Personality Theory

Personal identity has an established place in the philosophical universe but personality is not so sedulously studied. People have personalities (some animals too) but not much is said about them by philosophers (by psychologists, yes, where personality theory is part of the curriculum). Why not? There are some good philosophical issues here, and the subject is certainly of considerable intrinsic interest (and not just to philosophers). There is first the question of the ontological status of personality traits: what are these exactly? A psychologist will tell you about the Big Five personality traits–openness, conscientiousness, extroversion, agreeableness, and neuroticism—and you will have some idea of what she is talking about; but it is not so easy to say what having these traits consists in. The philosopher might lazily announce that such traits are dispositions to behavior without inquiring too closely into what precisely such a disposition might be, both with respect to its intrinsic nature and the range of behavior held to characterize the disposition. Is there any more reason to be a behaviorist about personality than any other psychological fact? The problem, evidently, is that personality traits are clearly not reducible to experiences or beliefs or speech or episodes of behavior, and yet they are perfectly real things. There may well be associated qualia and conduct, but these are not what such a trait is. The trait itself seems curiously elusive, being neither observable from the outside nor introspectable from the inside. It is perhaps the basis of a set of dispositions, which may be very various, but it is not simply identical to such a set—any more than molecular structure is identical with its associated dispositions. So there is first of all a fundamental question of ontology, with the usual threats of reduction, elimination, and mystery. We don’t have any clear idea of what a personality trait is.

            Other questions quickly crowd in. Is there something it’s like to have a certain personality trait, say extroversion, or is personality phenomenologically blank? Is personality a causal factor in the production of behavior, in addition to belief and desire and other recognized factors? Is it part of the explanation of intentional action? Does it cause action? How does personality relate to the brain? Could it be identical to a brain state? If not, why not (it has neither semantic content nor qualitative character)? Are traits of personality analyzable in any way: do they have compositionality or hidden structure? Are they definable? How are they related to desires? Certain desires seem characteristic of a given trait, but is there any necessary relation? Do extroverts always and necessarily desire to hang out with other people? What causes such traits to exist in an individual—genes, social interactions, education, reading habits? And what causes them to change and possibly disappear? How plastic are they? Can there be a complete alteration of personality? Traits don’t come and go like sensations or beliefs, but they do seem to be in a constant state of flux; they are not just passive elements of one’s psychological anatomy. They grow with age and can become atrophied. Are they supervenient on other parts of the psyche, particularly desires; or are desires supervenient on them? How exactly do personality traits interact with desires? Do they sometimes fix beliefs? These are all good questions, but we don’t find philosophers addressing them. It’s as if personality doesn’t exist so far as the philosophy of mind is concerned.    [1]

            Personalities notoriously vary, but are there any personality universals? Are there personality traits that all humans share? Is there a species personality? This question is like the corresponding question about languages; indeed, there is quite an exact parallel. Despite many local variations there is a substantial core of common traits—a human type. The same is true for other species, as any pet owner knows. Humans are apt to be acquisitive, competitive, social, family-oriented, hospitable, nervous, and afraid of death (among other things)—though there is much scope for variations of expression and different triggering conditions. No doubt this phenotypic coincidence has a genetic basis: we humans are born with a specific type of personality different from the personality of big cats and tortoises (say). Do humans always have a personality? There may be pathological cases, such as brain damage, and we have all heard the phrase “he has no personality”, but any normal human has one—though it may not be scintillating or agreeable. A personality is your birthright, for good or ill; you have no choice in the matter. You have one as surely as you have a body or brain. You might be able to have it removed, but then you will end up like the proverbial vegetable. You exist; therefore you have a personality. Indeed, you exist as a personality: that is what you essentially are. What makes me me is my personality more than anything else: take that from me and you rob me of my essence. You can take my memories, all of them, and leave me intact as long as my personality survives. If I have many personalities, you might be able to take some of them and leave me still on the premises; but if I am rendered a personality vacuum, I am effectively extinguished.

            How limiting is personality? Is it like having a limit to memory? Does your personality prevent you from achieving certain things? Is it possible to transcend one’s personality? We are certainly not free of our personalities (single or multiple), but is it possible to bracket them, to break free of them? The question is not easy: don’t we need another personality in order to break free of this one, or can we step into a personality void and proceed from there? Is there such a thing as personality-independent action? Some have thought that God can confer such an ability (think of Saul on the road to Damascus), but doesn’t there need to be some personality germ in there that makes such a thing possible? How can I just lever a brand new personality into being? Don’t I need a personality to do that, and mustn’t this personality somehow carry the new one within it? I can’t make myself be a patient person, say, simply by willing it (though I might be able to moderate my impatient actions). Aren’t we really imprisoned by our personalities? Don’t our personality traits form the bars of our existential cage? Don’t they sharply limit our freedom? At best you can use one trait to do battle with another (Agreeableness versus Impatience), but you can’t set yourself against your entire personality. Personality is fate. What personality is exactly is not so clear, but it is clear that it has a powerful grip on us. We do well to develop a sound philosophy of it.

    [1] I will refrain from cliched comment about the personalities of philosophers: is this why the subject is so neglected?

Knowledge, Memory, and Time

We have knowledge of the past, the present, and the future—or we think we do anyway. That makes three types of knowledge, classified according to time. But when you think about it you see that there is really only one type of knowledge: knowledge of the past.  [1] Knowledge of the future is based on knowledge of the past; it has no other source. We know what has happened so far and we project this knowledge into the future, relying on inductive inference. Knowledge of the future is simply knowledge of the past extrapolated forward: if there were no knowledge of the past, there would be no knowledge of the future. Knowledge of the present, so-called, is also really knowledge of the past: for it takes a finite time for a stimulus to cause a percept, and it takes a further finite time to form a belief based on a percept. By the time you have formed a belief about what is presently the case it may no longer be the case. This time lag is notoriously writ large in the case of distant astronomical objects: by the time you have perceived and formed a belief about such objects they may be long gone. Our knowledge is always of the past, though we may project it forward by making present-tense judgments, hoping that things haven’t changed too much in the interim. What we know is always strictly about what has been (this is true even for introspective knowledge, since it too takes time to formulate). In the most basic cases our knowledge is a trace of the past—an effect of a prior cause. In fact, there is always a complex sequence of events mediating the outside stimulus and the knowledge it eventually produces—events that are both computational and physiological, occurring in the nervous system. These function like memories of earlier events in that they involve holding information for later processing: the retinal image is a kind of memory of the light pattern that reaches the eye, and subsequent neural patterns are like memories of the retinal image. There is information storage over time, though the time might be measured in milliseconds.

Given that memory is the retention of information over time, we could say that all knowledge, including present-tense knowledge, is based on memory. Indeed, the light pattern that reaches the eye from a distant (and possibly extinct) galaxy might profitably be viewed as itself a type of memory of the galaxy in question: for the light preserves information about that galaxy over time, possibly for many years. The universe remembers! If we were to go externalist about memory, we could include this kind of information retention in the mechanisms of memory: the light preserves information about a remote object and then the nervous system of the observer preserves information contained in the light. In any case we have information preservation over time, the mark of memory. We can simplify matters theoretically by stipulating that the process of belief formation elicited by past events is a memory process: information retention is always a type of remembering. Even when an object is right in front of you now there is a complex memory process as information is gleaned, processed, and stored—eventually leading you to form a belief about the object (“This is red”). Subjectively it all seems to happen in an instant, but in fact there is always a time lag between the object having the property and the observer coming to know it has that property. If we were being very careful (the skeptic looking over our shoulder), we would more cautiously assert only that the object was red, albeit a fraction of a second ago. The sensory modules inside us, which have a much more fine-grained experience of time, might confine themselves to judgments along the lines of “I seem to recall that such and such an event happened in the recent past”. By the time the light stimulus makes itself felt in the visual cortex at the back of the head, after a long trip through the optic nerve and the brain, the retinal image might be a distant memory as far as our visual processors are concerned. The essential point is that information retention is the method whereby knowledge of the present is acquired—that is, knowledge of the past. In short, all knowledge is memory knowledge. When the positivists spoke of “observation statements” as forming the epistemic bedrock of science (and not just the positivists), they misspoke: it is memories of observation that form the basis of scientific knowledge. Observation itself is essentially a memory process, but in addition the observation must be retained over time, in memory and by means of external record (e.g. writing). The real basis of scientific knowledge is memory: no memory, no science. Everything we know about the world must be contained in what we remember about it. Our knowledge of the future and the present is really nothing but our knowledge of the past plus some inferential moves (more or less dubious according to the skeptic).

            The question must then arise as to how good memory is as a source of knowledge of the world. Does memory tell us how the world really is? Memory is, of course, notoriously unreliable, subject to distortion, fleeting and fallible. It needs some kind of external check if its deliverances are to be credited—and the checks too need somehow to be remembered. But that is not the point I want to emphasize: I want to focus on a deep structural feature of memory—what memory constitutively is. This feature is somewhat elusive to characterize, though we all recognize what it is; it tends to be described metaphorically or impressionistically. Hume spoke of memory images as “faint copies” of sensory impressions, which are vivid in comparison—as if memories are faded and worn, indistinct and blurry—and this description carries intuitive appeal. We might say that memories are impoverished or etiolated or drained of substance or sketchy or fragmentary or thin or insubstantial. Marcel Proust is the poet of memory as a feeble route to the past: it simply cannot recreate the psychological effect of past experience itself (this is why we are in search of lost time).  [2] Only the madeleine can bring back the past, enabling us to relive it, and even that cannot really recall the past experience in all its glory. Time past is time irrecoverable. Let me put the point this way: memory cannot provide us with a mode of apprehending the world that captures its full reality. Memories of the past are glancing, stripped down, and partial–ghostly remnants of what they purport to record. They are mere traces, like footprints in the sand: they don’t afford us the kind of full brimming knowledge of the past for which we yearn. They are not like seeing or touching or tasting something: remembering a taste is not like tasting a taste. It is true that some people reportedly experience the past in this quasi-perceptual way, and normal people can sometimes have remarkably vivid memories, but generally memory is a feeble conduit for knowledge of the past. It is normally pretty thin gruel. And once we appreciate the role of memory in perceptual knowledge we start to wonder how much is omitted even there: maybe a lot of information is lost between stimulus and response—even Humean impressions might be drastically etiolated compared to reality itself. If memory images are faint compared to sensory impressions, sensory impressions might be faint compared to the objective world; indeed they presumably are, given that enormous amounts of information don’t even get beyond the initial sensory receptors (the retina is by no means locally omniscient). We can conceive of creatures that have super vivid sense impressions, compared to which ours are pale and weak. In any case human memory is just not very saturated or all encompassing. And if memory is limited in this way, our knowledge must be too, proceeding as it does from such a bleached out basis. Our conception of reality is formed from our memories of it when you get right down to it, but memories are just not very rich or full or penetrating. Just think of your general conception of the past: it is shadowy, reduced, distant, full of blanks, and skeletal–even when operating at its most efficient. You really can’t think of the past as it is in itself (this was Proust’s lifelong lament). The past is gone, epistemically speaking; it is fundamentally irrecoverable, even when memory is accurate. The past is a shadow world (Plato should have used the parable of the cave to illustrate the feebleness of memory). But our conception of the world derives from memory and inherits its limitations. You might suppose that perceptual experience offers a way to something more vivid—more real—but don’t forget that experiences themselves become objects of remembering. Memories of experiences are themselves weak and faint, nothing like having the experience (and even that suffers from time lags and limited information retention). Fundamentally, our whole picture of the world is conditioned by our powers of memory, but memory is ineluctably Proustian—it can only offer us so much lost time.

Our epistemic relation to time is all out of whack: we can’t grasp time while it is happening, so to speak. Time is not obliging to human knowledge—not the past, not the present, not the future. We are always late to the party (or much too early in the case of the future), and poorly dressed and equipped. Time and human knowledge are just not cut out for each other. The result is that we view reality through a misty portal, a narrow and smoky window. This means that we never really grasp reality as it is, de re as it were; at best we form ideas that map its structure, or we feel its effects on our consciousness. God doesn’t remember the past, as if at a distance from it; he perceives the past—feels it in his marrow (or the divine equivalent). Think of an animal’s memory-mediated conception of reality, say a mongoose’s: that must be thin gruel indeed. Fortunately the animal is equipped with a bunch of instincts and doesn’t need to rely on abstract knowledge; we on the other hand fancy ourselves endowed with intellectual apprehension, while actually laboring under the constitutive limitations of memory. Memory is frustratingly flimsy, a perpetual source of existential angst, a Proustian nightmare. It all comes down to memory for us, but memory is very far from all there is. Reality itself has no truck with memory limitations and won’t agree to be represented by memory. Reality has all the talent and its agent memory is but a weak and impoverished echo of it. The past is always much more than memory can ever know.  [3]                             

  [1] I will put aside questions of innate knowledge; our concern here is with acquired empirical knowledge. A prioriknowledge is not temporally bound and is not founded in memory, but empirical knowledge of the world needs memory-assisted sense perception to get off the ground.

  [2] There is a good discussion of this philosophical theme in Proust (who was influenced by Bergson) in Nabokov’s Lectures on Literature (1980). Nabokov writes: “To recreate the past something other than the operation of memory must happen: there must be a combination of a present sensation (especially taste, smell, touch, sound) with a recollection, a remembrance, of the sensuous past… In other words, a nosegay of the senses in the present and the vision of an event or sensation in the past, this is when sense and memory come together and lost time is found again.” (p.249) I would add that such recreation can never be complete. Memory alone cannot do the job, so we need to supplement it with the more vital and full-blooded force of perception; but this combination is still impotent to produce the impact of direct past experience. Thus we search in vain for lost time: the past comes to us only in hints and morsels, despite that magical madeleine. The only way truly to recover the past is to travel back to it—and then we are still stuck with the memory-like nature of perception.  

  [3] Here we might speak, not so much of cognitive closure, as of cognitive claustrophobia—the feeling of being squeezed into a space too confined, cognitively speaking. This is the prison of memory: the way knowledge is held in check by the very nature of the memory faculty. And it is not just a matter of what is remembered but of the wayremembering works—that faintness, that etiolation, that fatal thinness. The world for us is a remembered world, but remembering is subject to extremes of deletion and dilution. The veil of remembering (as opposed to the veil of perception) is an apt metaphor: the past hides coyly behind this veil, showing itself only sketchily and dimly. This must condition the way we think of reality.

Is Existence Possible?

I am going to consider an argument for the conclusion that existence is not possible. Not that we don’t know that anything exists, or that nothing in fact exists, but that existence is impossible: it could not be that anything exists. This is, to put it mildly, a startling conclusion—startling to the point of jaw dropping. Yet it follows from relatively simple assumptions and requires no fancy or revisionary analysis of what “exists” means. The argument is not apodictic, but it is certainly worrying; it isn’t easy to see where it goes wrong, if anywhere. It starts with a fairly innocuous observation, namely that when new things come to exist they do so in virtue of pre-existing things, generally by being made of these things. Thus a new house is made of pre-existing bricks, a new painting is composed of paint that existed before, and a new organism is made of bits of matter that were already around. Nothing is truly new; everything is derived from something else.  [1] Let us say that things generally have a derivative existence. We can usually explain the existence of a new entity by reference to old entities that pre-date it: it is typically a matter of re-combination. Sometimes this procedure doesn’t work because there is (apparently) too much novelty in the new entity: notoriously, sentient beings have an existence not easily explained by the existence of what preceded them (insentient matter); similarly for organic beings in relation to pre-organic material. But here we generally assume that we are missing something, and it is clear that some aspects of the new entity owe their existence to pre-existing entities (such as the constituents of the body). Existing things come from other existing things, often going back a long time. Nearly all of what we observe in the way of existence is derivative existence.

            But isn’t there also original existence—things that exist without reliance on other things? What about the parts of newly existing things—where do they come from? They may in turn come from other pre-existing things, ultimately going back to molecules and atoms; and these entities may owe their existence to even earlier realities, given what we hear about the state of the universe at the time of the big bang. Maybe atoms derive from superhot plasma as it cools. But at some point we reach things that don’t derive their existence from other things: what should we say about these? Now matters are apt to turn sticky; a certain intellectual panic sets in. Our usual paradigm of existence starts to break down, since these entities don’t have an existence that can be explained in terms of antecedent entities. An array of more or less unpalatable options presents itself. The first is that these entities come from nothing at all: they simply spring into existence de novo. Not even God plays a role, since he is an existent being (allegedly) for whom the same question arises: what explains God’s existence? But putting God aside, we have the idea that the basic things of reality pop into existence from pure nothingness. This seems utterly incomprehensible: as the old adage goes, nothing comes from nothing. And if such a miracle were possible, why isn’t it still happening—why don’t we see things popping into existence out of nothing on a regular basis? It might seem that a dose of modal metaphysics could get us out of this jam: what precedes existence and provides its foundation is possibility. We might even change the terms of the discussion and describe the antecedent possibilities as themselves existing, so that the question becomes how possibilities become actualities. This is certainly an intriguing metaphysical theory: pre-existing possibilities give rise to the existing actual universe that we observe—not something from nothing but something from a possible something. There was a possible world existing before the actual world and it is the basis for the existence of the actual world; we just need to pump up our conception of reality and then we can find the basis for actual existence, thus preserving our usual paradigm of derivative existence. There are (at least) two problems with this approach. The first is that the same question will arise for the antecedent realm of existence: where do these possibilities come from? If possible worlds really exist, where do they come from—do they pop into existence from nothing? But second, and more decisive, possibilities have no tendency to turn into actualities; so they cannot play the role of existence generators. We can’t say that actually existing things are made of possibilities that pre-date them—what would that even mean? The relation between existence and possibility is nothing like the relation between a thing and its parts. This would really be another version of the something-from-nothing approach: things come to exist of their own volition, so to speak, without any earlier preparation or precursor or preamble—they just burst onto the scene at some assigned or random time.

            The obvious next move is to declare eternality: the original existences are nothing like the derivative existences, which have a time of origin and a finite lifespan, but are eternal beings without beginning or end. Thus we might suppose that elementary particles are eternal beings for which the question of origin does not arise. This is no doubt a tempting move (a knight’s move), given the unfolding dialectic, but it is far from satisfactory. First, it is flagrantly ad hoc: we are forced to make a clean break from our usual conception of existence in order to solve a metaphysical puzzle. We have no other reason to postulate eternality for non-derivative existences than to solve the problem of how certain things manage to exist; and on the face of it the idea sounds preposterous. It isn’t that these entities are like numbers in being (arguably) necessary existences: they exist contingently but eternally. So it is not in their very nature as necessary beings to exist in all possible worlds at all times; no, they are contingent beings that just happen to exist for all time. Nor is it clear that this postulation would solve the basic problem: for isn’t there still the question of what explains the existence of these entities? Let’s assume they exist eternally: we still need to know why they exist at all, given that they don’t have to. Is their existence simply a brute fact with no explanation? But why these entities and not others—why the particular types of particles that populate our universe? Their existence remains a mystery even if they exist through all eternity. We can understand the existence of most of what we observe, since we see how the existence of one thing depends on the existence of another, but with the basic entities we are confronted with things that exist for no reason—unintelligibly, by brute stipulation. Surely it would be preferable if we could give some account of their existence as contingent beings: unlike numbers they exist in time and can change over time—yet we are told they have no origin, no means by which they came into existence. Is their allegedly eternal existence any more acceptable than saying that ordinary objects could exist eternally as a way of explaining their existence? Suppose we tried saying that sentient beings exist eternally, which is why we can’t explain their origin in terms of antecedent facts—wouldn’t that be totally unbelievable, a complete abnegation of intellectual responsibility?

            So we seem to have reached the conclusion that existence is impossible. It seemed as if we could understand the existence of ordinary objects by reference to pre-existing objects, but it turns out that we have no account of the existence of those objects—which means we don’t really understand the existence even of derivatively existing objects. In the case of non-derivative existence we have only an array of unpalatable metaphysical speculations, more or less desperate and ad hoc. We really have no understanding of existence at all when you get down to brass tacks. And it looks as if any type of existence will face this critique—what to say about the existence of the basic realities. In particular, are we really committed to the eternal existence of concrete contingent beings just by the very notion of existence? Was that part of the bargain when we agreed to operate with the concept of existence? Or are we forced to accept that existence can be conferred by nothing at all, or that it springs miraculously from mere possibility? None of this is remotely attractive; it all seems like a steep and whistling descent into metaphysical nonsense. Thus the proponent of the argument encourages us to draw the obvious conclusion: existence is impossible. Nothing exists in any possible world. The idea of existence is incoherent, puzzling to the point of paradox. It isn’t just that nothing does exist; nothing could exist. For existence leads us to the problem of how the basic existences come to be—for which we have no adequate account. Maybe there is an option we haven’t thought of, or maybe existence is an impenetrable mystery; but as things stand, it looks as if we have a kind of proof that existence is impossible. We are familiar with arguments that purport to show that meaning is impossible, there being no workable account of what meaning is  [2]; the present argument purports to show that existence itself is impossible—of meanings, of material objects, of selves, of anything (except perhaps numbers). Ultimately, we have no conception of how the existence of the most ordinary things is possible.

  [1] It is an interesting fact about our universe that it permits the upsurge of new things: many things exist now that did not exist in the past. You would think that given the means at the universe’s disposal nothing new could be generated, just re-combinations of old stuff. This is why one can sympathize with the adage “There is nothing new under the sun”.  In some possible universes presumably this is the case—no new entities ever come to exist. In a sense existence is quite close to non-existence—that is, new entities are ontologically close to the entities they come from and can easily revert to them. It is surprising that they exist at all as separate things in view of this closeness. Why not just make do with the old things?

  [2] I am thinking of Kripke’s discussion of meaning in Wittgenstein on Rules and Private Language (1982). This is Zeno-level super-charged military-grade skepticism: the complete impossibility of both meaning and existence.

Wavelength and Color

We are told that wavelength determines color. But what does “determine” mean here? It is not in doubt that the wavelength of incoming light causes the perception of a specific color, though we should note that it only does so in conjunction with non-trivial facts about the perceiver’s eyes and nervous system. This is compatible with allowing that other types of stimulus could causally determine color vision: for example, the wavelength of sound waves might conceivably cause colors to be seen, or indeed a knock on the head. The causal relation is quite contingent and extrinsic with respect to the nature of color. What we know is that wavelengths are causally correlated with the perception of particular colors, but this is a far cry from supposing that they constitute what colors are. Kicks to the shins are causally correlated with bruises of various hues, but no one would suppose that bruises are kicks.

            Is there any closer relation? It might be supposed that an identity theory is possible: that way we would have a nice materialist account of what color properties are. It is worth being very clear about what this would mean, which requires us to be explicit about what wavelength is. According to the wave theory of light, light has a wavelike structure analogous to the waves you can see in the ocean: waves have both frequency (how many cycles reach a certain point in space per unit of time) measured in Hertz units, and they have length (the distance between successive crests or troughs) measured in meters. Wavelengths are very short for light waves and hence are measured in nanometers. The visible spectrum (between 400 and 700 nanometers) is just one part of the much wider electromagnetic spectrum.  Thus the identity claim is that a given color can be identified with waves of light with a specific distance between incoming peaks—this being nothing other than the phenomenon you can observe on many a beach (though involving a light medium not a water medium).  So the contention is that colors have a wavelike structure, travel through space, and have specific distances between their wave crests: red, say, is shaped like a wave, traverses space, and has a certain wavelength (longer than other colors). These are attributes of light, so by Leibniz’s law they must be attributes of color, if colors are identical to light waves. That is the nature of the color red, its true character, its inner essence: to be red is to have a particular wavelength, i.e. a certain distance between successive crests.

            But is this the way red looks? If you stand on a beach and look out to sea, you will see waves rolling into shore, and these waves will look to have a specific wavelength, generally of several meters: the shape and height of the waves is apparent to you and the distance between them is also apparent. These waves look precisely like the waves they are. But do colors look like waves? Evidently not: when you look at a red apple you don’t have an impression of waves of light approaching your eyes—you don’t see anything wavelike at all. You don’t see crests and troughs, or wave heights and the distances that separate them. The phenomenology of seeing colors does not include any perceiving of wavelike structure—you don’t, say, see red as having a longer wavelength than blue. Why not if colors just are wavelengths of light? You might say these waves are too small to see, that’s why you don’t see them—but they are still what visible color actually is. But if red were made of much bigger waves would we see them when we looked at a red object? Would red look like the waves it is if the waves were big enough to see? Clearly not: it would presumably look something like colorless ocean waves.  And if we looked through a microscope and could see our actual light waves, would we still be seeing red? No, the redness would disappear, to be replaced by magnified waves of light. So colors don’t appear to be wavelengths, as we ordinarily perceive colors—yet we are seeing some sort of property. The property we see cannot then be the property of being a wave with a specific wavelength.  [1] Some philosophers will respond by saying that these color appearances are actually appearances of light waves with their corresponding wavelengths, with no further property interposed between them and the perceiver. But this is a bad theory of perception: we clearly do perceive color properties when we see colored objects–we see things as red, blue, green, etc. But the property that we see can’t be identified with a wavelength property, because it looks nothing like a wavelength property. At the very least we would need to be given an explanation for why colors don’t look the way they intrinsically are, according to the identity theory; but no such explanation is forthcoming. So the phenomenological unreality of the alleged wavelike nature of color is a count against the theory that colors are identical with such properties.  [2] And it isn’t as if the way colors look gives us a hint of their real wavelike nature: there is nothing wavelike about the way color looks to us. If anything, colors look non-wavelike. We could, of course, go eliminative about colors, claiming that colors don’t really exist as properties, though light waves do—then there would be nothing that is not covered by the physics of color. But if we insist instead that colors are real and also reducible to wavelengths, then we have to face the question of why they don’t seem that way. On the face of it, the identity theory of color is refuted by the appearances. To be sure, wavelengths trigger the perception of color properties—they are the external cause of color perception—but they are not what color properties are. These properties are ontologically separate, a distinct realm of existence.

            There isn’t even a supervenience relation here, since the same wavelengths could correlate with distinct colors in different possible worlds, depending on the eyes that respond to these wavelengths. The correlation in the actual world is just that—a contingent correlation. Waves in the ocean often correlate with gleaming peaks and a crashing sound, but it would be quite wrong to think that there is some necessary connection here; a trip to a nearby possible world would quickly disabuse you of that misconception (in that world ocean waves form only at night and merely murmur). We must not mistake correlation for identity. The relationship between wavelengths and colors is an external contingent relationship not a relationship of identity or constitution. The reason colors don’t look like waves of light, equipped with frequency and wavelength, is that this is not what they are. The same can be said of heard sounds and sound waves in the atmosphere: pitches don’t sound like waves with frequency and wavelength because they are not such waves. We can hear waves in the ocean and gauge their frequency and wavelength, but nothing analogous is true of heard sounds themselves—they are not phenomenologically wavelike. Sound waves cause sound perceptions, certainly, but the sounds heard are not identical to sound waves in the atmosphere: one doesn’t hear middle C as a particular spatial separation of wave crests. Sensible qualities like these are not reducible to wave patterns in a physical medium.

  [1] A further point: if colors are identical to wavelength formations, which are invisible to the human eye, how come we can distinguish colors from each other? How can we tell that red is not the same as blue if we can’t see the wavelength difference that constitutes the difference of color? The obvious answer is that the property we see when we see red is not the same as the property of having a certain wavelength but is a property that is entirely visible to the human eye.

  [2] We may note, too, that wavelength is a continuous quantitative property, being simply distance between two points, but colors vary qualitatively and are discontinuous: red is not simply “longer” than blue. So wavelength is unable to capture the way the visible spectrum is divided up. There ought to be just one color, varying along a single dimension, if colors were definable in terms of wavelength.