Perceptual RepresentationContent, Constancies and Phenomenal Consciousness

Chapter 4 starts from Lewis's Hypothesis of Phenomenal Information and keeps the difficult part: information excludes alternatives.

The hypothesis of phenomenal information is the idea that phenomenal consciousness is informative. (…) According to David Lewis, there is an important hypothesis in this direction, which he calls 'The genuine hypothesis of phenomenal information,' which 'treats information in terms of elimination of possibilities' (Lewis, 1990, p. 94). (…) Note that while Lewis defines this genuine hypothesis of phenomenal information as necessarily excluding materialism, one need not do so. (…) I conjecture that when a space of possible representations, the 'map,' is indexed by the subject as a whole, then perception constitutively involves phenomenal information.

This is the hinge section: if information excludes possibilities, phenomenal character demands a structured quality space, not a bare list of alternatives.

Each phenomenal character constitutively excludes a certain range of possibilities, and the possibilities that each phenomenal character excludes is structured according to difference and similarity relations. (…) Notice that a quality space is not just a set of discriminations, but a structured set of discriminations. (…) The structured set of information gives rise to many dimensions along which particular discriminations are related according to similarity and difference relations.

IIT enters because the thesis needs a principled answer to what makes many discriminations one intrinsic point of view.

According to Tononi's theory, there are two aspects that make the phenomenal experiences what they are. First, phenomenal experiences are rich in information. They are informative. Second, this information is integrated. (…) What is needed is ultimately 'an intrinsic point of view associated with the camera chip as a whole'. (…) There is no objective measure that uniquely settles which states should be grouped together; that is, there is no intrinsic measure of which alternative representations are relevant, and which are not.

The thesis becomes concrete here: a perceptual episode is a definite coordinate in a structured space, not a free-standing actual item.

The 'map' part in the above example is the structured space of possible representations. (…) When Churchland speaks of indexing he means the precise way in which several such constancies are combined in a definite perceptual representational content. (…) The relation between 'map' and 'indexing' inherently appeals to structural information because information is understood here as the exclusion of possibilities; the map is understood as a structured set of possibilities, and the indexing is understood as the determination of one among many possibilities. (…) What this shows is that there are some exotic colors (phenomenal characters!) that figure in our color space that we are not even aware of, or worse yet, might consider impossible - such as 'impossibly dark yellow' and 'hyperbolic orange' (P. M. Churchland, 2005, pp. 548, 552). (…) The nature of the indexing remains mysterious and incomplete on MIMP.

The Case from Absence poses the silent-neuron question in perceptual terms: an inactive-but-present constancy and a congenitally absent one involve the same actual activity, yet do not contribute to content in the same way.

Consider the difference between a born blind person and an individual with normal vision staring into a dark or empty room. One might say that the person born blind sees nothing. The person with normal vision might also happen to see nothing. However, they do not see nothing in the same way. (…) One might claim that the person with normal vision represents an absence of visual content because he or she has certain visual constancies that are currently inactive. However, these very same visual constancies are also inactive when the person with normal vision sleeps in dreamless sleep, and yet in that case we would not similarly say that he or she represents the absence of visual content. (…) Thus, one may wonder what is required for an inactive constancy to enter positively into the perceptual representational content as an absence. What is necessary for being aware of absences in this way?