Online research in philosophy

Martine Nida-Rümelin (1996) argues that color science indicates behaviorally undetectable spectrum inversion is possible and raises this possibility as an objection to functionalist accounts of visual states of color. I show that her argument does not rest solely on color science, but also on a philosophically controversial assumption, namely, that visual states of color supervene on physiological states. However, this assumption, on the part of philosophers or vision scientists, has the effect of simply ruling out certain versions of functionalism. While Nida-Rümelin is quite right to search for empirical tests for claims about the nature of visual states, philosophical issues remain pivotal in determining the correctness of these claims.

There has been much written in recent years about whether a pair of subjects could have visual experiences that represented the colors of objects in their environment in precisely the same way, despite differing significantly in what it was like to undergo them, differing that is, in their qualitative character. The possibility of spectrum inversion has been so much debated1 in large part because of the threat that it would pose to the more general doctrine of Intentionalism, according to which the representational content of an experience fixes what it.

Intentionalism holds that two experiences differ in their representational content if and only if they differ in phenomenal character. It is generally held that Intentionalism cannot allow for the possibility of spectrum inversion without systematic error, unless it abandons the idea that, for example, the qualitative character of color experience is inherited from the qualitative character of colors. The paper argues that the conjunction of all three -- the possibility of spectrum inversion, Intentionalism, and the inheritance thesis -- can be consistently, and plausibly, accepted.

(Wittgenstein, 1968) endorsed one kind of inverted spectrum hypothesis and rejected another. This paper argues that the kind of inverted spectrum hypothesis that Wittgenstein endorsed (the "innocuous" inverted spectrum hypothesis) is the thin end of the wedge that precludes a Wittgensteinian critique of the kind of inverted spectrum hypothesis he rejected (the "dangerous" kind). The danger of the dangerous kind is that it provides an argument for qualia, where qualia are (for the purposes of this paper) contents of experiential states which cannot be fully captured in natural language. I will pinpoint the difference between the innocuous and dangerous scenarios that matters for the argument for qualia, give arguments in favor of the coherence and possibility of the dangerous scenario, and try to show that some standard arguments against inverted spectra are ineffective against the version of the dangerous scenario I will be advocating. The leading idea of the paper is that an argument for qualia based on spectrum inversion does not require that the inversion be behaviorally indistinguishable. At one crucial point, I will rely on a less controversial version of an argument I gave in Block (1999). Wittgenstein's views provide a convenient starting point for a paper that is much more about qualia than about Wittgenstein.

The possibility that what looks red to me may look green to you has traditionally been known as "spectrum inversion." This possibility is thought to create difficulties for any attempt to define mental states in terms of behavioral dispositions or functional roles. If spectrum inversion is possible, then it seems that two perceptual states may have identical functional antecedents and effects yet differ in their qualitative content. In that case the qualitative character of the states could not be functionally defined.

I argue that the inverted spectrum hypothesis is nota possibility we should take seriously. The principlereason is that if someone's qualia were inverted inthe specified manner there is reason to believe thephenomenal difference would manifest itself inbehaviour. This is so for two reasons. First, Isuggest that qualia, including phenomenal colours, arepartly constituted by an affective component whichwould be inverted along with the connected qualia. Theresulting affective inversions will, given theintimate connections that exist between emotions andbehaviour, likely manifest themselves in behaviour, inwhich case the underlying phenomenal differences canbe functionally captured. Second, I argue that othersense modalities lack the structural featuresnecessary for undetectable inversion which, because oftheir analogy with colour qualia, weakens theplausibility of such an inversion in the original caseof vision.

Functionalism, a philosophical theory, has empirical consequences. Functionalism predicts that where systematic transformations of sensory input occur and are followed by behavioral accommodation in which normal function of the organism is restored such that the causes and effects of the subject's psychological states return to those of the period prior to the transformation, there will be a return of qualia or subjective experiences to those present prior to the transform. A transformation of this type that has long been of philosophical interest is the possibility of an inverted spectrum. Hilary Putnam argues that the physical possibility of acquired spectrum inversion refutes functionalism. I argue, however, that in the absence of empirical results no a priori arguments against functionalism, such as Putnam's, can be cogent. I sketch an experimental situation which would produce acquired spectrum inversion. The mere existence of qualia inversion would constitute no refutation of functionalism; only its persistence after behavioral accommodation to the inversion would properly count against functionalism. The cumulative empirical evidence from experiments on image inversion suggests that the results of actual spectrum inversion would confirm rather than refute functionalism.

Philosophers who advocate the possibility of spectrum inversion often conclude that the qualitative content of experiential states pose a serious problem for functionalism. I argue that in order for the inversion hypothesis to support this conclusion one needs to show that it generalizes to all species of qualia. By examining features of touch, taste, and olfactory sensations, I show there is good reason to resist this generalization, in which case appeals to the possibility of spectral inversion are considerably less effective than they may initially appear.

Even if spectrum inversion of various sorts is possible, spectrum inversion without a difference in representation is not. So spectrum inversion does not pose a challenge for the intentionalist thesis that, necessarily, within a given sense modality, if two experiences are alike with respect to content, they are also alike with respect to their phenomenal character. On the contrary, reflection on variants of standard cases of spectrum inversion provides a strong argument for intentionalism. Depending on one’s views about the possibility of spectrum inversion, the impossibility of spectrum inversion without a difference in representation can also be used as an argument against a variety of reductive theories of mental representation.