I happened to be watching a repeat of SNL last night and was struck again by a sketch about cancel culture. A preening pair, woman and man, were congratulating themselves on their activities in canceling young children. The kids were aged from 3 to 5 and the pair were relishing their destruction of the future lives of these miscreant infants for saying things deemed “problematic”. It really wasn’t funny except in the darkest way. It nailed the psychology of this recent exercise in violence perfectly.
Knowledge of Color
As colors have a metaphysics, so they have an epistemology. In addition to ordinary empirical truths about what colors objects have, there are also general truths stating a priori necessities: for example, “Orange is closer to red than to blue”, “There cannot be reddish green”, “Nothing can be white and transparent”, and “Nothing can be red and green all over”.  There is also knowledge of what colors in themselves are (“knowledge of things”): we know what red is, for example. We know quite a lot about colors before we even get to questions about the empirical distribution of colors among objects. Compare shapes: we also know a lot about shapes, both what they are and general truths about them, in addition to propositions about the shape of particular objects. This knowledge is also of a priori necessities. But there is a difference between shape and color: there is no analogue of geometry for color. There is no mathematical science of color comparable to the mathematical science of shape. There are no color theorems analogous to the theorems of Euclid’s Elements. There is barely a mathematics of color at all, though colors do form an abstract structure. Nor can we conceive of colors as derived from anything analogous to lines, as geometrical figures are so derived: you can form circles and rectangles with simple lines, but you can’t form red and green from a single basic chromatic primitive. Colors just don’t have the requisite degree of structure or quantitative character to allow a color geometry. Sounds are closer to shapes in this respect, as evidenced by musical theory: scales and keys are derived from mathematical relations of pitch (pitch being like line, constructively). But colors aren’t structured like closed many-sided figures, and there is nothing like angle in color space. So our knowledge of color doesn’t include anything comparable to geometrical knowledge, despite being a priori and necessary. Colors are not mathematizable in the way shapes are.
One might speculate that this is because colors are less objective than shapes. If colors are really experiential properties in disguise, then maybe it is the non-mathematical nature of experience that underlies the absence of a geometry of color. The same would not be true of shape, since we can separate objective shape from subjective shape: geometry is about objective shape not experienced shape; and maybe experience of shape is not susceptible to mathematical treatment either. But that kind of subjectivism doesn’t seem correct in the case of knowledge of color: such knowledge is not knowledge of experience as such—we are not thinking about experiences of color when we recognize general truths about color. Perhaps there are deep a priori connections between facts about color and facts about experiences of color, but it seems wrong to suppose that truths concerning color are simply analyzable as truths about experience—a color isn’t an experience! We have experiences of color, but the color of an object is not an experience in the perceiving subject. So the character of our knowledge of color is not immediately explicable in terms of our knowledge of color experience. Further, if we ask why experience of color is not mathematizable, the answer must surely advert to what such experiences are of, viz. colors: but this returns us to the non-mathematical character of colors themselves. There is much more hope of a mathematics of shape experience, given that such experiences are of shapes, which have a developed geometry to call their own. It appears, then, that it is colors as such that resist mathematical treatment: being red is not like being an equilateral triangle—the property itself lacks internal mathematical structure. This is just a basic ontological fact.
Here is another difference between color and shape: there is nothing analogous to space in the color case. What I mean by this has to be carefully stated: shape can be viewed as a mode of space, but color can’t be viewed as a mode anything analogous to space. Space, like matter, has extension (at least in commonsense physics), and shapes are modes of extension; but there is nothing analogous that has some chromatic property of which the several colors can be viewed as modes. A red object (isolated from other colored objects) is not surrounded by a sea of color, in the way a square object is surrounded by a sea of space. Shaped objects exist in a medium that shares their geometrical nature, but colored objects don’t exist in a chromatic medium: space isn’t colored! The color is simply in the object not borrowed from the medium in which it exists. Space and shape are natural partners, but space is not a progenitor (or twin) of color—and neither is there anything else that plays the role of space in relation to color. There is not some milky stuff, say, that houses the colors we observe in objects. Given space, shape is not a surprise; but space doesn’t prepare us for color, which appears as a radical addition. Color just seems plonked down in space with nothing comparable to support it. There is no chromatic ether.
Knowledge of color might be cited as a basic type of knowledge that could illuminate other types of knowledge. Puzzles raised by other types of knowledge might have precursors in our knowledge of color, in particular knowledge of what is necessary and a priori. Wittgenstein compares mathematical knowledge to color knowledge, hoping thereby to demystify it.  The comparison might help resist platonic conceptions of mathematical knowledge, given that colors are relatively “concrete”. Certainly we can use color knowledge to argue for the non-uniqueness of mathematical knowledge in its synthetic a priori character: mathematical knowledge doesn’t stand apart from all other types of knowledge in having that kind of status. Even perceived colors can give rise to synthetic a priori truths—not just abstract platonic universals. But the other area that might be compared to color knowledge is knowledge in ethics, which is often compared to mathematical knowledge. It is felt that ethical knowledge needs all the help it can get in securing its epistemic credentials, and mathematical knowledge is then wheeled in as a precursor or partner in crime. The idea certainly has strong appeal for a moral realist convinced that moral knowledge is a species of a priori knowledge. But the color case might be an even better model for ethics, because it is less rigorous than mathematical knowledge and, well, less mathematical. The critic will point to the asymmetry in respect of proofs and general formal sophistication, thus pooh-poohing the comparison to mathematics; but the color case mirrors ethics more closely in these respects. Ethical knowledge resembles our knowledge of color in being synthetic and a priori, and neither is at the level of mathematical science. This is not to downgrade them: it is merely the way they are given the properties and facts concerned. Colors are just not intrinsically susceptible to mathematical treatment (save very superficially), and there is no reason they should be; analogously, moral values are not susceptible to mathematical treatment, and there is no reason they should be. So color and morality belong together epistemologically (we could also bring in sounds and even tastes and smells). In both cases we have a faculty of knowledge that delivers insight into the subject matter in question, thus delivering types of knowledge traditionally described as synthetic a priori (i.e. not analytic and not derived for experience). Anyone seeking to question the status of moral propositions in these respects must explain why they decline to take the same line for propositions about color. It turns out that synthetic a priori knowledge is quite common (and indeed commonplace) and not confined to the supposedly elevated areas of mathematics and morality. Even the humble colors, perceived by human and beast alike, can give rise to such knowledge. Being right is not so far from being red, epistemologically speaking. 
Colors and Powers Again
Locke distinguishes primary qualities from powers to produce sense impressions of them in perceivers, but he thinks that secondary qualities are “nothing else, but several powers in them, depending on these primary qualities…to produce several different ideas in us”.  That is, he identifies colors with powers to produce states of mind: that is what a color is—a causal power of a certain sort. I am going to make two rather brutal criticisms of this doctrine. The first is that causal powers are invisible but colors are not. Suppose I see an object as square: that quality is visible to me, but the power to produce an impression of square is not so visible. I don’t see an object ashaving such a power—I simply see it as having the geometric property of being square. As Hume taught us, we have no sense impressions of causal powers—though objects have them. Powers are actually rather mysterious things involving potentiality, and they concern relations between objects and other objects (in this case objects and perceiving minds). They aren’t intrinsic manifest qualities; they are rather like modal properties such as being possibly square. They aren’t things the senses can resonate to. So Locke’s theory implies that colors are invisible! Nowhere does he acknowledge that consequence, and it is indeed startling: surely we want a theory of color to be consistent with the visibility of color. I suppose he could just accept the consequence, but it is a hard bullet to bite. Maybe colors have the power to produce impressions of themselves, as shapes do, but they are not identical to such powers. In fact, the power to produce sense impressions depends on certain forces that exist in objects, but forces are not perceptible: we don’t perceive electrical or gravitational forces, only their effects. Yet we see colors quite plainly: they are nothing like hidden powers or potentialities.
Second, external physical objects are not the only things with such powers. Minds and brains have them too. Your mind has the power to produce ideas of secondary qualities in you, as it does when you hallucinate. In fact, it must have such powers if external objects are to elicit sense experiences in you; the external object alone cannot do this. The brain too must have the power to generate sense impressions, which it demonstrates all the time. But if colors are identical with such powers, then minds and brains are colored. They have these powers in virtue of possessing appropriate primary qualities, just like external objects, so they have the property Locke identifies with color: but they don’t have the very color that this power would entail. The mind isn’t red when it exercises the power to produce impressions of red, and neither is the brain. It is easy to see what is going wrong here: having the power to produce sense impressions is just too broad a condition to capture what color is. Couldn’t a super-scientist have such a power without having the colors that allegedly go with it? Nor will it help to limit the power to the surfaces of external objects, since they too could have such powers and not be colored: they might be little minds or brains. Having the power to elicit experiences of red will never add up to being red—merely to the ability to cause experiences thereof (almost anything can do that in the right circumstances). The condition is clearly far too weak.
So the Lockean theory of color renders color (a) invisible and (b) a property of the mind-brain. As I say, brutal.
Colors and Powers
According to Locke, colors are nothing but powers in objects to produce ideas in our minds. He writes: “What I have said concerning colours and smells, may be understood also of tastes, and sounds, and other the like sensible qualities; which, whatever reality we by mistake, attribute to them, are in truth nothing in the objects themselves, but powers to produce various sensations in us, and depend on those primary qualities, viz. bulk, figure, texture, and motion of parts; as I have said.” (Essay Concerning Human Understanding, Book II, Chapter VIII, section 14) There is, he tells us, no “resemblance” between these sensations or ideas and the objective ground of the power, as there is in the case of primary qualities, and without minds to interact with the powers there would be no color (etc.) in the world. To say that an object is red is just to say that it has the power to produce sensations of red in us: that is, colorless objects made of colorless minute particles happen to cause in us a certain type of sensation, and that is all there is to color—it has no mind-independent existence.
But two questions may be raised about this doctrine, appealing though it is. The first is that a given object has several such powers: it may produce sensations of red in one set of perceivers and sensations of green in another set (and so on for the other colors). It doesn’t have a unique idea-producing power but many such powers (it could even produce ideas like those produced by the other senses). Yet there is only one set of primary qualities underlying this multiplicity of powers. This prevents us from identifying the color with the primary quality basis, on pain of identifying the colors with each other (same basis for each power and hence sameness of color). It isn’t the power in the object that is fixing the color of the object but its relation to the minds of perceivers. Second, how could a colorless object have the power to produce sensations of color? Nothing about the object itself explains the power it has to excite color sensations, let alone specific color sensations. It is, we might say, chromatically impotent. It would be a type of miracle if primary qualities had the power to produce sensations of quite different qualities. The only sense in which objects have such powers is that minds have corresponding powers: the mind has the power, when interacting with colorless objects, to generate sensations of color—the power comes from it not the external object as such. The power of which Locke speaks is really a relational power not an intrinsic power. Intrinsically the object is powerless to produce color sensations; whatever power it possesses is conferred on it by perceiving minds. Locke should have said that colors consist in the power of our mind to impose colors on the world—powers in the mind not powers in objects. Does a square object have the power to produce sensations of a round object? Well, it can produce such a sensation if the perceptual system misfires, but it has no intrinsic power to do any such thing—as it has to produce a sensation of a square object. It just happens to cause (partially) a sensation of roundness; the real work is done by the perceiving mind—it has the power to respond with roundness perceptions to a square object. Similarly, colorless objects can elicit sensations of color, but only because minds are so set up that they can generate sensations of color in the presence of things that have no color. The external primary qualities play a minimal causal role, and considered in themselves have no power to produce sensations at all. Indeed, it is conceivable that there be no such objects and yet the mind has the power to generate the full panoply of colors from within its own resources (color sensations in a vat). In fact, we are already in a situation close to this in that we have colored mental imagery that is elicited by no external object—no primary qualities are triggering this kind of “perception”. The external object in the perceptual case merely triggers a pre-existing power of the mind; it is not the locus of the power to bring color sensations into the world. 
If we say that water has the power to dissolve salt, we mean that water has objective properties that explain how the power is exercised; but if we say objects have the power to cause color sensations, we can’t provide any such explanation. This is because objects are powerless in this regard; the mind is the origin of the power in question. Imagine a world in which there are simple objects having just two properties and yet these objects are perceived by minds as being rich and complex, endowed with (say) a thousand properties. It would be bizarre to suggest that the objects have the power to produce the full range of sensations available in this world—that power properly resides in the minds that exist in it. It would be quite wrong to say that the properties perceived are nothing but powers in the objects to produce sensations, with their impoverished two-property profiles. The objects have no such intrinsic power, though they have the weak relational power of being able to interact with minds that do have the power to perceive the full range of a thousand properties. In a way Locke undersells his own subjectivist position, which is that the mind is the origin of secondary qualities not the external world. At the least he should have distinguished between the weak sense of power and the strong sense, maintaining only that objects have only a weak power to cause sensations. Primary qualities, by contrast, have a strong power to produce sensations because of that “resemblance” he mentions, but secondary qualities are only weakly connected to the objective nature of external objects. They are connected in roughly the sense in which sugar has the power to taste bitter if the taster’s sense organs are deranged in some way, or in which red objects have the power to appear yellow if there is something wrong with your eyes. The relation expressed by “x can trigger y” is much weaker than that expressed by “x has the power to y”.
This matters because it affects the strength of subjectivity of Locke’s basic doctrine. If we identify colors with powers-in-objects, then we accord them a degree of objectivity not intended by the basic metaphysics; but if instead we identify colors with powers-in-the-mind, then we fully endorse the fundamental thesis that colors are purely subjective, i.e. originate in the mind and are then imposed or projected onto external things. Here is Locke in full flight: “The particular bulk, number, figure, and motion of the parts of fire, or snow, are really in them, whether anyone’s senses perceive them or no: and therefore they may be called real qualities, because they really exist in those bodies. But light, heat, whiteness, or coldness, are no more really in them, than sickness or pain is in manna. Take away the sensation of them; let not the eyes see light, or colors, nor the ears hear sounds; let the palate not taste, nor the nose smell, and all colours, tastes, odours, and sounds, as they are such particular ideas, vanish and cease, and are reduced to their causes, i.e. bulk, figure, and motion of parts.” (ibid, section 17). That use of “reduced” is perhaps ill advised, suggesting as it does that secondary qualities, and ideas of them, are reducible to primary qualities of external things, which would make them as real as primary qualities in general. But it is clear that Locke intends to maintain that colors (etc.) are mere subjective projections not at all inseparable from matter—they arise from powers of the mind not from powers of matter. It is only in a very weak sense that we can say that objects have the power to produce ideas of secondary qualities, as weak as saying that manna has the power to produce sickness and pain, or a spear has the power to be thrown. The truth is (according to Locke) that colorless particles interact with our colorless sense organs in such a way as to activate the latent power of the mind to generate colors in all their glory. The power to produce color sensations is a mental power not a power of material objects considered in their own right. Perhaps Locke was subliminally influenced by his opposition to innate ideas: for if colors originate in the mind, how can ideas of them be derived from perception of external objects? At any rate, one who sympathizes with Locke’s metaphysics of color has reason to dislike his official object-centered formulation of the doctrine. The powers that give rise to colors are in the mind not in the external world. 
 Much the same can be said about the dispositional formulation of color subjectivism: objects have many color dispositions and no object has such a disposition intrinsically. Rather, minds have dispositions to see the world as manifesting various colors—that is where the disposition originates. Objects are merely disposed to trigger such mental dispositions in the sense that they can trigger them in certain conditions. The ontological work is done by the mind not the world.
 None of this is to deny that matter might be the origin of the mind’s power to produce colors; it is just that the material objects of perception are not the locus of the power to bring colors into being. Put broadly, Locke (and his followers) are putting too much emphasis on the powers of objects and neglecting the vital contribution made by the mind.
Color and Causality
Color and causality don’t mix: causality doesn’t mention color and color is indifferent to causality. Shape is very different: shape always affects causal powers. Shape and causality are made for each other, while color and causality are complete strangers. This means that ordinary objects have two aspects—causal and non-causal. We know this from everyday perception: we see the way shape affects causality as objects interact, but we never see colors affecting objects causally. Objects don’t attract or repel each other in virtue of color; color doesn’t affect the laws of motion; objects don’t change the color of other objects in virtue of their color. This is why physics has no time for color; it simply isn’t a causal variable. Perhaps we can imagine a world in which color does exercise causal powers: objects move differently according to color; they have attractive and repulsive forces as a function of color; the color of one object can change the color of another if it gets close to that object. But this strikes us, rightly, as unintelligible: how could color exercise such causal influence (compare moral properties)? In any case, it isn’t so in our world; nor does this seem like an accidental fact about color. Color is epiphenomenal. This fuels projective views of color: the reason colors lack causal powers is that they are projected by the mind onto objects; they are not intrinsic to objects. Perceived color is a kind of illusion: colors don’t exist in objects but in the mind, and a distant mind can’t affect the causal powers of an object. If you experience a visual illusion, the properties attributed in the illusion won’t affect the causal powers of the object (the apparently bent stick in water won’t behave like a bent stick in its causal interactions). Nor does seeing-as affect the causal powers of an object according to the aspect seen. Color perception is like that, according to projectivism, so of course color is epiphenomenal: it isn’t even a constituent of external reality. But even a realist about color will concede that colors have no causal powers: they exist in objects but they make no causal difference to how objects behave. Figure, mass, and force make a causal contribution, but color is causally idle.
So much is generally (though not universally) accepted, if not always with complete equanimity. Why are colors there if they make no causal impact? Are they really in objects at all? The point I want to make, however, has not, to my knowledge, been stated: namely that colors so understood make trouble for the causal theory of perception (or maybe the causal theory of perception makes trouble for colors). That theory says that perception requires three conditions to be met: (i) the object has the property, (ii) the perceiver has the impression of the object having the property, and (iii) the object’s having the property causes the impression that it does.  There are refinements that need to be made, but it is generally accepted that the causal condition is at least a necessarycondition for veridical perception to occur. But colors have no causal powers, so how can they be seen? Colors can’t cause sense impressions in perceivers because they can’t cause anything: the color red, say, doesn’t cause sensations of red in perceivers by interacting with the rods and cones, since it has no causal powers. It is true that the surface of the object reflects light waves that cause disturbances in the receptor cells of the retina, but that is not what the color is—or else colors would have causal powers and be studied by physics. We can of course stipulate that “color” is to refer to such physical phenomena, but these phenomena are not colors-as-we-see-them—those things are causally inert. So colors in the ordinary sense cannot be the cause of impressions of color–yet we see them all the time. On the face of it, then, the causal theory of perception is false for colors, though not for shapes: you can see a property that does not cause you to see it. Colors are visual objects par excellence but they are not causes of visual sense impressions. If it were possible to see an object only as colored, then we would have the result that an object can be seen and yet have no causal contact with the perceiver. Or to shift to another type of secondary quality: if a piece of sodium chloride could be tasted only as salty, with no other quality perceived, then perception of an external physical object could occur in the complete absence of any causal contact with its manifest properties. For secondary qualities in general are causally impotent, and ex hypothesi they are the only ones being perceived in such a case. It would be logically possible to perceive all the objects of the external world and yet have no causal contact with those objects.
Of course that is not the only possible response: someone might maintain that colors are not perceived precisely because they have no power to be perceived, as the causal theory implies. Instead they are hallucinated as a result of photon bombardments; they don’t really exist in objects at all. There is thus no veridical perception of color. If this is felt to be ad hoc and implausible, we could try a third approach: colors are invisible. They exist in objects and we have impressions of them, but they are not seen at all: what we have here is a case of veridical hallucination. The object is red and it looks red, but because of the lack of causal connection it can’t be perceived—so it’s literally invisible. I don’t know of anyone who has adopted this view, and one can understand why: to say that colors exist in objects, and that we have impressions of them, but we don’t really see them, is radically counter to common sense. We would need some motivation for this combination of claims that goes beyond simply observing that the perception of color is incompatible with the causal theory of perception. For the natural conclusion is that color perception refutes the causal theory of perception, since we can see properties that don’t cause us to see them. Or is it that they have a magic power to whisk causation into existence when and only when a visual system passes by? My own conclusion is that color perception is a straight counterexample to the causal theory, even as a theory of the necessary conditions of perception (there are well-known problems about its sufficiency). The intuitive idea behind the theory is simply wrong; the theory is at best partially true. The simple fact is that you can see the colors of objects without their causing you to do so. 
 One might try to weaken the theory so as to require only that a suitably connected property be the cause of the sense impression not the color property itself—as it might be, the light waves correlated with the color. However, this runs into immediate problems such as fact that the seen color will not be caused by the color itself but by a distinct property, so why is the impression not a misperception of that property? And surely we don’t want to end up saying that the only true causes of sense impressions are basic physical properties, with the consequence that only such properties are really perceived.
Color and Perception
For color, to be is to be perceived: not so for shape. That was a central tenet of the modern philosophers. Color depends on perceivers for its existence, but shape does not. Thus it makes no sense to suppose that colors exist in a possible world and yet no one perceives them—not humans and animals, not God, and not the colored objects themselves. For what colors would they be? There is nothing to determine what color an object is except how it is perceived (in normal conditions by normal perceivers). The same is not true of shape: shape is determined by how the object behaves in relation to other objects, i.e. by its causal powers. For shape, to be is to be causal. There is something other than perception to fix the shapes of objects. But there is nothing other than perception to fix the colors of objects–hence the vacuity of the idea of a colored world devoid of any perceivers whatsoever. We can certainly subtract a sub-class of color perceivers from a world and leave color intact, but we can’t take allperceivers away and expect to be left with color in all its glory. Suppose colored objects all had eyes and could see their own color: we could remove human and animal perceivers, and even any divine perceivers there might happen to be, leaving only the sighted objects themselves; but we had better not remove the eyes of these remaining perceivers if we want to leave color intact. Nothing like this is true of shape, however, since the causal profile of objects can survive their not being perceived (it is “objective”). This is why people call shape a “physical” property and color a “mental” property: it is a matter of perceiver-dependence, or the lack of it. Most modern philosophers thought the necessary perceivers were human (or possibly animal); Berkeley thought they were human and divine; someone else might suppose that the objects themselves are the perceiving subjects of their sensory qualities. The common thread is that colors need perceivers, because their esse is percipi. Shapes, on the other hand, don’t need perceivers, because their esse is not percipi, but rather causal or mechanical or physical. This is the crux of the distinction between primary and secondary qualities, as it has been traditionally understood. Secondary qualities are the ones that are inextricably linked to mental acts of perceiving in such a way that perception is both necessary and sufficient for their existence (by normal perceivers in normal conditions, etc.). Without suitable perceivers, then, color has no ground of being. It is the same for other secondary qualities, perhaps more obviously so: no world has tastes and smells in it that lacks all perceiving subjects—human, animal, divine, or objectual. For what tastes and smells might these be? Tastes and smells don’t affect inter-object causal powers, so they have no ground beyond perception: to have a certain taste is to taste a certain way to perceivers—not to propel objects in a certain direction that interact with the tasty object.
Does this imply that secondary qualities are mental (subjective, psychological)? Not strictly, since they may be non-mental qualities that are fixed by mental facts: they might be a special type of primitive property that depends for its instantiation upon mental facts about perceivers. But (a) that would be a pedantic distinction in the absence of some principled reason for withholding the term “mental” from them; and (b) even granting the point we still have the conclusion that colors require mental acts of perceiving, which is all the metaphysician of color is really interested in (it will be sufficient for object mentalism certainly). True, we don’t normally call colors “mental” or “psychological” for boring conversational reasons (the implicatures are uninviting), but from a theoretical point of view there is nothing amiss with extending the use of the term in this way—since colors do depend on mental acts strictly so called. The important point is that colors (etc.) contrast with shapes (etc.) in their relations to perceivers, with the former presupposing them and the latter quite indifferent to them. We can simplify by saying that secondary qualities are mental and primary qualities are not mental. Then we can derive appropriate conclusions from this distinction, notably that colors need perceiving subjects and shapes don’t. Of course, if we were to claim that colors are reducible to wavelengths, then the distinction would collapse and colors would not depend on perceivers ; but I am assuming here that this is wrong and that the choice is between a sui generisclass of non-mental properties and inclusion in the class of mental properties. And the point I am making is that for colors and other secondary qualities, to be is to be perceived by some perceiver or other: take away all perceivers and you take away color. Or better: if there had never been any perceivers, there would be no colors (tastes, smells, etc.)—just as, if there had never been any organisms, there would be no poisons or fearsome objects or healthy life-styles. And which colors an object has depends on how it is perceived: there is no experience-transcendent criterion of color distribution. The same is not true of primary qualities, since they play a role in the causal workings of the world as described by physics.
We can imagine someone jibbing at the idea that pains are aptly described as mental on the grounds that pains are located in parts of the body and hence are “physical” (“mental” pain is more like inner anguish). The same might be said of perceptual sensations, which are located in or near the sense organs. This fastidious thinker reserves the word “mental” for thoughts, which seem to occur in the inner sanctum of the self. One can appreciate the motivation for this policy of verbal purity, but it doesn’t affect the point at issue: even if we accept it, we can still assert that pains and sense perceptions require a perceiver in order to exist, along with a mental act of apprehension. So they are “mental” by association. They are not like states of the body that require no apprehending subject in order to exist. Even if pains and sense perceptions are not rightly described as mental, they still presuppose a perceiving subject, and that is the central point at issue. Likewise for colors, tastes, etc.: even if they are declared sui generis—neither mental nor physical—we still have the conclusion that they are dependent on a psychological subject. Supervenient facts don’t have to be of the same type as the facts on which they supervene, but they still presuppose those facts—they can’t exist without them. From the point of view of object mentalism, then, it is all one whether we call colors mental or assign them to a separate category; all that matters is that they are perception-dependent. The question at issue is the identity of the relevant perceivers—whether human, animal, divine, or the objects themselves.
The point on which Berkeley was particularly insistent is that mental qualities cannot inhere in a purely material substance, as many had supposed. If color is mental (or dependent on the mental), then it needs a distinctively psychological subject: it can’t just be the same material substance that primary qualities happily inhere in. So when an object is both cubical and red it needs two supporting substances, one for its primary qualities and one for its secondary qualities (a self in short). If we retain the ideas of primary qualities and material substance (contra Berkeley), then we need to add a suitable substance for the secondary qualities, construed as mental, viz. a perceiving subject. The question then is what or who this subject is—human and animal minds, the divine mind, some sort of immanent cosmic mind, or the mind inherent in the object that has the quality in question. But there should not be much dispute about the conception of secondary qualities that powers this debate, i.e. their essential connection to perception. 
 For someone who holds that the world could contain all the secondary qualities it now contains in the complete absence of anyone to perceive them, the obvious question is what might confer these qualities on the world. Surely these qualities reflect the survival needs of organisms and are not simply found to exist in the world ab initio. Could it be the case that all organisms misperceive the real colors and tastes of things, these being determined quite independently of how the world seems? Of course, the physical basis of such qualities could exist in the absence of perceivers, but could colors-as-we-perceive-them so exist? Is the redness of red something that exists independently of the appearance of red to perceivers? What if one group of perceivers sees tomatoes as red and another sees them as green—is one right and the other wrong (or both are wrong)?
Object Mentalism and Philosophy
What impact would the truth of object mentalism have on the philosophical landscape? For expository reasons I shall speak as if it is true, though we could also conjure a possible world in which it is stipulated to be true and consider philosophy as it exists in that world. So: suppose that all objects (except perhaps the very small) have mental properties in the form of secondary qualities and also contain a perceiving subject, and let’s limit ourselves mainly to speaking of colors. Red objects, say, have the mental property of being red and they also perceive this property in themselves. Then the first consequence we can draw is that there are two sorts of mind, which I will call the internal mind and the external mind. There is the internal mind generated by the brain, which is private and imperceptible, not open for all to see. But there is also the external mind that is perceptible on the very surface of objects, since colors are perceptible. It is true that the perceiving of red by a red object is not likewise perceptible, and it may not much resemble what seeing red is like for us; but there is no denying that if colors are mental properties then we can perceive mental properties in objects. This was tacitly accepted by philosophers of the modern period who distinguished primary and secondary qualities, though I don’t recall any of them noting it explicitly. Someone who believes that color is a projection of inner mental states, and that we see color, is committed to the view that we can see mental states—though the mental states are really possessed by the perceiving subject not the object out there in the world. Once we add that the perceiver is actually the object itself we have the result that the mind of the object is a perceived mind. And note that the brain is a perceptible object, so it has two minds: the internal mind we are familiar with by introspection, containing perceptions of color among much else, and another mind corresponding to its own secondary qualities—color, taste, smell, etc. The brain perceives itself with this mind, though our internal mind has no access to it. Other objects (including other bodily organs) have an external mind but not the internal mind we know from introspection. They do have their own type of internal mind, however, constituted by perceiving their sensible qualities, but this mind lacks much of what brain-based internal minds routinely possess. Still, the object does have a mind that is partly public and easily perceived: the concept of the mental is thus not inherently the concept of a private sphere.
Secondly, we now have an extra mind-body problem: how does the mind of an object relate to the “body” of an object? Specifically, how does color relate to the physical properties of an object? Here we can envisage the usual options: perhaps the color is merely projected from elsewhere so that it doesn’t exist in the object at all (compare the idea that the mind is just a “stance” we can choose to adopt); or it is identical to the properties of light discoverable by science (type or token identity theory); or property dualism is true, with or without supervenience; or substance dualism is true and there are really two objects there, the bearer of primary qualities and the bearer of secondary qualities, one material and the other immaterial; or perhaps talk of color is just so much prescientific gibberish destined to be eliminated from our world view. It is noteworthy that these options so closely mirror the positions familiar from discussions of the mind-body problem for the internal mind, suggesting that objects do indeed have a kind of mind. Presumably consciousness in some form will be involved in the workings of the external mind, though it may be a form of consciousness alien to us—I picture it as a kind of low-grade murmuring. This consciousness must have emerged from properties of matter that precede the existence of consciousness as it exists in the form of color etc., since it is doubtful that elementary particles and associated forces possess such qualities.  So there will be a hard problem about external conscious minds too, and possibly an irresoluble mystery. In any case, there is a mind-body problem under object mentalism, very similar to the traditional mind-body problem.
Third, our concept of mind is put under strain by the doctrine of object mentalism. The concept we possess is clearly shaped by our own specific form of mind—the conscious adult human mind we know by introspection. As soon as we venture beyond this, as we clearly must, we run into difficulties, since not all minds conform to this paradigm (for us). What about the unconscious mind, or the minds of animals zoologically remote from us, or the minds of aliens, or the enteric mind, or the mini-minds of the panpsychist? The concept of matter is not dissimilar: it no doubt originates in middle sized dry goods but we find it necessary to extend it to types of matter not normally encountered by us—the very small, the quantum-theoretic, forces and fields, dark matter, etc. The concept quickly runs out of descriptive or intelligible content—yet we keep on extending it. Applying the concept of mind to objects of all kinds, as the object mentalist does, certainly runs the risk of over-extending it, but we need some concept with which to register certain clear similarities and differences. It then becomes a pointless verbal question whether our words “mind” and “mental” properly fit the facts we are trying to capture (similarly for the word “physical” in trying to capture the facts uncovered by physics). We might decide to devise two concepts of mind in order to aid clarity and avoid confusion: the internal mind and the external mind, the subjective mind and the objective mind. Our vocabulary is limited and clearly inadequate, but we have enough to group things together intelligibly enough. In our own tradition terminology has shifted from “spirit” and “soul” to “mind” and “self” under pressure from various cultural and intellectual developments; the same thing could happen in the future if object mentalism gains a foothold. 
Fourth, in respect to metaphysics we now have a new option to play with: we have not just materialism, idealism, and dualism, but also a new type of generalized mentalism. This mentalism recognizes mind in many more places than alternative views, as various forms of panpsychism also do, by attributing it to ordinary objects in virtue of their secondary qualities; but it doesn’t descend into out-and-out idealism (though it is consistent with that and might be so extended). We could call it “modest idealism”. It certainly has an affinity with Berkeley’s position and relies on some of his insights; it diverges in not bringing in God and not applying itself to primary qualities. Mind turns out to be much less localized than we supposed, much more a general fact of nature; or rather, matter has less hegemony than we have been schooled to think. In fact, there is really no such thing as matter under the object mentalism conception—that is, a substance quite devoid of all subjectivity (this was Berkeley’s definition of matter or “corporeal substance””). Descartes was wrong to carve out an ontological realm from which mind has been completely expunged, in which secondary qualities are assigned to the perceiving mind of humans and other animals. Once these qualities are attributed to objects themselves the moderns’ conception of matter loses application, just as Berkeley argues. This destroys dualism as much as materialism, since there is nothing for pure matter to be. What we have is an inextricable combination of “mental” and “physical” qualities found instantiated together: that is the nature of concrete reality. The opposition between matter as wholly non-mental and mind as contrasted with this material realm collapses. We have been in the grip of the idea that objective reality consists of pure material substance with nothing mental about it, while all along the obvious existence of objects possessing secondary qualities has contradicted that idea. It is our conception of matter that has been at fault—and by “our” I don’t mean the human race but assorted theoreticians with various intellectual and scientific agendas, Descartes being chief among them. Mechanism is the ultimate culprit—the attempt to carve out a conception of reality that leaves mind behind. This is that desiccated, abstract, conjectured, mathematical, merely extended, insensate substance that was supposed to form the subject matter of physics; but there is no such substance, since objects are really colored (etc.). Nor is this a problem for physics as a science; physics simply deals with certain aspects of objects. It is a problem, however, for a certain philosophy of physics—one in which external reality is completely devoid of anything recognizably mental. There is no such thing as that and hence no such thing as Cartesian matter. The metaphysical picture bequeathed to us by seventeenth century thought is fundamentally flawed (according to object mentalism), and in just the way Berkeley diagnosed (his own positive theory is another matter). Matter in that sense is a myth. 
Finally, the opposition between mind and world has to be rethought. The mind is certainly not “in the head” if objects have minds too; and objects are not “in the world” if that means they lack all mentality. We can see mind in the world, and the world can see its own mind: mind is “out there”. Our internal mind may or may not be “in the head” but the external mind certainly isn’t—though it might be in its own head (if it had one). We have to reformulate the whole way we talk if object mentalism is true, because of its opposition between mind and world: we need to know what kind of mind is at issue, since one kind of mind is literally part of the world. The internal mind is really just one type of mind existing in the midst of innumerable other minds. How these two types of mind are related then remains an outstanding question; and we can’t just assume that the internal mind is fundamental. Maybe that has been our mistake all along. Maybe the world began with external minds and gradually worked up to internal minds, themselves very various. 
 There could be a form of panpsychism that claims that elementary particles have “proto color” from which arises color-as-we-perceive-it; so electrons and so on would not be completely devoid of color, after all.
 Have we not discovered, as history has worn on, that our initial concept of mind was hopelessly anthropocentric and parochial? Some people didn’t even think animals have minds! Hindsight recommends keeping an open mind about the extension of the predicate “mind”.
 Maybe it wasn’t that human minds created color, taste, etc. but that these qualities created human minds: the ultimate source of human and animal minds is not primary qualities of matter but secondary qualities. It’s worth pondering.
Let’s suppose that object mentalism is true—the doctrine that every object has a mental life. I mean this doctrine as derived from the thesis that all secondary qualities need a psychological subject: since such qualities are mental they must be perceived, so everything having them is a perceiver of some sort.  My concern here is with the consequences of this view for the nature of planet earth: what does it tell us about the mental status of that planet? Well, it immediately follows that earth has a mind (or many minds), since it has a multitude of secondary qualities: earth perceives all its colors, tastes, smells, sounds, and tactile qualities (though not necessarily its primary qualities). But earth is a very large complex object with an enormous variety of qualities, so that should affect the kind of perceiving mind it has. It may be expected to have a mind commensurate with its size and complexity, especially its rich array of secondary qualities. It should be a larger mind than the moon’s mind, or even the sun’s mind (which doesn’t have a wide range of different sensory qualities). I would estimate that it possesses the largest mind of any celestial object we know of. The earth does an enormous amount of perceiving. We may not know much about what the earth’s mind is like, but we can be assured that it is capacious—though focused on its own appearance. It is a gigantic kaleidoscopic sensorium.
I mention this consequence of object mentalism because I think it might help with ecological ethics. For we have had trouble marshaling much moral concern for planet earth, on the assumption that it is just an insensate rock (with some sentient beings at and around its surface); and recognizing that earth has a complex mind might help us generate a more robust moral concern for its fate. If sentience of some sort is the criterion for moral concern, then the earth qualifies, according to the doctrine of object mentalism. The earth has a mind of its own and hence deserves moral consideration. It may not be an organism, as some have supposed, but it is a repository of mental states, along with an appropriate perceiver. This is to assume that the objects that make up the earth are unified in some way, so that we are not dealing with a mere aggregate of individual sensing objects; but this hypothesis can’t be ruled out, so it may be that the whole earth has a mind not just its parts. In any case, there is a lot of mind in the earth, whether unified or not. This may help us treat the earth with more care and respect. 
 The expanding circle of morality is ever widening and it is past time we widened it yet further to include the planet we live on. We might even bring it under a utilitarian ethic by postulating that some of earth’s sensations are connected to pleasure and pain, particularly in the case of sensations of taste and smell, but also with respect to color and sound. Our sensations of secondary qualities are intimately connected to pleasure and its opposite. Remember it was once thought fanciful to attribute minds to “brutes”. The concept of mind has politics built into it. Is in the interests of certain groups to deny that the earth is anything but a mindless soulless rock, as it was in the interest of certain groups to deny that animals have minds or souls (ditto selected peoples).