The Multidimensional Spectrum of Imagination
Nigel J.T. Thomas
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Source : http://www.imagery-imagination.com/spectrum.htm
McGinn on the Discontinuity of Imagination and Perception
Colin McGinn's recent book on imagination, Mindsight (2004), is notable in that it succumbs neither to Romantic obscurantism about the imagination nor to its inverse, scientistic deflationism (although it does not directly confront either tradition). This is surprising in a way, because McGinn is well known for his "mysterianism" about consciousness. Although he believes that consciousness arises from the brain, he holds that how this can be so is likely to remain forever beyond the reach of our understanding (1999). Imagination and consciousness are closely intertwined concepts (Thomas, 2006), and mysterian attitudes towards imagination have long been with us. It was not only Romantic poets who regarded it as ineffable. Even Hume, that most sober of philosophers, called the imagination a "magical faculty," (1739 I.1.vii), and Kant, in similar vein, described it as depending upon "an art concealed in the depths of the human soul, whose real modes of activity nature is hardly likely ever to allow us to discover" (1781-7 A141-B181). However, there is no sign of mysterianism in Mindsight. McGinn clearly hopes for, and is seeking a basis for, a rational and scientific understanding of imagination. I do not think he succeeds: I shall argue below that he makes a number of significant false steps. However, his work does open up possibilities for useful discussion. In what follows, I will attempt to build upon McGinn's work, and to correct his more serious mistakes, in order to move forward his project of developing an understanding of the imagination that neither sanctifies nor trivializes it.
Unlike most analytical deflationists, but in common with virtually all pre-twentieth thinkers, including the Romantics (Warnock, 1976; White, 1990 pt. 1; Brann, 1991), McGinn sees mental imagery as central to the concept of imagination, and much of his book is in fact concerned with imagery. In his crucial first chapter, he focuses on the differences between mental images and percepts. Many writers about imagery have held some version of what we might call the "continuum theory". That is, they have regarded images and percepts as being varieties of the same species, differing in degree rather than in kind, and lying at opposite ends of a continuous spectrum with many varieties of imaginatively informed perception, such as seeing as, hallucination, and perceptual errors of various sorts, filling in the continuum between them. Some have defended this idea explicitly (e.g., Jastrow, 1899; Savage, 1975; Thomas, 1997); more often it is accepted implicitly, without real argument.
Indeed, the contemporary cognitive science of mental imagery is very largely predicated upon the truth of the continuum theory. Setting aside minor variants, there are currently three hotly contending candidate scientific theories of mental imagery (Morris & Hampson, 1983; Thomas, 1999a, 2008, 2009a). According to quasi-pictorial theory, visual percepts and visual mental images are both picture-like, two-dimensional patterns of excitation in a "visual buffer" in the brain (Kosslyn, 1994; Kosslyn, Thompson, & Ganis, 2006). According to description (or "propositional") theory, percepts and images are both descriptions of visual scenes, couched in the brain's inner "language of thought" (Pylyshyn, 1978, 1981, 2002, 2003). According to enactive theory (a.k.a. motor theory, perceptual cycle theory, role taking theory, etc.), the process of perception necessarily involves action (Neisser, 1976; Ballard, 1991; O'Regan & Noë, 2001; Noë, 2004), and both perceptual experiences and mental images are (or supervene upon) equivalent, but abortive and largely covert, perceptual action sequences (Neisser, 1976; Thomas, 1999a, 2009a,b; Bartolomeo, 2002; Blain, 2007).Although these three types of theory are in deep contention with one another in many respects, at both empirical and philosophical levels, all of them regard mental images as fundamentally akin to percepts. (Their differences are rooted in deeper differences over the nature of perception, mental representation, and conscious experience (Thomas, 2008, 2009a).) Thus they all depend upon the continuum theory. I do not know whether a theory of the nature and mechanisms of imagery that does not assume the continuum theory is really a coherent possibility; at any rate, no-one ever seems to have devised one.
McGinn, however, follows philosophers such as Reid (1764 II.5) and Sartre (1940), who reject the continuum theory, and draw a fundamental conceptual (and phenomenological) distinction between images and percepts (and, thus, imagination and perception). This distinction plays a large role throughout Mindsight. Although McGinn defends this view in considerably more detail than his predecessors ever did, and although his defense is lucid, insightful, and superficially persuasive, I believe that it fails, and, in fact, that we positively need the continuum theory if we not to fall back into mysterianism. It is not clear that we can even get a grip on the concept of mental imagery without recognizing its fundamental kinship with perceptual experience (see Thomas, 2008 §1.1, 2009a), and as we have just seen, without it we have no inkling of a scientific account of imagery. McGinn's arguments, however, are valuable, because, through exploring in detail how they fail, we should be able to deepen out understanding of the real relationship between perception and imagination.
McGinn initially approaches the issue via Hume's well known version of the continuum theory. Hume (1739 I.1.i) held that percepts and images (impressions andideas, in his terminology) differ only in their degree of "vivacity" (by which he is generally taken to have meant something like vividness). They differ in the "force and liveliness" with which they strike the mind. Like many commentators before him (e.g., Reid, 1764 II.5, VI.24; Savage, 1975; Warnock, 1976), McGinn has no difficulty in showing that this view (on any plausible interpretation of "vivacity") is seriously inadequate. After all (as Hume himself admits), it is perfectly possible, and not even particularly uncommon, for people to experience percepts that are far from being vivid, forceful or lively (think, for example, of a distant cry, barely heard over the noise of some loud hubbub). Likewise, imaginative experiences can occasionally be very vivid, forceful and lively without, thereby, tempting us to mistake them for percepts. Even if we do occasionally make that mistake, furthermore, it remains a mistake. Our imaginings do not become percepts just because they are forceful and lively enough to fool us; but Hume's account seems to entail that they should.
Having effectively demolished Hume's version of continuum theory (and thereby, he seems to think, all possible versions), McGinn goes on to list nine (not necessarily independent) respects in which, he thinks, imagery and perception really do differ:
1) Will: We can freely choose to imagine pretty much anything we want, at any time, but we can perceive only what is actually now before us (p. 12ff);
2) Observation: Perception can bring us new information about out current environment, but imagination cannot (p. 17ff);
3) Visual field: Our eyes can only take in things within a physiologically fixed angular field of view, and the things we see must always appear at some particular location in this visual field. Imagination, by contrast, suffers from no such limitations.(pp. 22ff);
4) Saturation: McGinn is aware of the fallacy of the hoary argument that mental images can be indeterminate in a way that percepts cannot. However, he defends the related view that perceptual experiences are always "saturated" (i.e., some quality is always manifested at every point in the visual field), whereas images are typically unsaturated or "gappy": an object, such as a face, may be visualized without every detail, every shade of color at every point, being specified (p. 25f);
5) Attention: "I can pay attention to what I am seeing or I can fail to pay attention to it; but I do not have this choice in the case of images: here I must pay attention in order to be imaging at all. . . . [I]mages necessarily involve attentive intentionality . . . . [O]ne has to attend to the object of the image in order for the image to exist" (p. 26ff );
6) Absence: If we say that we perceive something, this implies that the something is really there in the world, present to our senses. By contrast, if we say that we imagine something, this implies that it is not there, not present to our senses (p. 29f);
7) Recognition: One knows the identity of the object of one's imagining simply in virtue of the fact that one has chosen to imagine that thing. No further act of recognition is needed in order to identify it. By contrast, perceiving what something is does require an act of recognition, because the identity of the object is determined not by the will, but by how the world is (p. 30f );
8) Thought: Although you can perfectly well be seeing X and, simultaneously be thinking of Y, you cannot be imagining X and simultaneously be thinking of Y. (p. 32);
9) Occlusion: Unlike real things, imaginary things do not block or occlude the visual scene. If there is a tree in front of us, we will not be able to see whatever might be hiding behind it, but if we imagine a tree in front of us, however vivid it may be it will not hide anything that is really there (p. 32f f).
I think most of what McGinn says about imagery here, and some of what he says about perception, is true. Imagery and perception do differ in most of these ways. I shall argue, however, that, like Hume's "vivacity," these differences are all best construed as differences of degree (or consequences of underlying differences of degree). Thus, the failure of Hume's simplistic, one-dimensional, "vivacity" based version of the continuum view is no ground for rejecting the view out of hand.
Nevertheless, McGinn's analysis does suggest that there are several distinct ways in which imagery and perception differ, and although not all these ways are necessarily independent of one another, this still implies that our continuum, or spectrum, is likely to be a multidimensional one. (And with that acknowledged, there will no harm in throwing vividness or vivacity back into the mix, as one of these dimensions, so long as we are not tempted, like Hume, to privilege it over the others.) As McGinn himself points out, there is a whole range of types of experience (he classifies most of them as forms of "imaginative seeing") that are like perception in some ways and like imagery in others. If any particular such experience happens to fall well towards the perception end of the spectrum on a majority of these dimensions of difference, and only towards the imagery end, or towards the middle, on a lesser number, we might be inclined to classify it as a somewhat atypical case of perception. If the reverse is true we might be inclined to think of it a slightly aberrant example of imagination. Other more mixed cases may call for other terms: illusion, hallucination, pseudohallucination, phantasm, daydream, figment, fancy, visual ambiguity, misrecognition, pareidolia, hypnagogic image, etc. Both ordinary and technical language provide a rich, but unsystematic, vocabulary for talking about such things. One of the attractions of the multidimensional spectrum view is that it might provide the basis for a more systematic way of organizing our understanding of them. We might hope ultimately to be able to map the various types of imaginative and perceptual phenomena as regions within a unified multi-dimensional phase space. Before that project can begin, however, it must be shown that what McGinn thinks are absolute differences in kind, qualitative differences, are all (or are all reducible to) quantitative differences of degree.
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