demonstrates how a confused epistemology leads to a confused psychology. Significantly, neither Gibson nor anybody else has ever shown indirect realism to be untenable, only that it seems (to them) incredible. But despite the absence of challenge to the Gestalt arguments for indirect perception, and despite Gibson's failure to provide a plausible direct perception alternative, the issue has simply dropped out of the collective consciousness, and na´ve realism once again by default rules the day in psychology and philosophy.
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