Colour and qualia

6. Replies

There have been three basic responses to these anti-functionalist arguments. The first is to grant their cogency and claim that for experiences such as subjective red, as opposed to cognitive states such as belief, functionalism is wrong and the traditional identity theory is right. But then one must confront the objections to that theory discussed above: the multiple-realizability argument and the explanatory gap.

The second sort of response is to attempt to undermine the intuitive resistance to a relational account represented by the absent and inverted qualia hypotheses. Numerous such attempts have been made, but we will focus on two related strategies in particular: what might be called the ‘asymmetries’ strategy and the ‘subtle role’ strategy. In the end they are both problematic, but they represent serious attempts to meet the challenge and their problems are instructive.

The basic idea behind the asymmetries strategy is to argue that an appropriately chosen and sufficiently rich relational description can uniquely identify a type of qualitative character, and thereby get around the sorts of counterexamples just discussed. Consider the inverted spectrum argument. As presented above, it seems to make the assumption that there exists a natural axis of symmetry dividing the colour cone. However, there is empirical evidence to the effect that this is not so (see Colour, theories of).

First, there is the question of the location of the primaries. It seems evident that some hues are experienced as combinations of others, while some seem not to be. Contrast a pure red or green with orange or purple. One might have thought that pure examples of each of these primaries would occupy points in the three-dimensional colour solid equidistant from the origin, representing equal amounts of brightness and saturation, and equidistant from complex hues. But not so. Yellow, for instance, occupies a point of higher perceived brightness than do the other primaries. Also, some primaries occupy a larger region than do others; that is, there are more steps to be taken before we describe what we see as a combined hue. Furthermore, there is the anomaly of brown, which results from darkening yellow, yet is not thought of as merely dark yellow but another hue altogether. The point is that if you were to invert along the red–green and blue–yellow axis, it does not look as if all the relational judgments would be the same. Normals would consider dark and light blues to have the same hue, but inverts would not. Normals and inverts would differ in when they considered hues to be combinations, as opposed to primaries. Functional identity between normals and inverts could not be maintained. Hence, they would not be functionally identical to us, and spectrum inversion would not constitute a counterexample to functionalism. (See Harrison 1973; Clark 1993; Hardin 1988 for arguments along these lines.)

The second, ‘subtle role’ strategy is aimed more at the absent qualia hypothesis. The idea here is to attack the notion that a creature could be functionally identical to us and yet lack qualia by demonstrating that qualitative character is itself essential to normal functioning. Van Gulick (1993) notes that there is some evidence, for example, from blindsight cases – in which a patient claims not to see anything within a certain region of their visual field and yet can correctly ‘guess’, upon prompting, whether or not something is there – that consciousness is necessary for carrying out certain functions (see Consciousness §7; Unconscious mental states). For instance, blindsight patients tend not to initiate action with respect to the objects that they can passively detect in their blind field. If, as such cases suggest, consciousness is essential to the performance of certain functional roles, then it is not possible for a non-conscious state to play the same functional role. Hence, absent qualia are not possible.

We said above that there are problems with both strategies. With respect to the asymmetries strategy, there are two basic objections. First, even if the geometric space that characterizes our colour experience is in fact asymmetrical in the way described above, this seems to be a contingent feature of it. Why should this matter? So long as it is not demonstrated that it is essential to qualitative experience that it be immune to inversion, we have no reason to believe that all forms of qualia will have this feature. But if any form of qualitative experience is susceptible to inversion, functionalism is in trouble.

Moreover, as suggested earlier by the case of red–green colour blindness, there could easily be cases of individuals whose colour experience is somewhat, but not completely, different from our own. Suppose that theirs is symmetrical, and therefore subject to inversion. Would it not make sense to say that when such a person looked at a red fire engine they were having an experience that was more like our subjective red than, say, our subjective green? But, if inversion were possible for them, we could not say this solely on the basis of their functional organization.

The second problem with the asymmetrical approach is that it does nothing to address the absent qualia hypothesis. Suppose that any inversion of primaries would be detectable. Still, given cases like Block’s China-head, it seems possible that a creature could realize a structure onto which the complete set of similarity relations definitive of the colour solid could be mapped, and yet there be nothing it is like to be that creature. Addressing the inverted qualia argument alone does not save functionalism.

The ‘subtle role’ strategy is, of course, specifically addressed to absent qualia. But here too there is a problem. Suppose we have to grant that there may be jobs, or roles, that only qualitative states can fill. That still does not mean that filling that role is what it is to be a qualitative experience. In fact, that very way of putting it – that being qualitative is essential, or necessary to playing the role – seems to imply just the reverse; that being qualitative is one thing, playing the role quite another. Suppose it turned out that being red was essential to some plant’s playing the ecological role it played; nothing that was not red could do it. We would not say that being red is to play that role, but rather that being red is what makes the plant in question especially suited to play that role. It seems that the same goes for subjective red – the qualitative experience of seeing red – in the scenario Van Gulick envisaged.

Nor is it clear how the ‘subtle role’ strategy addresses Block’s counterexample concerning the nation of China. Either one would have to admit that the entire nation experienced subjective red, or one would have to argue that the lack of qualitative character in this case posed an insuperable obstacle to realizing the relevant functional description. Both positions are difficult to defend. However, some (see Lycan 1987) have argued that there are other constraints – for instance, extremely fine-grained functional descriptions couched in teleological terms – that would rule out the nation of China as a legitimate realization (see Functional explanation).

In discussing the problems for functional accounts of colour qualia, we have not distinguished among various forms of functionalism. In particular, we have not addressed the representational version of functionalism, according to which colour qualia are functionally specific forms of representations of colour properties. It is sufficient to note here that the absent and inverted qualia hypotheses cause problems for this version of functionalism as much as any other. For suppose that an inverted spectrum is possible. Then two states could differ in their qualitative character and yet carry the same information concerning the reflectance properties of distal stimuli. Or, if absent qualia are possible, then a state could carry information concerning the reflectance properties of a distal stimulus and yet there be nothing at all it is like to occupy the state. If either case is possible, one cannot identify qualitative character with the representation of such properties (see Semantics, informational).