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Memory Wittgenstein raised the question of how we could distinguish inversion from misremembering, raising the issue of “whether the things stored up mayWittgenstein and Qualia / 101 not constantly change their nature” (Wittgenstein, 1993, p. 204). And Dennett (1988; 1991) has emphasized the issue of the unreliability of memory in arguing against inversion scenarios. Figure 4 shows a schematized Stage 1 at the top (that is the topmost of the 4 schematic depictions). Seeing a ripe tomato causes the subject to experience red which causes him to say “Red!”, indicating a normally functioning experience as of red. I symbolize a normal experience of red with ‘R’ as in Figure 1. I am assuming, contrary to the intervening argument, and purely for mnemonic purposes, that the inverted subject can be seen as abnormal withan experience symbolized with ‘G’. (Less mnemonic symbols that don’t make this mistake would be ‘X’ and ‘Y’.) The second portion shows the subject at Stage 2 where seeing the red tomato causes an experience as of green, which causes the subject to say “Green!”, indicating the complementary function. The bottom half of the diagram indicates two different versions of the situation at Stages 3 and 4. According to the possibility that I have been emphasizing (“phenomenal realism”), at Stages 3 and 4, red things look green. The subject says “Red!” because there has been a terminological inversion that cancels out the color perception inversion. But memory skeptics such as Dennett wonder how we can rule out the case schematized in the last line in which the compensating inversion occurs earlier than I imagined and the subject misreports his experience, remembering falsely what red used to look like. Dennett’s claim is that the two possibilities represented in the two scenarios at the bottom half of Figure 3 cannot be distinguished. However, he gives no reason to doubt that they can be distinguished empirically, as indicated in Figure 5. Figure 5 presents an implementation of the difference indicated in the bottom two scenarios of Figure 4. In the top case in Figure 5, the possibility that I have been emphasizing is elaborated. The subject at Stage 3 sees a ripe tomato and contrasts the way it looks colorwise with the way ripe tomatoes used to look. The machinery of this comparison involves a comparator device which compares the neural implementation of the experience with the neural implementation of the memory of previous tomato experiences. Of course, this story is physicalistic, but no more so I think than the Tuesday New York Times (see footnote 13). A Wittgensteinian who wishes to deny this level of physicalism would have to adopt a revisionary theoretical perspective, something that a Wittgensteinian should not do. The skeptical idea is that the memory is itself inverted, as is the experience, so when the subject compares them, the subject says the current experience is not what he remembers. The report is the same but the internal reality is not. Dennett wonders how these two hypotheses could possibly be distinguished. Since they cannot be distinguished, he thinks there is no real difference. (He is explicit about advocating “first person verificationism”.) My response is that there is no reason to doubt that the normal methods of science could distinguish them. For example, perhaps it could be shown that the memory representation does not change in the relevant period. Dennett might object that one can tell whether102 / Ned Block Figure 4. The phenomenal realist contrasted with the memory skeptic. See text. the memory representation in the brain changes only if one can distinguish the memory representation from the physical basis of the quale itself, whereas his point is that these cannot be distinguished. But since memory and experience are to some extent distinct, they must to some extent be distinct at the level of the brain. The point of the detail illustrated in Figure 5 is that once one makes the hypothesis concrete, the claim that the normal methods of science cannot possibly resolve suchissues begins to look like mere skepticism. The point is further illustrated by a different form of the skeptical hypothesis illustrated at the bottom of Figure 6. In this form of the skeptical hypothesis, the memory representation is actually the same as the perceptual representation, but because of an inversion involved in the comparison process, the subject thinks otherwise. Again, why should anyone suppose that the normal methods of science could not find the difference between this case, the one at the bottom of Figure 5, and the phenomenal realist hypothesis at the top of both figures? Some functionalists hold that the identity of experience and relations among experiences are constitutively tied to memory of those experiences. For example, Sydney Shoemaker (Shoemaker, 1996a, p. 147) says “The functional role of a quale must surely include the ways in which the instantiation at one time combines with instantiations of the same or different qualia at later times to produce certain effects…This means that the total realization of a quale will have to include the memory mechanisms by which qualia have the appropriate “downstream effects”. Functionalists often argue that in crucial cases it is arbitrary whether one says that experiences are qualitatively the same or thatWittgenstein and Qualia / 103 Figure 5. The bottom two hypotheses from Figure 3 elaborated. there is a memory illusion. Shoemaker and Robert Stalnaker (Shoemaker, 1996a; Stalnaker, 1999, 2006) have had an interesting debate in part about this issue, but more generally about whether the kind of combination of functionalism and physicalism endorsed by Shoemaker precludes an inverted spectrum. I am not a functionalist (Block, 1978, 1980; Block & Fodor, 1972). In any case, I don’t see that functionalism can be assumed in an argument against the possibility of an inverted spectrum, which is notoriously usable in an argument against functionalism. Further, since my argument does not require members of the inverted pair to be behaviorally or functionally indistinguishable, it is not clear that the functionalist argument will work against my point. 12. The Frege-Schlick View One interesting response to inverted spectrum arguments for qualia involves the doctrine that Shoemaker (1982; 1984; 1996a; 2006) calls the “Frege-Schlick” view, and the best defense of that view to date is Robert Stalnaker’s (1999; 2006). Shoemaker’s version of the Frege-Schlick view is that relations of qualitative similarity and difference only apply intrasubjectively and not intersubjectively. On this view, there can be a genuine issue about whether my experience of red is qualitatively the same or different from my experience of green now or last week but not whether my experience of red is qualitatively the same or different from your experience of red. On that version of the Frege-Schlick view, qualitative relations do not supervene on any conglomeration of naturalistic properties,104 / Ned Block and not surprisingly, Shoemaker’s 1982, 1996 and 2006 discussions of the issue reject it.30 Stalnaker’s version of the Frege-Schlick view is in a way much less radical because what his version rejects “is only a notion of qualia that is both independent of representational content, and also comparable across persons.” (2006, p. 391) He is happy to acknowledge interpersonal qualitative comparisons so long as they can be cashed out in representational/functional terms. In a way though, Stalnaker’s version is more radical than Shoemaker’s since he rejects intra-personal comparisons of experience over time as well as inter-personal comparisons of experience—if the qualities of the experience cannot be cashed out representationally/functionally. I said that skepticism about interpersonal comparisons of experience is incompatible with a generally physicalistic world view. To see this, suppose there are two people who are physical (and functional) duplicates looking at the same object, say the moon, from the same visual angle. Suppose also that they are identical in history of stimulation. Despite identity in everything about them and their environment, current and historical, that could reasonably be supposed to be relevant, the form of skepticism under discussion insists that there is still no issue of fact as to whether their experiences of the moon are the same or totally different. Hilary Putnam argued in response to a presentation of this paper at the Putnam at 80 conference (see footnote 1) that a single sufficient condition— perfect physical identity—does not establish a matter of fact for any other case or give us any reason to think there is any kind of a physically determined metric of similarity. Right, but there is no reason to doubt that normal procedures could not discover the determinants of many comparisons between people. As I mentioned earlier, Putnam himself has slightly different color vision in his two eyes. Consider Oscar and Elmer mentioned earlier, one of whom has a copy of Putnam’s left eye, the other of whom has a copy of Putnam’s right eye. If Putnam sees things grayer through the left eye (as he does), we have every reason to think that Oscar will see things grayer than Elmer, especially if we can pinpoint whatever it is about the retina or pre-retinal structures in Putnam’s two eyes that very likely are responsible for the difference. Further, examination of your eyes and mine could provide evidence that other things equal, your color vision is grayer than mine. One can imagine many cases in which one would be reasonably confident about a comparison between people, independently of any representational or functional theory or any other philosophical theory of the nature of experience. In short, we have mundane reason to believe certain interpersonal comparisons of experience. Wholesale rejection of interpersonal comparisons is incompatible withscientifically informed common sense. Stalnaker’s view conjoined with this fact entails that some sort of representationism is true. The possibility of an inverted spectrum is incompatible with leading versions of representationism, so not surprisingly, Stalnaker argues against the inverted spectrum.Wittgenstein and Qualia / 105 Figure 6. The top figure is the same as in Figure 5. The bottom figure illustrates a different sort of memory skeptic. Stalnaker’s argument is based in large part on two analogies, of which I will discuss only one. It depends on a relational theory of space. Consider an analog of an inverted spectrum for space. We can make sense of the idea that this table is moved 3 feet in the direction defined by the arrow from here towards say the Andromeda Nebula. And that this chair is also moved in that direction. But if everything moved in that direction, would the result be a universe in which everything has moved 3 feet from where those things are now? Of course not. What it is for something to move 3 feet in that direction is for it to move 3 feet relative to everything else. If object A moves 3 feet to the left, then when object B moves 3 feet to the left the “everything else” is slightly different from what it was in the case of A’s move, so in the end the relations that define position are the same as when we started. The suggestion is that in the intrasubjective inverted spectrum scenario, there is similarly no fact of change except relative to other color experiences. If they all shift, then there is no change at all. If one does not believe that the qualitative character of experience is entirely determined by relations to other qualitative characters of other experiences, then the analogy will look wrong. The analogy is certainly at variance with some aspects of common sense. For example, I think common sense leaves it open whether a color blind person can have exactly the same experience of say a black and white drawing as non-color blind people have, despite the fact that the color-blind person’s “color space” is different. But the most important point is that this is not an issue to be settled a priori or by common sense. The nature of experience—and I would say the same of the nature of space—is to be settled by the best scientific picture.106 / Ned Block Shoemaker (2006) makes another point about the analogy. On the relational theory of space that Shoemaker attributes to Stalnaker, diachronic distance is dependent on synchronic distance. Something at t2 hasmovedfromwhereitwas at t1 if its synchronic distances from other things are systematically different in the appropriate ways at t2 from its synchronic distances from those things at t1. But there is no comparable dependence of diachronic qualitative relations on synchronic ones. Shoemaker’s example (p. 22) is that if two colored lights are flashed, one after the other, I can compare the experiences of them without comparing either of them with the kinesthetic experiences, smells, sounds and aches and pains that accompanied either one of them. Some functionalists might suppose that there is a dependence on synchronic relations even if I don’t have to be aware of it in order to judge the relation between the two lights, but if that is the objection to Shoemaker’s point, then once again the defense of Stalnaker’s analogy appeals to the conclusion. Stalnaker (2006) replies that the relational view of space that he defends is not the one that Shoemaker attributes to him. On Stalnaker’s version of the relational view of space, diachronic distance is not dependent on synchronic distance. Bothkinds of distances are a matter of relations in a coordinate system. Actual objects are used to fix the reference of the coordinate system but not to define it in any stronger sense. On Stalnaker’s version of the relational theory, distances are real, but locations are conventional. So, once everything has moved 3 feet in the same direction, all relative distances are the same as at the beginning, and there is no overall motion with respect to any location. Here is a different analogy. Students of Galileo founded the Accademia del Cimento in Florence in the 17th Century. Members of the Accademia pioneered the study of heat phenomena, making the first thermometers, an example of which is found in Figure 7. These thermometers were marked with gradations visible in the picture, but the gradations were not carefully spaced and there was no attempt made to relate the gradations at one end of the scale to those of the other end or of one thermometer with those of another. At the beginning of their investigations, the experimenters did not know whether an intra-thermometer difference of 5 degrees at one end was in any objective way equivalent to an intra-thermometer difference of 5 degrees at the other end or whether there was any inter-thermometer correspondence between 5 degrees as measured by one thermometer and 5 degrees as measured by another. A big advance was made when thermometers and their scales were calibrated to specific freezing and boiling points such as the freezing and boiling point of water. Now there was a meaning to inter-thermometer comparisons, but it was still unknown whether an analog of Stalnaker’s theory of space applied. Perhaps there were facts about the temperature difference between the boiling and freezing point of water, but no “locational” facts about either point. That is, perhaps the only facts of temperature were distances between certain temperature points such as freezing and boiling points for various substances. But as it happened, that turned out false when it was discovered that temperature is mean molecularWittgenstein and Qualia / 107 Figure 7. kinetic energy and hence that there is an absolute zero point at which kinetic energy is zero. That is a “locational” fact that would correspond in the spatial arena to the discovery of a kind of “absolute” space. Which is the better analogy for phenomenal experience, Stalnaker’s space analogy or the temperature analogy? I don’t see how anyone could think this is an a priori question. There are two accounts, a functionalist account that roughly fits Stalnaker’s view and a physicalist account that roughly fits my view (Block, forthcoming). I think that there is some preliminary evidence that favors the physicalist view—some of which I have mentioned here—but my main point is that there is no way to be sure now. Different philosophers come to different conclusions based on their philosophical perspectives and their own sense of their own experience. 13. Conclusion I started with a shifted spectrum argument for qualia and then moved to an inverted spectrum argument. I provided evidence for the claim that a shifted108 / Ned Block spectrum is actual. My argument withrespect to the inverted spectrum was more modest: there is reason to think it is possible and perhaps actual. A key feature of my argument was that the versions of the shifted and inverted spectrum needed for qualia do not require behavioral indistinguishability of the shifted and inverted pairs—a point that disarms many objections. The upshot is that Wittgenstein is right to say “This is a very serious situation.”