An Introduction to the Science and Philosophy of Mental Imagery
Nigel J.T. Thomas
Page 3
Source: http://www.imagery-imagination.com/mipia.htm
3. Key philosophical issues
§3.1 Meanings of "imagery"
Few discussions of imagery draw a clear distinction between the claim that people have quasi-visual experiences and the claim that such experiences are caused by the presence of picture-like objects in the mind. In practice, in the literature, "mental imagery" (or "mental images") can mean any or all of at least three things:
[1] Quasi-perceptual conscious experience per se;
[2] Picture-like representations in the mind and/or brain that may be experienced as [1];
[3] Any inner representations whatsoever that may be experienced as [1].
Picture theory is so entrenched in our language and our "folk psychology" that it is only too easy to assume that when people say "imagery" they mean [2]. Far too many confident arguments about what imagery can or cannot do depend on an (often unacknowledged) assumption of pictorialism (Thomas, 1989, 1997a, 1997b).
Block (1981a-Introduction) argues that some confusions could be avoided, without prejudging the "analog-propositional" issue, if we agreed to define "imagery" as [3]. However, one can perfectly consistently maintain the reality, and perhaps even the cognitive importance, of imagery in sense [1] whilst denying the existence not only of [2] (with description theorists like Pylyshyn or Slezak), but even of [2] and [3] (with Ryle, Sartre, or Thomas: see §1.3 and §2.3 above). Defining "imagery" as [1] (as we did initially) seems to beg the fewest questions.
§3.2 Imagery, intentionality, and mental representation
Nearly all philosophers accept that imagery has intentionality: the characteristically mental property of being of, about, or directed at some object (real or imaginary). In this regard, mental imagery proper may be distinguished from superficially similar but non-intentional phenomena such as afterimages and phosphenes. This philosophical concept of intentionality is only distantly related to the notion of doing an action intentionally (i.e. on purpose), but it is very closely related to the notion of meaningful representation. To say that an image is of a lion is to say that it represents a lion. But how is it possible for anything to have this property of intentionality, this power of being able to represent things? This is perhaps the most fundamental problem in the philosophy of cognition, and the answer we give to it will profoundly affect what sorts of cognitive theories we think are workable.
Most philosophers before the 20th century held that mental images formed the basis of the mind's power to represent things, and probably assumed that images represent their objects because they resemble them: an image of a lion, like a photograph of one, looks like a lion. However, consider two photographs of Leo. Each photo resembles the other more than either resemble the lion (both photos are small, rectangular pieces of card, similarly marked, and neither is carnivorous or furry), yet we would normally want to say that they represent Leo, and not that they represent each other. Of course, a photograph of Leo does resemble him, when the right aspects of resemblance are considered, but in this regard Leo equally resembles the photograph. We are unlikely, however, to want to say that he represents it. In order for resemblance to play a role in representation, the relevant aspects of resemblance have to be recognized, and the resembling object has to be used (or, at least, taken) as a representation. But surely, before a cognitive system can recognize or use the relevant aspects of resemblance between a photograph (or an inner quasi-picture) and an object (or a percept), it must already be able to represent the picture and its object, and their various features, to itself. The mind's power to recognize resemblance seemingly depends on its power to represent things, rather than vice-versa.
From related arguments, Fodor (1975) concludes (with the analytical philosophy mainstream) that mental images do not possess their intentionality intrinsically. Rather, they derive it from that of another, supposedly more fundamental, form of representation. For Fodor, an image (a quasi-picture, he assumes) of a lion represents a lion not because it resembles a lion, but, in effect, because our minds attach a mentalese caption to it saying "LION". It is not that the resemblance is not real, or cognitively useful, but that (contrary to traditional views) mentalese, not imagery, is the fundamental form of representation and the source of intentionality. This line is apparently accepted by Tye (1991) in his philosophical exegesis and defense of quasi-pictorialism. Of course, those like Pylyshyn, who hold that imagery consists of mentalese, also ground the intentionality of imagery in that of mentalese.
It is worth noting, however, that, despite strenuous philosophical efforts over the last quarter century, no generally acceptable theory of the source of the representational power of mentalese is forthcoming, and, indeed, none may be possible (Horst, 1996; Cummins, 1997). We might do without the rather extravagant hypothesis of mentalese if the intentionality of imagery could be derived from that of ordinary spoken language (Kaufmann, 1980). However, this would seemingly require an account of the intentionality of ordinary language that avoids reliance upon any appeal to the intentionality of the mental. The prospects for that seem poor. It would also apparently imply that animals and babies have no intentionality: that, in effect, they have no minds.
But just because the resemblance theory of representation fails, it does not necessarily follow that the intentionality of imagery is not intrinsic. After all, resemblance theory was only ever intended to apply to pictorial theories of imagery. If imagery is conceived of as a form of directed perceptual activity (see §2.3), rather than as an inner representation, perhaps its intentionality might be understood as rooted in the inherent goal directedness of action. Such an approach still awaits detailed articulation, however, and would presumably require an account of the intentionality of action that did not root that in the intentionality of representations.
§3.3 Imagery and consciousness
According to most cognitive scientists, mental images are mental representations (pictorial or otherwise) that have their existence as brain states. How could we be conscious of such things (as we clearly can be conscious of imagery)? It seems unlikely to be in virtue of any intrinsic characteristic of the relevant brain state, for brain states are nothing but patterns of excitation of neurons, and excitation of neurons is nothing more than electro-chemistry: the movements of certain molecules and ions, polarization and depolarization of membranes, and so on; quite ordinary physical processes that go on outside of brains, and even, quite frequently, within brains, without producing consciousness.
Perhaps, then, such representations are not conscious because of any properties they have intrinsically, but, rather, we are conscious of them inasmuch as our minds access and extract information from them. This is a quite traditional idea embodied in the idiom of "the mind's eye", and it found its clearest philosophical expression in Descartes' (1664) account of imagery, wherein the image is presented as a small physical picture formed deep within the brain (at the pineal gland), from where the immaterial conscious soul is able to apprehend it directly. Nearly all cognitive scientists (and contemporary philosophers) firmly reject such explanatory invocations of the supernatural. Nevertheless, Kosslyn, the leading contemporary quasi-pictorialist (§2.2), sometimes writes of a "functional mind's eye" inspecting and interpreting his quasi-pictures. If this is nothing supernatural, however, but just more brain activity, more electro-chemistry, (as Kosslyn clearly holds) then it is not at all clear that it helps us to understand how we could be conscious of a quasi-picture (or, come to that, a mentalese description) in our brain. (Indeed, Kosslyn does not claim that it does.)
Some philosophers do hold that consciousness of mental states arises from their being themselves represented within the brain by "higher order thoughts," and a "mind's eye" account of image consciousness would presumably fit this mold. However, the higher order thought theory has not gained widespread acceptance for a number of reasons (Lycan, 2000). It probably captures not so much the distinction between conscious and non-conscious states as that between those experiences that flit through consciousness unremarked, and those that are remarked, and perhaps thereby become remembered and/or reportable. Furthermore, it relies on the availability of a suitable account of the intentionality of the states in question, which may not be forthcoming (§3.2).
It might be objected that, this is all just a special case of the notorious, unsolved "hard problem" of consciousness: We just do not know how to explain conscious experience scientifically, so why should it especially concern us that we cannot explain it in the context of imagery? But although we can perhaps legitimately pass over the "hard problem" in some areas of cognitive theory, we cannot, in good faith, ignore it here. It is of the very nature of imagery to be conscious (or, at the very least, potentially conscious), and, very arguably (Külpe notwithstanding), all conscious experiences are imagistic, either perceptual or quasi-perceptual. The apparent intractability of the "hard problem" just may owe something to entrenched misconceptions about the nature of imagery.
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