Abstract
Naïve realists have yet to successfully discharge the problem of supersaturated hue, afterimage-experiences as of hued surfaces that are beyond-maximally saturated. The experiences are a problem for the view because supersaturation, qua property of external objects, is an impossible color property. Accordingly, the experiences cannot be handled in terms of their indiscriminability from perceptions of such surfaces, in the manner of Martin (2004). Nor can they be handled in terms of seen surfaces looking supersaturated, in the manner of Kalderon (2011). This ramifies for every naïve realist view which grounds perceptual phenomenology in relation to perceptions, or to the qualities perceptions reveal.
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Notes
I use ‘perceptions’ here and throughout factively.
Cf. Martin (2006, p. 19).
There are two things to note about this characterization of Badness. First, the characterization gives the naïve realist room to classify (so-called) illusory experiences as she sees fit. If, for instance, she thinks that the colors experience portrays a spinning Bentham disc (more on which later) as exhibiting are mind-independent (and apprehended), then she can classify such experience as Good. If instead she thinks experience gets things wrong in respect of the disc’s color, she can count it Bad. Second, the characterization says nothing of whether Bad cases are non-perceptual. And, so, naïve realists like Raleigh (2014), Ali (2018), and Masrour (2020) can consistently classify hallucinations as Bad and perceptual (involving, i.e., some sort of perceptual relation to mind-independent objects).
See Beck, op. cit., pp. 609 − 10 for a survey of the naïve realists who do this.
On the precisest characterization germane to RD, indiscriminability is cashed out as follows: for x to be indiscriminable from the Fs is for it to be impossible for an idealized subject, reflecting solely on epistemic context, to know x to be numerically distinct from the Fs (cf. Sturgeon, 2008, pp. 126–127; see also Fish, 2009, pp. 87–88, who follows Sturgeon 2006). Because appeal to neither contexts nor idealized subjects helps the disjunctivist with experience as of supersaturated hue, we can safely omit them in what follows.
As will become relevant later in § 3, that the proponent of the foil takes on these epistemological burdens is revealed, first, in the context of considering how she might answer the question how it is subjects know they could be victims of Cartesian “perfectly matching hallucinations” (Martin, 2004, Sect. 3, especially p. 47).
In Martin’s own words, because reflection on the Good case yields that NR is true, and because it is not manifest in experience that E1,…En are definitive of experience,
“it seems plausible that what links the case of hallucination to the veridical perception is the seeming presence of Naïve phenomenal properties and not E1 … En. In that case, common sense has no reason to discriminate against a case of perfect hallucination which lacks E1 … En but yet which seems to possess the properties relevant to its being an experience as of a street scene in the first place, the seeming presence of Naïve phenomenal properties” (49–50).
Here is Martin:
“[B]y immodest lights the kind of experience one has when seeing such a street scene is of just the same kind as any non-perceptual event which is not a perception but still an experience as of a street scene, namely an event with the properties E1 … En. Since nothing can be discriminated from itself, the immodest approach will hold that the modest one should agree that these events are indiscriminable from a veridical perception of a street scene and hence are perceptual experiences as of a street scene.
In a similar vein, Sturgeon (2008) motivates RD by appeal to parsimony. Because everyone, he says, agrees that experiences are (in general) indiscriminable from corresponding Good cases (119, 122), the theory which grounds the Bad case in indiscriminability is at a dialectic advantage vis-à-vis its rivals (122). Crucial to this motivation too is the assumption of RD’s extensional adequacy. For if experiences were not in general indiscriminable from corresponding Good cases, then the dialectic advantage would be lost.
For this use of ‘positively’, see especially Martin (ibid.) p. 71.
Or rather these views are guaranteed to assign identical grounds to Bad and Good cases where the cases share proximal causes; and there are many such cases possible. I return to this qualification in the following footnote.
Two important caveats are in order regarding my presentation of RDBad, one regarding my inclusion of RD as an important part of the route to RDBad, the other regarding a simplification I make. First, as a reviewer pointed out, many proponents of RDBad do not get to RDBad via RD—by, in other words, first conceiving of experience in terms of RD before then going on to posit specific grounds for the Bad case. What is perhaps more common is the proponent of RDBad goes straight from NR to RDBad via (i) the principle that there are psychological commonalities where there are shared proximal causes, plus (ii) screening-off considerations like the ones just discussed (see, for instance, Fish,, 2009, Soteriou, 2016, and the discussion of Martin’s view in Byrne and Logue, 2008). But if the naïve realist does not get from NR to RDBad via RD, then the shared psychological kind she lands on, indiscriminability, is seemingly plucked from thin air and ends up looking as a result under-motivated. Where RDBad is motivated instead by way of RD, it avoids looking ad hoc in this way: the shared psychological commonality becomes the unsurprising property being a perceptual experience. Martin’s original discussion does not have this problem (see especially Martin’s comments of the final paragraph of p. 64, leading into p. 65, of his 2004).
Second, downplaying the above, the proponent of RDBad might complain that a counterexample to RD is not eo ipso a problem for her because though she endorses RDBad, she can do so without endorsing RD. (And as we will see later, the problem case to be adduced below does not causally match any possible perceptions.) A couple points are appropriate here. First, this does not change that the experience to be discussed below is still a problem for RD. Second, consider the resultant view: a disjunctivism on which only causally matching Bad cases are grounded as per RDBad, and on which non-causally matching Bad cases have distinct grounds from both causally matching Bad cases and from the Good case. I have already said such a view is ad hoc. But I focus on RD to the exclusion of its non-reflective cousins because of its superior parsimony. (I will say more on this in the main text shortly.) And the profligacy and complexity of the view just described cancels out whatever advantage it might have enjoyed in terms of modesty (Martin, 2004) or parsimony (Sturgeon, 2008). For the above reasons, I simplify the discussion as I do.
Here is Hurvich (1981) on the phenomenon:
“If the primary excitation in a small foveal field in an otherwise dark surround is produced by, say, 500 nm, it looks green while the stimulus is on. If we turn the stimulus off and look at a small not-too-bright achromatic surface, we see a red afterimage. If the afterimage is superimposed on a small red field, we perceive a SUPERSATURATED red” (187).
It is best to remain relatively shtum with respect to exactly which quantity this is. Color scientists are generally not concerned with what external properties saturation (or hue, or lightness) supervenes on, and so there are scant proposals regarding what that supervenience base is. (This might have to do with the trend among color scientists to identify colors with qualia, a trend it is beyond the scope of this paper to weigh in on.) And for that, it is difficult to prove something exhibits the highest possible degree of saturation. Presumably, proofs need to be indexed to specific supervenience proposals. Happily, there is at least one proposal on which the claim of metaphysical impossibility goes through. On Churchland’s (2007) account, saturation supervenes on the tilt-angles of the canonical approximation ellipses of reflectance curves. And experiences as of supersaturated hues can be induced over surfaces which exhibit maximal tilt-angle (if Churchland, 2005, is anything to go on—particularly pp. 188 − 90).
With that said, it may be that pinpointing a supervenience base is unnecessary. A popular idea in contemporary colorimetry is that it is impossible for a surface to be more saturated than one the reflectance curve of which is in so-called Schrödinger form, where this involves light at any given wavelength being either fully reflected or fully absorbed, with no more than two transitions in the reflectance curve (for helpful discussion, see Koenderink, 2010, ch. 7.2). The proofs for this claim seem to go through without the supervenience base of saturation being known. If reflectance curves in Schrödinger form are maximally saturated, then experience as of supersaturated hue can be achieved by fatiguing or potentiating relevant neurons before fixating on a surface the reflectance curve of which is in Schrödinger form.
After I explain in § 3 why experiences as of metaphysically impossible properties give us counterexamples to RD, I address in footnote 26 the extent to which the argument of the paper would be different were supersaturation to turn out to be just nomologically, but not metaphysically, impossible.
I find that doing this makes things easier to follow. And I take no stand on the metaphysics of possibilities: what I say is consistent with their being Lewisian spacetimes, maximal consistent sets of propositions, or less-than-maximal consistent sets of propositions.
The irrelevant circumstances of chief concern are those in which subjects engage in theoretical reflection capable of bringing to light the impossibility of the perceptions (like that of § 2). For useful discussion regarding which circumstances are relevant, see Sturgeon (2008, Sect. 6.1 and 6.4).
I leave open that there may be other reasons. I mention what may be a further such reason in the following footnote.
Heather Logue (in correspondence) says it is better to think of Martin as committed to phenomenal character being shared across Good and Bad cases but to phenomenal natures being distinct, basing this reading on Martin (2002b).
What follows is an interpretation of what Martin explicitly says. So far as I can tell, Martin does not explicitly say how it is that, upon embracing RD, subjects do know the Cartesian possibility.
Does the argument work differently in the case that supersaturated hues, and perceptions of them, are not metaphysically impossible but just nomologically impossible? I think so. The reflective disjunctivist could then say that experience as of supersaturated hue consists in indiscriminability from metaphysically possible perceptions of supersaturated hue. Such a grounding story, though, undermines RD’s claim to naturalism (Martin, 2004, § 1, especially pp. 39–40). This is the idea that experiences take part in the “natural causal order” (ibid. p. 39). Here is how it undermines it. Recall that perceptions are not explanatorily screened off by the indiscriminability property they share with hallucinations because the explanatory oomph of that shared property derives from that of perceptions. This means that the explanatory oomph of those hallucinations grounded in indiscriminability from nomologically impossible perceptions would derive from those nomologically impossible perceptions. This is a bad result if perceptions earn their explanatory keep thanks in large part to the causal roles they play. Because then we would be seeing indiscriminability properties earning their explanatory keep thanks to their connection to causal roles they could only play were the laws of nature different. That is, the properties’ causal-explanatory power hangs on laws we do not have. This is dubious naturalism. (Interestingly, we can probably say this same thing with respect to grounding the experience in indiscriminability from metaphysically impossible perceptions.)
The argument also works differently, n.b., where the property experienced is logically impossible. As Siegel shows (2004, 2008), in such cases, reflection on context rules out that there are any corresponding perceptions and, so, the experiences are known to be distinct from any such perceptions (given the perceptions’ known nonexistence). This is a problem for RD because RD then assigns the experience no character. Siegel thinks this happens with hallucinated Escher scenes. Below we will see how Martin handles Escher cases.
Or “entirely veridical” as Martin might put it (cf. 2006, p. 357).
However, see Siegel (2004, fn. 6) for the complaint that it is ad hoc and tailored to one example.
In color science textbooks (for instance, Kuehni, 2003), it is one of the fundamental dimensions along which color experiences differ—the others being hue and lightness.
I am grateful to an anonymous reviewer for getting me to consider this reply.
Martin is openly sympathetic to the possibility of bringing about phenomenal experience by direct stimulation of the brain (2004, passim). (Compare also his discussion of Austin’s Sense and Sensibilia wherein he takes direct-stimulation possibilities to provide good support for arguments from hallucination; Martin, 2007.) However, because there are thorny issues here regarding whether the possibility, by disjunctivist lights, is undermined due to the lack of existing perceptions which proximally causally match, I will not rest my response on this first possibility.
Note that we should not say that what indiscriminability fixes here is the experience’s being as of something more saturated than it in fact is. Reflection on context rules out that anything is ever more saturated than it in fact is. (Now the case bears affinities to Siegel’s; see footnote 26.)
In one particularly interesting case (753 − 55), a circle that, when stationary, is black and white all over looks to subjects, when it is spun, variously hued. Kalderon says this multicolored-look too is a feature of the spinning circle and is no illusion. The spinning circle itself possesses the look-feature to which subjects come to be visually related (766, 773 − 74).
To avoid complicating things, I will stick here with Kalderon’s example of experience as of supersaturated red.
This sort of response was suggested to me by Craig French in conversation.
As an anonymous reviewer rightly pointed out, if supersaturation turns out just to be nomologically rather than metaphysically impossible, then the truth-makers of looks-statements about supersaturated hue become, less objectionably, the goings on of metaphysically possible worlds. But my hunch is that relying on this fact forsakes an otherwise attractive Parsimony understanding of what looks are, this being the idea that looks are identical to the ordinary visible properties of objects that we already accept as existing, like colors and shapes (Martin, 2010, pp. 161, 162; see also French and Phillips, 2020, p. 12). In keeping with Parsimony, the feature of the orange surface, the one over which the afterimage is as it were superimposed, which is relevantly similar to the paradigm look of a supersaturated orange thing is identical to its orangeness (cf. French and Phillips, op. cit., p. 12). With what, then, is the paradigm look of a supersaturated orange item identical? Taking a cue here from ordinary cases, it must be identical to the item’s supersaturated orangeness. (In the way, were we to say a green thing in such and such circumstances looked relevantly similar to a paradigm blue thing, we would identify the paradigm look of a blue thing with its blueness.) But supersaturated orangeness is not an ordinary property of objects that we already accept as existing. So, in aspiring to Parsimony, the naïve realist must also give it up. Aside from that worry, in positing the goings on of nomologically impossible worlds as truth-makers, the naïve realist in the unhappy position of ascribing experience unnatural grounds, which again feels at odds with naturalism (in a way not unlike the suggestion of footnote 26). To be sure, these remarks are not knockdown. But much of the argument in this section is intended just to undermine the appeal of, rather than to refute, a certain strategy.
It is worth noting that Kalderon’s failing to convincingly accommodate supersaturated hue does not ramify for his recommended handling of illusions more generally. After all, if Kalderon accepts Bad cases exist, then he already needs to say something different about their grounds. He could accordingly categorize afterimage-experiences as of supersaturated hue as Bad cases. (And there is already precedent in the naïve realist literature for categorizing afterimage-experiences this way: Brewer, 2011, p. 115). And if afterimage-experiences as of supersaturated hues (or afterimages in general) are appropriately categorized as Bad cases, then there will be less temptation to think of them as visual illusions.
Note that this is true of any counterexample to RD, and there may be more. See, e.g., Smith (2008) for a battery of further putative counterexamples. And then there are the many color-experiences mentioned in the introduction. I focus, however, just on experience as of supersaturated hue because it is a challenge for NR that proponents of the view themselves have acknowledged and because discussion of how the other color-experiences cause trouble for NR would have oversaturated the present discussion.
There is more to say for Beck’s account, however. In his (2019b), Beck argues there are two crucially distinct notions of phenomenology, one narrow one broad, just one of which (the broad one) is at work in discussion of the main motivations for NR. This multiplication of notions could allow for the sort of differential support that goes into motivating neurocomputational naïve realism.
I am not arguing no novel such solution can be given. See Logue (2013) for a proposed circumvention of the problem. Note, though, that, as intimated in footnote 16 above, if the naïve realist does not get to RDBad via RD, then her commitment to RDBad feels undermotivated. And with RD off the table as a conception of experience-in-general, and, so, unavailable as a route to RDBad, she cannot rely on it now. The tripartite run-of-the-mill disjunctivism, then, is bound to have an undermotivated feel about it.
We might also think this move implausible for being too pessimistic about the possibility of making computer-generated images from which afterimage-experiences are indiscriminable. If experiences of such computer-generated images are perceptions, then afterimage-experiences are indiscriminable from them and, so, responsibility for them is not so easy to shake. (Cf. Lycan, 2019, who argues for the possibility of making computer-generated images that phosphene-experiences resemble.)
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Acknowledgements
I am grateful especially to Scott Sturgeon, Maja Spener, and Heather Logue for discussions about the main argument of the paper and extensive comments on previous drafts. I want also to thank Harry Goldborn, Jess Sutherland, Aisha Qadoos, Tom Davies, Nick Emmerson, and Sam Andrews for comments and suggestions. And I want lastly to thank the two anonymous reviewers at Synthese thanks to whose feedback the paper benefited enormously.
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This research was supported by the ISRAEL SCIENCE FOUNDATION (grant No. 916/21).
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Sharp, W.A. Naïve realism and supersaturated hue. Synthese 200, 505 (2022). https://doi.org/10.1007/s11229-022-03994-3
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DOI: https://doi.org/10.1007/s11229-022-03994-3