The Multidimensional Spectrum of Imagination
Nigel J.T. Thomas
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Source : http://www.imagery-imagination.com/spectrum.htm
Reestablishing Continuity: 1. The Will
Because of the ways in which the issues are interrelated, in what follows I will not deal with McGinn's points of difference strictly in the order in which he introduces them (i.e., as listed above). Instead, each time I touch on one of these points, I will mention it in bold type, using the name it has been given in the bolded headings of the above list (which correspond quite closely to McGinn's own section headings).
Nevertheless, we may conveniently begin at the beginning, by considering will. On the one hand, this may be the criterion most likely to resonate with other philosophers, because far more influential philosophers than McGinn, notably Sartre (1940 p. 18) and Wittgenstein (1967 §§629, 633), have made similar points before. On the other hand, it is not difficult to make a prima facie case that it marks a difference of degree rather than kind. Although it is true that we do typically have considerable voluntary control over our imagery, this is by no means absolute, and varies in degree from case to case: we may want to imagine some familiar person's face, but be quite unable to call it to mind, and even when we can form an image of something, it is often very difficult either to visualize much detail, or to maintain the image in consciousness for more than a fleeting moment. By the same token, most people have had the experience of some apparently random image popping unbidden into consciousness, or of being unable to dismiss some annoying or disturbing image (perhaps of some gruesome or disgusting sight) from their mind. This does not just apply to visual images, either: most of us know what it is get a song or a snatch of music stuck, infuriatingly, in our heads.
Hallucinations might also very plausibly be taken to be examples of mental images that have thoroughly escaped the control of the will, and, as we will see later on, they have been so taken by many of the clinicians and scientists who have studied them. (This does not accord with McGinn's conception of hallucination, but, as we shall also see, that conception is badly confused.)
Perception, in turn, is not so far beyond voluntary control as McGinn wants to imply. Although the content of visual experience is, at any one time, certainly strongly constrained by what is within range of the eyes, we nevertheless have a considerable degree of voluntary control over what we actually see. Something may be there in front of you, but, if you don't want to see it, it is easy enough to shut your eyes, or turn them away; or if you do want to see what is not quite in front of you, it usually takes no great effort to turn your eyes or move your body toward it.
Ichikawa has recently attempted to defend McGinn's view about will from objections of this sort. He concedes that we cannot always control our imagery as well as we would like. However, he insists (rightly, I think), that, whether we succeed or no, we can always try to control our imagery, try to form a particular image, or to banish one from consciousness. By contrast, he thinks, it does not even make sense to try to exert an equivalent sort of control over perception: "The instruction, ‘stop having the auditory experience of my voice,’ or ‘start having the visual experience as of a red square’ is a confused one" (Ichikawa, 2009 p. 107).
Those instructions, however, do not, in fact, leave me confused. It seems to me that not only could I try to follow them, but very often I could quite easily succeed. If I want to stop experiencing someone's voice, can I not stick my fingers in my ears and hum, or perhaps leave the room? As for seeing a red square, I believe I have a square red box around here somewhere that used to hold floppy discs. . . . Let me just take a moment to find it . . . and hold it up to look at. . . . There! Done!
Of course, these performances will not satisfy Ichikawa. He has already (albeit offhandedly) dismissed the suggestion that we can voluntarily change what we see by redirecting our attention elsewhere by saying that this only amounts to "indirect" control over our perceptual experience (2009 p. 107). Presumably this is meant to contrast with the direct (though imperfect) control we apparently have over our imagery, and, if merely shifting attention is sufficient for indirectness, presumably he would think that performances like leaving the room or finding and holding up a red box are profoundly indirect ways of affecting one's perceptual experience.
What, however, is the basis for this direct/indirect distinction? Ichikawa does not say, but so far as I can see, the only plausible surmise is that (for him – and perhaps implicitly for McGinn, Sartre, and Wittgenstein too) direct control of our experience is that which can be accomplished through purely mental acts, whereas when such control involves actual bodily movements (even small ones, like turning the eyes in their sockets, or lowering their lids) then it is merely indirect.
There are at least two sorts of good reasons to reject this distinction (or, rather, to reject the idea that it is a difference in kind rather than of degree). First of all, unless we are to embrace metaphysical mind-body dualism (I doubt that Ichikawa wants to do that, and I know McGinn does not), it is not at all clear that any sharp and principled distinction can be drawn between mental acts and bodily acts. On the one hand, both, being acts, bear intentionality, so that will not serve to distinguish between them. On the other hand, from a materialistic point of view, why should we draw a sharp, ontologically significant distinction between those movements of ions and molecules through and around membranes that constitute neural activity in the brain, and the very similar electrochemical processes that constitute both signals in the peripheral motor nerves and the events within the muscle fibers that cause them to contract? Perhaps bodily acts (if we take them to consist of the relevant muscle contractions plus the central and peripheral neural activity that brings them about) typically use up more energy than purely mental acts, but that is a quantitative and not a qualitative difference.
Quite apart from this, however, Ichikawa seems to be assuming that changing what you see always depends upon actual bodily movement (such as turning the eyes or the head), whereas changing what you imagine never does. He is mistaken on both counts.
First of all, we can, to a degree, shift the direction of our visual attention without moving our bodies (or our eyes) in any relevant way (Posner, 1980). There is some reason to believe that such "fixation shifts," as they are called, could be enough to make an object appear or disappear from visual consciousness (Mack & Rock, 1998); certainly they can have profound effects on what it is that we think we are seeing (Tsal & Kolbet, 1985).
Even more significantly, however, there is now a considerable amount of evidence, from a range of experiments, to show that unconscious eye movements are directly involved in mental imagery. A variety of experiments have revealed that, when people form a visual mental image, they spontaneously tend to move their eyes in a spatiotemporal pattern that parallels the distinctive eye-movement pattern that they would have used in actually viewing the object or scene being imagined (Brandt & Stark, 1997; Spivey & Geng, 2001; Johansson et al., 2006). If they deliberately refrain from making such movements, their imagery is degraded (Laeng & Teodorescu, 2002). Thus (in many, and perhaps most, cases), if someone wants to change what they are visually imagining, they will have to change the way they are moving their eyes. Indeed, although Ichikawa talks of banishing a mental image as if it were an effortless, purely mental act, probably the easiest way to actually get rid of an intrusive, unwanted image is to move the eyes about deliberately, so as to disrupt the spontaneous but unconscious eye movement pattern that is sustaining it (Antrobus et al., 1964; Andrade et al., 1997; Barrowcliff et al., 2004).
All in all, then, Ichikawa's sharp, qualitative distinction between direct and indirect control over one's own experience cannot be sustained, and thus he and McGinn fail in their attempt to establish that the criterion of susceptibility to the will marks a qualitative difference between imagery and perception. I am not denying that it may usually be noticeably easier to control what we imagine than to control what we see, or even that, sometimes, we might use our sense of how, and to what degree, we are controlling an experience to ascertain whether it is real or imaginary (as Hume apparently thought we might use degrees of vividness), but this is not the sharp difference in kind that McGinn (and Ichikawa, and Sartre, and perhaps Wittgenstein) wants.
Of Passive Perception, Visual Impressions, Retinal Images, and Eye Movements
The points I have made about changing your perceptual experience through bodily movement, through turning your eyes in a different direction, banal though they may seem, touch, I think, on what may be the real foundation for the belief that imagination is fundamentally different from perception. Those who hold this view – certainly those whose defense of it we are considering here: Sartre, McGinn, Ichikawa – believe that imagination is inherently active, that imagining is something we do. That much is fairly uncontroversial, and I certainly have no quarrel with it. However, they think of perception, and visual perception in particular, as in its deepest essencepassive.
Sartre, indeed, makes this point quite explicit (1940 ch. 1 §5), and Ichikawa (2009 p. 107) quotes the relevant passage approvingly, so we may take it that he agrees. McGinn is less direct, but, once one is on the alert to the issue, his passive view of perception is obvious enough, perhaps most clearly when he discusses how he thinks imagination and perception can be differentiated in terms of their relationships with attention and thought (matters to which we shall return). In effect, all these authors rest their arguments upon the assumption that we do not really need to do anything in order to see: that if something is illuminated and before our opened eyes, if it projects an optical image onto the retina (and the relevant nerve pathways are intact, etc.), then we see it, quite regardless of whether we look at it, or attend to it. From this perspective, turning the eyes is not really part of the process of seeing at all; it is something that intervenes between actual instances of seeing. Real seeing occurs when the eye is still enough to receive a nice, steady image on the retina.
An alternative, radically active conception of vision (and perception in general) has recently been strongly advocated by Noë and others (2004; O'Regan & Noë, 2001; Thomas, 1999a). However, I do not believe my current argument depends upon a full acceptance of this viewpoint. For present purposes, I only need to establish that eye movements play an essential, rather than merely incidental, role in the normal process of seeing, and that the radically passive conception of vision, even though implicit acceptance of it is so widespread, is not a conceptual or empirical inevitability. It is neither the inevitable verdict of science, nor a deliverance of some timeless philosophical intuition. Rather, it has become entrenched in modern educated common sense for quite contingent historical reasons.
One source of this passive conception of vision, is the tempting analogy that has often been drawn between the process of seeing and the process of making an impression in wax. This analogy was perhaps first used by Democritus (Stratton, 1917 p. 111), and Aristotle took it up in order to explain how it might be possible for the soul to receive the form of a visible object without its actual matter entering into us (De Anima 424a 17ff). The soft wax, of course, represents the mind as it waits, passively, to be imprinted by the incoming sensory form.[9] As a metaphor for perception, the word "impression" is still very much with us, having been revived in the 17th century by Hobbes, amongst others, and then becoming central to Hume's philosophy. The fact that not only Hume himself, but most of his readers, even today, seem to regard this as an entirely innocuous, untendentious metaphor, is an index of how deeply the passive view of perception in general, and vision in particular, has become embedded in modern, educated common sense.
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