MIND-DEPENDENCE IN BERKELEY AND THE PROBLEM OF PERCEPTION Umrao Sethi (Forthcoming in Australasian Journal of Philosophy) Abstract: On the traditional picture, accidents must inhere in substances in order to exist. Berkeley famously argues that a particular class of accidents-the sensible qualities-are mere ideas; entities that depend for their existence on minds. To defend this view, Berkeley provides us with an elegant alternative to the traditional framework: sensible qualities depend on a mind, not in virtue of inhering in it, but in virtue of being perceived by it. This metaphysical insight, once correctly understood, gives us the resources to solve a central problem that still plagues the philosophy of perception: the problem of how, given the power of the mind to create phenomenally rich experiences, ordinary perception can nonetheless be said to acquaint us with the mind-independent world. Keywords: problem of perception, Berkeley, inherence, mind-dependence, over-determination §1. Introduction In Berkeley's Puzzle, John Campbell offers two descriptions of what it is like to experience a phosphene – an experience that is induced by exerting pressure on a closed eyelid. Campbell writes [Campbell and Cassam 2016: 10]: (1) It is just a denial of reality to say there is nothing there that is yellow, square and moving. That is the only vocabulary we have to describe what the subject is experiencing...you are not talking figuratively when you say that the thing is a vibrant yellow. (2) It's crazy to say there is something there that is literally yellow, square, and moving. We can search all of space and time and there is nowhere to be found anything literally occupying space that has these characteristics. There is nothing that is yellow, square and moving. These descriptions serve equally well for a range of delusive experiences-including phosphenes, after-images and full-blown hallucinations-in which we seem to have a vivid experience of sensibilia without there being any material object of awareness that has the sensible qualities we seem to be experiencing. In an experience of a yellow phosphene, there is no physical object that one is aware of that is yellow.1 So the standard explanation of why one seems to be confronted with an instance of yellowness-namely, because there is a yellow object being perceived-is not available. Given this fact, most philosophers endorse the second intuition expressed above and conclude that one cannot in fact be confronted with yellowness; instead, they insist, one merely seems to be so confronted. Just as a full- 1 Cf. Phillips [2013] for an account of after-images as illusions involving light phenomena in the physical world. Mind-Dependence in Berkeley 2 blown hallucination misleads a subject about the presence of a mind-independent object, this broader class of delusive experiences misleads subjects about the presence of instances of sensible qualities as well. Such philosophers typically go on to provide an explanation of why it seems to the subject as if there is an instance of yellowness present in one of three ways: by appeal to perceptual representation, qualia or uninstantiated universals. On the third strategy, while we are not aware of concrete instances of yellow when hallucinating or experiencing a phosphene, we are nonetheless aware of the uninstantiated universal yellowness (see Johnston [2004]). While this view acknowledges the importance of positing an actual awareness of sensible qualities to explain the phenomenology of such experiences, it remains mysterious how an awareness of uninstantiated universals helps explain the fact that yellowness seems present at a particular point in time two feet in front of my nose. For regardless of the particular view of universals one adopts, we must concede that an uninstantiated universal, if it exists at all, can only be an abstract entity that exists outside the spatiotemporal world. Not only is it unclear what it would amount to for us to be perceptually aware of such universals; even if an account were to be given, it seems unlikely that it could provide a satisfying explanation of the seeming presence of concrete instances of those universals. (For criticism of a view on which we are aware of such abstract objects, see Pautz (2007) and Kriegel (2011). By contrast, an appeal to intrinsic, non-representational properties of experience-qualia-may explain why it seems to the perceiver as if she is aware of instances of qualities, as opposed to universals, but fails to explain why it is instances of color or shape that she seems to be aware of. Importantly, qualia are not the ordinary sensible qualities that physical objects instantiate, but, rather, internally determined properties of the perceiver (or of her experience) that stand in some extrinsic-usually causal-relation to the qualities of physical objects. (Thomas Reid is thought to be an early modern proponent of such a view. For contemporary versions of the qualia view, see Shoemaker [1990] and Block [1997].) So, while this strategy does justice to the concrete character of our perceptual phenomenology by insisting that it must involve the actual instantiation of qualitative properties, it fails to explain why being in a state that instantiates these internally determined 'qualia' makes it seem, from a perceiver's subjective point of view, that she is aware of qualities of external-world objects like color, smell, sound or shape.2 2 A projectivist addition to a qualia account would have the right structure of an explanation of the seeming facts, but projectivism is infamously hard to develop. Mind-Dependence in Berkeley 3 The most common strategy, then, is one that appeals to perceptual representation (see Anscombe [1965]; Harman [1990]; Byrne [2009]; Siegel [2010]). The essential move is as follows: Even though the perceiver is not aware of an instance of yellowness in a phosphene experience, it seems as though she is because she is in a state that represents yellowness. It is true that delusive cognitive states are deftly handled by an appeal to representation. I can believe that the tomato you bought is yellow even if it is in fact red and I can judge that the table in the seminar room is rectangular even if it is in fact square. Believing or judging something is a matter of representing the world to be some way that it may or may not be. But while we can surely understand how one can believe that the world is some way that it is not, it is difficult to satisfactorily extend the representationalist strategy to the case of perceptual experience. For the supposed yellowness of the tomato or rectangularity of the table is just not present before the believer's mind, when she forms a false belief about those objects, in the vivid way that yellowness is present before a perceiver's mind when she experiences a yellow phosphene. In other words, what makes the character of our experiential states distinctive is precisely that the qualities we perceive seem actually present before the mind, and not merely represented. Campbell's claim that 'it is just a denial of reality' to reject the actual presence of yellowness in a phosphene experience would have been far less plausible had he been discussing false beliefs. So while representationalists can straightforwardly explain the theoretical possibility of inaccurate mental states, they have a much harder time explaining why sensory representations, despite being inaccurate, make their objects seem so vividly present to the perceiver.3 Of course, more needs to be said to provide an exhaustive consideration of these approaches; I have only indicated the kind of prima facie challenge that they face in explaining the persisting strength of the first intuition described above. In the following section, I sketch an alternative approach that 3 Representationalists typically respond to this observation by positing a distinctive sensory kind of representation that is meant to do justice to the unique way in which qualities are present in perception. See, for example, Pautz [2009]. But merely appealing to a special kind of representation that can secure the vividness of perceptual experience is not to explain its possibility. Given that the notion of representation was not originally employed to explain the phenomenology of inaccurate cognitive states like belief-if they have phenomenology at all-there is no existing model for how the notion can be leveraged to explain the phenomenology of experience. This is not to say that the project is impossible, but simply to point out a significant gap in most extant developments of the view. See Millar [2014] for an attempt to explain the distinctive way in which qualities seem present in sensory experience (what he calls 'phenomenal presence') from within a representationalist framework. Mind-Dependence in Berkeley 4 allows us to straightforwardly accept the intuition that delusive experiences present us with actual instances of sensible qualities.4 §2. The Nature of Sensible Qualities There is a long tradition, going back at least to Aristotle, of distinguishing substances from all other entities. According to this tradition, substances are, in some important way, fundamental, while qualities and relations are, by their nature, derivative or dependent. In the Categories, Aristotle defines substance as 'that which is neither said of a subject nor in a subject' (Ackrill 1963: 2a11-13). In contrast, 'all the other things are either said of the primary substances as subjects or in them as subjects. So if the primary substances did not exist it would be impossible for any of the other things to exist' (ibid., 2b4-6, my emphasis). The examples Aristotle provides-a particular piece of grammatical knowledge and a particular whiteness-are 'accidents', or, in modern parlance, instances of properties. The basic claim here is a familiar one – a particular instance of whiteness can exist only if there exists a substance for that whiteness to inhere in. Inherence is the metaphysical relation that a property-instance typically stands in to the substance that is its bearer. When a property-instance inheres in a substance, we can predicate that property of the substance in question. Note that this claim is distinct from the anti-Platonic claim that whiteness, as a universal, cannot exist without the existence of substances that instantiate whiteness. My focus here is on the existence conditions on particular instances of properties. The key claim, for our purposes, is that particular property-instances, or accidents, secure their existence by inhering in substances. In order to define the kind of dependence that accidents have on the substances that they inhere in, I will make use of some tools developed by Kit Fine and others in recent work on ontological dependence [Lowe 1994; Fine 1995; Koslicki 2012]. Fine argues for a non-modal, asymmetrical notion of ontological dependence on which an entity x is ontologically dependent on an entity y iff y is a constituent of the essence or nature of x. For example, the singleton set containing Socrates as its sole member is ontologically dependent on Socrates because the essence of a set is defined in terms of its 4 In this paper, I will only consider delusive perceptions that lack any material objects of awareness. There are also illusions in which the perceiver is aware of a material object but misperceives one or more of its properties. The class of illusions is highly heterogeneous, and a full treatment lies outside the scope of this paper, but in brief: I am sympathetic to a view on which many so-called illusions involve a perceiver being aware of how an object looks, where these looks are themselves given a robustly objective analysis (see, for example, Schellenberg [2008], Martin [2010], Brewer [2011]). There are also some illusions that are better analyzed as partial hallucinations, to which the account of hallucination developed below directly applies. Mind-Dependence in Berkeley 5 members. Since the essence of Socrates is not defined in terms of any sets of which he might be a member, despite the true modal biconditional that Socrates exists iff the singleton set does, the relation between Socrates and the singleton set containing him as a member is asymmetrical. It is clear that the relation between property-instances and substances is likewise asymmetric. A property-instance depends, for its existence, on the substance that it inheres in; but a substance does not depend, for its existence, on any of the particular property-instances it supports (even if it depends on having some property-instances or other).5 It is also clear that a property-instance must inhere in a substance in virtue of its nature; that is, in virtue of what it is to be a property-instance. This aspect of the view is clear already in Aristotle, who took the definitions of the Categories to be carving out fundamentally distinct kinds of beings. So the Finean notion is appropriate for our purposes and can be adapted as follows: DependenceINH: A property-instance, f, dependsINH on a substance, a, iff □f (if f exists, a exists and f inheres in a). [where □x is a primitive operator that stands for 'it is true in virtue of the nature of'.] I want to suggest that it is an adherence to this framework, on which property-instances require a substance in which to inhere, that leads us to reject the first of Campbell's two intuitions described above. In ordinary cases of color perception, the instances of color that we are aware of do have physical bearers. But in the case of a phosphene or hallucination, we seek out a bearer for the yellowness that we seem to be aware of and find no suitable candidate. And so, we feel compelled to deny that there could be any real instance of yellowness present. As we have already observed, there is no suitable physical object to serve as the bearer of the colors and shapes that seem present. As Campbell writes, 'we can search all of space and time' and fail to find any physical thing that is yellow and suitably placed to explain our experience of yellowness. Furthermore, we cannot appeal to a phosphene or a hallucinated object as the bearer of yellowness either. We have now made clear that the relation between a quality-instance and its bearer is an asymmetric relation of dependence. This means that the bearer must be ontologically prior to the instance itself. But surely a phosphene, after-image or hallucinated object is nothing over and above its sensible quality-instances, and so it cannot explain the existence of these instances. One might try to hold on to Campbell's first intuition by insisting that the mind is the bearer of the yellowness that we seem to be aware of. Just as much as yellowness seems present in a phosphene 5 Here, the focus is only on non-essential property-instances (as is typical for 'accidents'). Mind-Dependence in Berkeley 6 experience, its presence seems connected to the perceiver. The perceiver is clearly having this experience because of the state of her perceptual system, not because of the way the external world is. Reflection on experiences of this sort have led some philosophers to conclude that sensible qualities are in fact mind-dependent and require minds to bring about their instantiation, not worldly objects. At this stage, we need to ask what it could mean for sensible qualities to be ontologically dependent on the mind. On the traditional framework, instances of sensible qualities exist in virtue of inhering in substances. If this is the conception of dependence we rely on, the thesis of mind-dependence amounts to the claim that the bearers of sensible instances are not material substances, but minds. So in place of the yellowness of a lemon or the roundness of a peach, we must speak of the yellowness and roundness of minds, or perhaps of experiences. But this interpretation has it that the mind, or an experience, is itself yellow in color, garlicky in odor or sweet in taste; that my mind or an experience is itself literally square when I look at a chessboard. These consequences are surely absurd and hard to make sense of. (See Sethi [forthcoming] for further discussion of these options]. Recognizing the untenability of these various options naturally leads one to the conclusion that yellowness just cannot be instantiated in a phosphene experience. And this returns us to the philosophical strategies described above – to deny the actual existence of any such instances and to try, instead, to provide a compelling error theory as to why such instances nonetheless seem present. I want to suggest that this narrative relinquishes the first intuition too quickly. This is because we can in fact make sense of how a sensible instance can exist even in the absence of any material or mental bearers. What we need to do is give up the traditional framework which construes the ontological relationship between substances and accidents as one that involves inherence. To spell out the alternative conception of mind-dependence I have in mind, I want to turn briefly to the work of Berkeley, one of the most radical proponents of the view that all sensible qualities are mind-dependent.6 In his defense of idealism, Berkeley infamously denies the very existence of material substances, arguing that the only genuine substances that exist are minds. Despite his idealism, though, Berkeley insists that he has left the world that we know about through perception-the world of colors, shapes, smells and tastes-untouched. This is what, allegedly, makes his view compatible with common sense. One might be surprised by the combination of these two claims. How is it possible for the sensible world to exist in the absence of any material substances? One might think that it is material substances 6 Many trope theorists reject the traditional framework too and treat property-instances as independent existences. I will not consider this strategy in this paper. Mind-Dependence in Berkeley 7 that are colored, shaped, odorous or tasty. If matter does not exist, there is no home left for the sensible. It is Berkeley's answer to this question that makes him particularly relevant to our discussion of delusive experiences. For, even though we are unlikely to follow Berkeley in denying the existence of material substances, we are nonetheless confronted by a class of delusive experiences in which we seem to be presented with sensible qualities, despite the conspicuous absence of any material bearers. In understanding how Berkeley secures the reality of particular sensible accidents in an immaterial world, we can, perhaps, do justice to the phenomenology of the class of delusive perceptions we are interested in. In the passage below, Berkeley explicitly considers and rejects the reading of mind-dependence as inherence in the mind-recognizing the absurdity of that picture, as described above-and then goes on to offer us an alternative (Principles, §49): It may perhaps be objected that if extension and figure exist only in the mind, it follows that the mind is extended and figured, since extension is a mode or attribute which (to speak with the Schools) is predicated of the subject in which it exists. I answer, those qualities are in the mind only as they are perceived by it – that is, not by way of mode or attribute, but only by way of idea, and it no more follows that the soul or mind is extended, because extension exists in it alone, than it does that it is red or blue, because those colors are on all hands acknowledged to exist in it, and nowhere else.7 Here, Berkeley suggests that what makes sensible qualities mind-dependent is not that these qualities inhere in the mind, but rather that they are perceived by the mind. From the very start of the Principles, Berkeley writes that 'the existence of an idea consists in being perceived' and that this is what it means to say that ideas are 'in minds' (§2). Given that sensible qualities are ideas, it straightforwardly follows-and Berkeley explicitly confirms this in passages like the one cited above-that what it is for sensible qualities to be in the mind is for the existence of these qualities to depend on being perceived by a mind. If we take Berkeley at his word, he is offering us an elegant and exciting metaphysical proposal. On his proposal, the existence of an instance of yellowness does not require any substance-material 7 Some commentators have argued that this passage is compatible with an inherence view of mind-dependence. See for instance, Allaire [1963], Cummins [1963], Hausman [1984]. For proponents of the alternative reading I present here, see Stoneham [2002]; Ott [2006]; Bettcher [2007] and Cummins [2007]. Mind-Dependence in Berkeley 8 or mental-to serve as the bearer of yellowness. Instead, an instance of yellowness requires, for its existence, a perceptual act, which has as its object this instance of yellowness. So, Berkeley's infamous maxim esse est percipi-'to be is to be perceived'-provides a literal statement of a distinct conception of how instances of sensible qualities can come to exist. Perception, for Berkeley, is an ontological relation, one that is capable of bringing instances of sensible qualities into existence: DependencePER: A property-instance, f, dependsPER on a substance, a, iff □f (if f exists, a exists, a is a mind, and f is perceived by a). Once we recognize that the mind explains the existence of an instance of yellowness not by bearing it, but by perceiving it, we see how the sensible world can be left untainted by Berkeley's idealism: the sensible qualities that constitute that world are secured not by relations of inherence, but by acts of perception. Importantly, Berkeley's idealism does not violate common sense by moving the colors and shapes literally inside the head, transforming them into mere modifications of minds. A quality that depends on being perceived by the mind need not be located where the mind is. Rather, we now have the room to insist that these sensible qualities, although mind-dependent, can nonetheless exist out there-external to the mind-in the spatiotemporal world.8 Crucially, we can also utilize Berkeley's insight to make sense of the delusive experiences we focused on in the introduction. In a phosphene experience or hallucination, the mind can secure the existence of actual instances of sensible qualities without those qualities needing to have any substantial bearers. We can be aware of an actual instance of yellowness even though we do not perceive any thing (in the substantial sense) that is yellow. We perceive an instance whose existence depends on the perceiver's mind.9 8 Berkeley's idealism may impugn the ontological status of space and time themselves and so he may deny that sensible qualities being in space and time implies that they are external to the mind in any robust sense. My point here is that his notion of mind-dependence is compatible with mind-dependent qualities being literally external to the mind by being spatially located in the world. Berkeley also states that sensible qualities are external to human minds in so far as they depend on God (see, for example [Principles §90; Three Dialogues, 250]), but this notion of externality to a particular mind is not relevant for our purposes. 9 This reading of mind-dependence also explains why delusive visual experiences present sensible qualities as in space and time (and, as the next section will demonstrate, how the mind can secure the existence of an instance that simultaneously inheres in a material object). One might think that Berkeley would deny this characterization of visual experiences given his insistence that strictly speaking, 'I see nothing but light and colors, with their several shades and variations' [New Theory of Vision §130] and that 'distance, of itself and immediately, cannot be seen' (ibid. §2). But see Atherton [1990] and Copenhaver [2014] for a reading of Berkeley on which we can visually (though non-immediately) perceive spatial features like distance and can therefore see colors in space. Mind-Dependence in Berkeley 9 At this stage, one might wonder whether the distinction between dependenceINH and dependencePER isn't merely terminological. Berkeley repeatedly paraphrases the construction 'in the mind' with the expression 'perceived by the mind'. Indeed, this has led some interpreters of Berkeley to suggest that 'since sensible objects inhere in a mind in the sense that they are perceived by it, "inhere in" may be replaced by "be perceived by"'10 [Allaire 1963: 229]. Even Michael Ayers, a strong critic of reading Berkeley as committed to an inherence model of dependence, concludes that ideas that are perceived by a mind 'inhere and must inhere in what perceives them' [1970: 41]. But treating perception and inherence as interchangeable notions obscures important philosophical distinctions. First, inherence in a mind does not guarantee perception by a mind – the property that my mind has of being awake for some exact number of minutes could be said to inhere in the mind but need not be a property that is perceived or known by the mind.11 Similarly, perception by a mind does not guarantee inherence in it. For, surely, on any commonsensical understanding of perception, perception by a mind is perfectly compatible with inherence, not in a mind, but in a material object. Importantly, even once we have Berkeley's technical notion of dependencePER in view, we still have no reason to conclude that perception by a mind entails inherence in the mind. Unless we are provided with further argument that the only way in which a substance can secure the existence of an accident is for the accident to inhere in the substance, we should not accept the entailment from perception to inherence, even when the relation of perception is taken to be a form of existential dependence. More importantly, the failure to disambiguate three distinct notions-a generic form of ontological dependence, the specific relation of inherence that accidents stand in to their bearers, and the relation of perception that accidents stand in to conscious minds on Berkeley's view-has farreaching consequences. We have already seen that we can make sense of how instances of sensible qualities can show up in delusive experiences without endorsing the unwanted implication that the mind is literally the bearer of the colors and shapes that we are experiencing. More surprisingly, though, once we recognize that Berkeley's notion of perception is to be understood as an alternative to the traditional notion of inherence, we see that minds and material substances do not play competing roles in explaining the existence of sensible qualities, even in the case of a particular instance of a sensible quality. That is, one and the same instance of yellowness, say, can have its existence guaranteed 10 Winkler [1989: 192] also treats 'is perceived by' as a 'less learned' formulation of 'inheres in'. 11 Though given Berkeley's critique of the very notion of inherence, he likely would reject the possibility of a property inhering in a mind without being perceived by it. Mind-Dependence in Berkeley 10 both in virtue of inhering in a material substance and in virtue of being perceived by a mind.12 This possibility, I will go on to argue, offers us a previously unconsidered solution to the age-old problem of perception – the problem of how, given the power of the mind to create phenomenally rich experiences, ordinary perception can nonetheless be said to immediately acquaint us with the mindindependent world. We can treat the particular instances of sensible qualities that we are aware of in ordinary perception as instances whose existence is doubly secured, both by the minds that perceive them and by the material objects in which they inhere. Such over-determined instances-despite the fact that our minds suffice for their existence-are genuine features of the mind-independent world: they continue to inhere in their material bearers even after our perception of them comes to an end. §3. Over-Determination and the Problem of Perception §3.1. Ontological Over-Determination The key insight is this: given that Berkeley's notion of perception is neither identical to nor implies inherence in the mind, a property-instance that is perceived by the mind can simultaneously inhere in a material body. In other words, perception by a mind, as a form of existential support, does not compete with, or rule out, inherence in a material body. It might initially seem that the two notions do compete. We have two notions of existential support here, and each is a form of full support. On the traditional view, all that is required for a propertyinstance to exist is for it to inhere in a substance. Similarly, according to Berkeley, all that is required for a property-instance to exist is for it to be perceived by a mind. But, if inherence in a body fully explains, or is sufficient for, the existence of a particular instance of yellowness, how could that very instance also have its existence explained by a mind's perception of it? Likewise, if perception fully explains the existence of a sensible instance, what role could inherence play? One might conclude that inherence and perception could only amount to competing explanations for the existence of a particular instance of a quality. This line of reasoning is ultimately unsustainable. That is, the fact that inherence and perception each constitute a sufficient explanation does not imply that they must compete in explaining the existence of a particular property-instance. To see why, let us consider an under-explored metaphysical phenomenon: ontological over-determination. 12 To be clear, I am not suggesting that Berkeley himself would have been sympathetic to this possibility. Berkeley ruled out the existence of material substances altogether and would therefore have rejected the possibility of inherence in matter. Mind-Dependence in Berkeley 11 There has, in the recent literature on grounding, been some discussion of cases of over-determined grounding (see, for example, Rosen [2010]). A disjunctive fact, for instance, can be grounded in either of its disjuncts; but, in a case in which both disjuncts are true, a disjunctive fact is equally grounded in each of its disjuncts. If, for example, Feldman is both a doctor and a lawyer, then the disjunctive fact that he is either a doctor or a lawyer obtains in virtue of each disjunct: if Feldman were not a lawyer, the disjunctive fact would still be grounded in the fact that he was a doctor, and vice-versa.13 Grounding is a sufficiency notion – a fact that has two full grounds has two individually sufficient conditions on its obtaining. If both grounds obtain, the fact is over-determined. If, on the other hand, we ask what the truth of the disjunctive fact depends on, there is nothing to privilege either disjunct. The fact that Feldman is either a doctor or a lawyer does not depend on the fact that he is a doctor – the disjunctive fact would have obtained even if it turned out to be false that he was a doctor, and vice-versa. So, in a case in which both of its disjuncts are true, a disjunctive fact depends on a disjunction, but on neither disjunct in particular.14 We can now ask what a case of ontological over-determination involving properties and substances looks like. Consider a single instance of yellowness. For this instance to be overdetermined, it has to be capable of bearing ontological relations to two distinct substances, where each could provide, in the absence of the other, full support for the instance. We have seen that there are indeed two distinct ontological relations an instance can stand in to a substance-inherence and perception-each of which provides full support. A case of ontological over-determination, then, involves both substances simultaneously doing their part: the over-determined instance simultaneously inheres in a substance and is perceived by a mind. As with the truth of a disjunctive fact, the existence of an over-determined instance does not depend on either of the two conditions in particular. It does not depend on the substance it inheres in because, even if it were not to inhere in that substance, its existence would nonetheless be guaranteed by the mind that was perceiving it. Similarly, it does not depend on the perceiver's mind – if the perceiver had closed her eyes, the very same instance would continue to exist just in virtue of inhering in its bearer. It must, nevertheless, depend on the substances in some way – we have been assuming that instances, by their nature, cannot enjoy an independent existence and need a substance to support them. So we should conclude that an over-determined instance's existence depends on a 13 Rosen cites this example as a 'harmless form of metaphysical over-determination'. 14 Cf. Audi [2012] and McSweeney [2020] for skepticism about disjunctive grounding. Mind-Dependence in Berkeley 12 disjunction – it depends on either inhering in the physical object or being perceived by the mind, but on neither disjunct in particular. Crucially, for such over-determined accidents to be possible, it has to be possible for both conditions to simultaneously obtain. This is where the importance of the distinction between inherence and perception-and thus the true significance of Berkeley's insight-comes into view. If sensible instances were supported by the mind in the very same way that they are supported by material substances-namely, by inhering in them-over-determination simply would not be possible. For inherence in one substance rules out simultaneous inherence in a distinct substance. The particular redness that inheres in the tomato in my shopping cart cannot, for example, simultaneously inhere in the tomato in my refrigerator. The particular desire that inheres in my mind cannot simultaneously inhere in your mind. The two tomatoes can, of course, bear instances of the very same kind- redness-but they cannot share the very same, single instance of that kind. Similarly, you and I can have exactly the same kind of desire-to hug an old friend, say-but we cannot share the very same instance of that desire. So, if inherence were the only notion of support at our disposal, there would be no room for one and the same instance to be simultaneously determined by a material body and a mind – there would be no possibility of over-determined instances. But, once we recognize that inherence and perception constitute two distinct kinds of ontological support, there remains no obstacle to two substances supporting a single instance. No aspect of our notion of inherence rules out the possibility that an instance that inheres in a material body may also be the object of a perceiver's awareness. For a material object serving as the bearer of a quality simply does not pose a threat to a mind's ability to perceive that quality. Similarly, the fact that a mind perceives an instance of a quality does not rule out the possibility of that very instance inhering in a distinct material object. For so long as the mind's role is not to serve as the bearer of the sensible quality, there is room for a material object to play that role. Thus, it turns out that the possibility of over-determined sensible instances hinges on our having expanded our ontological toolbox to incorporate the Berkeleian conception of perception. It is only once we recognize that the mind secures the existence of an instance of a sensible quality by perceiving it, and not by bearing it, that we carve out the logical space required for over-determination. What is the value of this discovery, though? One might conclude that over-determined instances are metaphysical mongrels that are logically possible but never actually encountered in the world, so no real benefit comes from acknowledging their possibility. In what follows, I will show how this Mind-Dependence in Berkeley 13 possibility is, in fact, of great significance: it is the key to a novel solution to a problem that bedevils all extant philosophical accounts of the mind – the age-old 'problem of perception'. §3.2. The Problem of Perception Two simple observations immediately generate the 'problem of perception'. First, ordinary perception is a matter of being aware of parts of the mind-independent world. More specifically, what it is like to have such a perception (its phenomenal character) seems to just be a matter of what the mindindependent objects themselves are like. Second, it is also possible to have strange experiences like hallucinations, which are identical to our ordinary perceptions with respect to their phenomenal character, but which do not involve awareness of any mind-independent objects whatsoever. The 'problem' is how to reconcile these two observations – if an experience with the very same phenomenal character can be had in the absence of any mind-independent objects, then surely these objects can play no role in fixing this character, even in the case of ordinary perceptions (even if they sometimes play a causal role in bringing about these perceptions). In one form or another, most philosophers of perception accept this line of reasoning. In what follows, I will argue that the reasoning is flawed and that the two observations are, in fact, perfectly compatible with each other. Let's consider the problem from within the framework we have developed so far. Consider a hallucinatory experience of a yellow banana. Just as in the case of a phosphene, the most plausible description of what it is like to enjoy such an experience makes reference to an actual instance of yellowness that the perceiver is aware of. As I have already suggested, we can employ Berkeley's notion of perception to explain how this can be true of a hallucination, despite the absence of any material or mental bearers of yellowness: in such an experience, the perceiver is aware of an actual instance of yellowness whose existence is guaranteed by the perceiver's state of awareness. Now, given that this instance exists only because of the perceiver's hallucinatory state, the instance is mind-dependent: it depends on the perceiver's mind. Acknowledging that hallucinated quality-instances are mind-dependent does not immediately taint the mind-independence of the yellowness of an ordinary banana. Without further argumentation, positing the existence of some mind-dependent instances of a sensible quality does not entail that all instances of that quality are mind-dependent. On the commonsense view, bananas are and remain yellow independent of anyone perceiving them to be any way. The fact that sometimes yellowness can be instantiated in the absence of any material bearers is perfectly compatible with this commonsense view. Sensible qualities like color and shape can be construed as qualities that straddle the ontological Mind-Dependence in Berkeley 14 divide – they can be instantiated either in virtue of inhering in a material object or in virtue of being perceived by a conscious mind.15 Unfortunately, though, our account of the hallucination does seem to threaten the view that in ordinary perception, we perceive the actual yellowness of the physical banana. For let us focus on a specific kind of hallucination, the kind that is brought about by replicating the neural state that the perceiver is in when she enjoys an ordinary, veridical perception of a banana. On the picture of hallucination just sketched, a hallucinatory experience involves the subject being aware of actual instances of sensible qualities. But if we can induce a hallucination just through direct neural stimulation, that means that intervening on the subject's brain can bring about actual instances of sensible qualities for the subject to be aware of. How is this possible? If the objects of awareness were ontologically independent of the perceiver's brain, intervening on the latter could have no effect on the existence of the former. The only way to allow for such hallucinations, then, is to concede that the state of awareness induced in the subject through direct neural intervention is sufficient, by itself, to secure the existence of a particular instance of yellowness. But now we come to the problem. The hallucination we are considering 'causally matches' an ordinary perception. (This locution comes from Martin [2004]. Also see Robinson [1994] for discussion of such cases). That is, the neural state that causes the perceiver's hallucination is identical, in kind, to the neural state that causes her veridical perception. If being in that kind of neural state was sufficient, by itself, to secure the existence of an instance of a sensible quality in the hallucination, it must have the same effect in the veridical perception too. That is, in the veridical perception, the perceiver's state of awareness must also be sufficient to secure the existence of an instance of yellowness. So we must concede that in all experiences, veridical and delusive, the perceiver's state of awareness guarantees the existence of sensible items of awareness. This is the conclusion that seems to threaten the possibility of perceiving the ordinary mind-independent world. For if all we ever perceive are items whose existence is guaranteed by our awareness of them, doesn't that mean we only ever perceive mind-dependent instances of sensible qualities? If this is a genuine implication of the 15 One might wonder how two instances whose existence is secured in such different ways could nonetheless count as instances of a single property, yellowness. In Sethi [forthcoming], I argue that a view of sensible qualities on which they have 'ontologically flexible' natures best accords with our pre-theoretical conception of these qualities. While such ontological flexibility rules out views on which colors are spectral reflectance patterns or dispositions, it is compatible with the kind of 'simple' or primitivist view of colors developed by Campbell [1997] and Allen [2016]. Mind-Dependence in Berkeley 15 picture being sketched, then even if bananas exist and are yellow independent of our perception of them, we never actually perceive their yellowness – the instances of yellowness generated by our own minds are forever 'getting in the way'. This would be an unattractive position to end up in, for it would force us to deny that perception, even in the best of circumstances, directly acquaints us with constituents of the mind-independent world. (See McDowell [1982] and Stroud [2009] for a discussion of the epistemological consequences of such a view.) This is in fact the position that sense-datum theorists end up in, once they insist that all perceptions make us aware of mind-dependent sense-data. It is precisely in order to avoid this implication that recent theorists of perception have overwhelmingly rejected the idea that we are ever aware of mind-dependent qualities, even in cases of hallucination. The threat that the possibility of hallucination poses to a naïve account of experience has come to be called the problem of perception. It lies at the heart of most contemporary views of perception. It has led some philosophers-the representationalists and qualia theorists-to conclude that the character of experience should never be described in terms of the items the perceiver is aware of. Other philosophers-the disjunctivists-instead reject the extremely plausible claim that hallucinations have the same phenomenology as ordinary perceptions. (See Hinton [1967]; Snowdon [1980]; Martin [2004] and Soteriou [2013]) None of these options is entirely satisfactory, as each requires us to deny some deeply intuitive claims, and so the philosophy of perception has remained at an impasse. (See Sethi [2020] for a more detailed discussion of the argument from hallucination and alternative responses to the argument.) Armed with a clearer understanding of the notion of mind-dependence, however, we can undermine the threat that leads to the problem. Given our account of hallucination, we must accept that a perceiver's state, even in a veridical perception of a yellow banana, is sufficient to explain the existence of a particular instance of yellowness. This is indeed common to the hallucination and the veridical perception. But this concession does not straightforwardly entail that the instance of yellowness that we are aware of in a veridical perception is mind-dependent. For we now know that it is possible for one and the same instance of a sensible quality to be over-determined. In such a case, the existence of the instance depends on a disjunction: it depends on either being perceived by a conscious mind or inhering in a material body, but on neither disjunct in particular. This is the key difference between the hallucination and the veridical perception. The instances of yellowness present in a hallucination have no form of substantial support aside from the perceiver's awareness of them. Given that their only way to exist is by being perceived, they depend on the mind Mind-Dependence in Berkeley 16 that perceives them. In a veridical perception, on the other hand, not only is the same kind of perceptual state present, there is also, crucially, a physical object present that is itself yellow. The physical object itself guarantees the existence of the instance of yellowness by serving as the bearer of the instance. Thus, the instance of yellowness present in a veridical perception is over-determined. While it is true that the subject's state of awareness is sufficient for the instance, given the presence of a second sufficient condition, the instance does not depend on the mind that perceives it. To the contrary, since the instance can outlive the perceiver's awareness of it-as long as the relevant material body exists for it to inhere in, an over-determined instance continues to exist beyond the perceiver's experience-it is robustly mind-independent. Cases of hallucination reveal that the mind's act of awareness suffices for the existence of its objects, even in cases of veridical perception. It has been universally-but falsely-assumed that, once this is acknowledged, we must conclude that the instance in question is mind-dependent. But as the logical possibility of over-determination reveals, x being sufficient for y does not entail that y must be dependent on x. So why has this move from the mind's sufficiency to mind-dependence seemed so natural? I want to suggest that an implicit commitment to the traditional framework of inherence can help diagnose this error. If the only way a substance can guarantee the existence of a quality-instance is by the instance in question inhering in that substance, then the possibility of hallucinations poses a very real threat to our account of ordinary perception. For if hallucinations reveal that the mind can support the existence of sensible instances, then given the traditional framework, this must mean that these instances inhere in the mind. And, if the perceiver is in the very same internal state in the hallucination and the veridical perception, then in the veridical perception, too, the perceiver must be aware of items that inhere in the mind. Once we have conceded this, we really have ruled out the possibility that we could be aware of the qualities of an ordinary physical object. For if the qualities we perceive inhere in the mind, they cannot also inhere in a worldly object. But this reasoning only goes through on the assumption that the relationship between a mind and the qualities whose existence it guarantees must be inherence. We have, in our discussion of Berkeley, rejected this assumption. By doing so, we have opened up the possibility that one and the same instance could have its existence guaranteed by the mind-in virtue of the mind perceiving it-and nonetheless inhere in a material object. Introducing the possibility of ontological over-determination provides a compellingly unified account of sense perception. We can do justice to the rich phenomenology of delusive perceptions- experiences of phosphenes, after-images and hallucination-by insisting that such experiences make Mind-Dependence in Berkeley 17 us aware of actual (although mind-dependent) instances of sensible qualities. Here, we make heavy use of the notion of perception I have traced back to Berkeley. Departing from Berkeley, we can develop this account of delusive perceptions without relinquishing the view that ordinary perception puts us into direct contact with the mind-independent world. For the instances we ordinarily perceive are the very same instances that inhere in material objects (the objects whose existence Berkeley denied), and these instances continue to exist in those material objects beyond our perception of them. Finally, given that both veridical and hallucinatory experiences acquaint us with instances of the very same kinds of sensible qualities-color, smell, taste, shape and size-we can also accommodate the intuitively plausible thesis that hallucinations and ordinary perceptions can share phenomenal character. For whether the instances of color, shape, smell and size are mind-dependent or mindindependent does not affect the phenomenology of our experiences. What determines our phenomenology is which kinds of qualities are instantiated, not the ontological status of the particular instances.16 §4. The Nature of Sensible Instances §4.1. Publicity The key insight I have defended so far is that when I perceive a yellow banana, even though my state of awareness guarantees the existence of the yellowness that I perceive, that very yellowness can also inhere in the banana itself. In this section, I briefly want to discuss whether my account is compatible with the public nature of sensible qualities – that is, with the fact that you and I can perceive the very same yellowness that the banana possesses even when no one is looking. For it is surely a central desideratum that our view make sense of such facts. The question about public perceivability relates to a more general question about the view. I have claimed that the yellowness of a banana has its existence guaranteed by the banana that it inheres in. When it is unperceived, there is no other condition in place that secures its existence, and so the yellowness depends on the banana for its existence. When it is perceived, on the other hand, there are two conditions that guarantee the instance's existence-inherence in the banana and perception by a mind-and so the instance in question is over-determined. 16 The view is a version of naïve realism that rejects disjunctivism. Like naïve realism, it claims that veridical perception puts us in direct contact with mind-independent objects. Unlike disjunctivism, it treats hallucinations and veridical perceptions as phenomenologically identical. Mind-Dependence in Berkeley 18 The general concern is that of whether this change in what the instance depends on counts as a change in the nature of the instance. It is a key part of the framework within which I have been operating that the dependence of accidents on substances issues from the very nature of the accidents themselves. And so, if the conditions on an accident's existence change over time, it would seem that its nature changes over time. But how, then, could it be the very same yellowness that is first unperceived, then perceived? It seems we are forced to relinquish the idea that we perceive the very same quality-instances that exist independent of our minds, when we are not perceiving them. Alternatively, we might suggest that it is true all along that a given instance's nature involves a reference to the particular mind that (eventually) perceives it. But this seems equally implausible. For the coming into or going out of existence of some perceiver should not make a difference to the nature of a banana's yellowness. Furthermore, if the nature of the instance in question implicates one perceiver, in order to make room for the joint perceivability of such an instance by multiple perceivers, it will have to implicate each potential perceiver in one giant disjunction. We seem to find ourselves in a dilemma. Fortunately, we are not forced into either of these positions. In response to the first horn of the alleged dilemma: The banana's yellowness undergoes no essential change upon being perceived. What we should take away from the observation that yellowness can be instantiated in one of two ways, is that all instances of yellowness-in so far as they are instances of yellowness-have a nature that places disjunctive conditions on their existence. So even when the banana is unperceived, it is part of the nature of the instance of yellowness that its existence can be guaranteed either in virtue of inhering in the banana or in virtue of being perceived by a mind. When a perceiver walks into the room and looks at the banana, there is no change in the nature of the instance. Rather, what changes is that now both conditions on its existence obtain, whereas prior to the act of perception, only one did. In response to the second horn: this strategy does not require that we build particular perceivers into the nature of mind-independent instances. Perceived or unperceived, it is part of the nature of the banana's yellowness that its existence depends either on inhering in the banana or being perceived by someone. When I perceive the banana, the latter disjunct is made true by my act of perception. When my mother perceives the banana, the same disjunct is made true by her act of perception. When both of us perceive the banana, it is made true by each of us. But the nature of the instance remains unchanged and does not specify any particular perceiver. This discussion highlights two important lessons. First, what an instance depends on in virtue of its nature can come apart from what an instance in fact depends on at some point in time. By its nature, Mind-Dependence in Berkeley 19 an instance may depend on a disjunction; that is, it may depend on either inhering in some material object or being perceived by a conscious mind. Take our banana's yellowness. By its nature, this instance depends either on inhering in the banana or being perceived by a mind. When the banana is unperceived, only one of these conditions obtains and so the yellowness in question depends for its existence on the banana. But it does not depend on the banana in virtue of its nature.17 For even when no one is perceiving the instance, its nature still places disjunctive conditions on its existence. When someone walks into the room and perceives the instance, its existence comes to be over-determined (and thereby ceases to depend on the material object it still inheres in). But through these changes in what actually secures its existence, and what, therefore, it actually depends on, its nature remains unchanged. If the banana's instance can have its existence supported by multiple perceivers, why can't it also have its existence supported by multiple material objects? Why is there an asymmetry in the level of specificity in the two disjuncts? This question leads to the second lesson: instances are individuals. The nature of one instance must, therefore, differ from the nature of a distinct instance of the same kind. Take all of the instances of yellowness. These instances must share that aspect of their nature that makes them all instances of yellowness (as opposed to instances of redness, say). But this cannot be their entire nature. Because in so far as they are instances (as opposed to kinds), this banana's yellowness must essentially differ from that banana's yellowness. The traditional hierarchy between substances and accidents, accepted both by inherence theorists and by Berkeley, treats accidents as ontologically dependent on substances precisely because these instances are individuated by the substances that secure their existence. This banana's yellowness is distinct from that banana's yellowness in virtue of the two bananas themselves being distinct individuals. We can maintain the individuative role that substances play even within our framework. This is where the asymmetry of the two disjuncts becomes relevant. Consider, for instance, the class of sensible instances that inhere in ordinary material objects – the mind-independent instances. The nature of each instance in this class references perception by a mind without specifying any particular mind. With respect to this aspect of its nature, a mind-independent instance does not differ from any other mind-independent instance – the public perceivability of such instances means that none of them are linked to any specific subject. The other disjunct, however, does specify a unique condition. A particular instance of yellowness can be perceived by multiple minds, but it cannot inhere in any 17 Using our Finean terminology, the unperceived instance depends on the banana, but it does not dependINH on it. Similarly, a hallucinated instance depends on the mind that perceives it, but it does not dependPER on it. Mind-Dependence in Berkeley 20 number of material objects: this banana's yellowness is essentially this banana's yellowness. Its nature is essentially tied to this particular banana and this is what distinguishes it from all other instances of yellowness.18 There is, therefore, one important difference between mind-independent instances and minddependent instances of a sensible quality. In so far as the banana's yellowness and the phosphene's yellowness are both instances of yellowness, they are both instances that can be instantiated in one of two ways. That being said, mind-independent instances are individuated by their material disjuncts while mind-dependent instances are individuated by their mental disjuncts. Just as this banana's yellowness cannot be numerically identical to a second banana's yellowness, the yellowness that I hallucinate cannot be numerically identical to the yellowness that you hallucinate. §4.2. Fission and Fusion So far, I have suggested that the presence of a material body in a veridical perception makes a perceived instance over-determined. But this claim needs refining. For the mere presence of a mind-independent object does not guarantee that the instance a subject perceives is over-determined. To see this, it will be helpful to contrast veridical perception with veridical hallucination. In a veridical perception, a mind-independent object is present, and a perceiver is aware of it. In a veridical hallucination, a mindindependent object is also present, but the perceiver is not aware of it. Rather, she is undergoing a hallucination that happens to correspond to the way the world is. In his classic discussion, Grice [1961] uses such cases to show that a mere correspondence between perceptual experience and the world does not entail that one is perceiving the world: genuine perception of an object requires that the object cause the perception. (Also see Strawson [1974] and Pears [1976]). Grice's basic insight is that what a subject is aware of depends on what plays a causal role in generating her perception. For us, the question of what a subject is perceptually aware of is a question of which quality-instances her perception supports. So, Grice's insight can be translated as follows: which quality-instances a perceiver's state supports depends on what plays a causal role in generating that perceptual state. What is required, then, for a subject to perceive the banana's yellowness is that her state of awareness be causally hooked up to the banana in the right way. What makes it possible, 18 One could develop a more radical metaphysics on which individual instances have natures that are wholly identical with respect to the conditions on their existence. On this approach, instances could be individuated in some other way and one and the same instance could maintain its identity across a variety of bearers. This is not a strategy I pursue here. Mind-Dependence in Berkeley 21 in a genuine case of perception, for a perceiver's state of awareness to sustain the very same instance that inheres in the material object is the existence of a causal link between the material object and her state. In a veridical hallucination, in contrast, the instance that a mind supports cannot be the instance that inheres in the banana because there is no causal connection between the mind and the banana. Imagine that Aleeya is veridically perceiving a yellow banana. According to our picture, Aleeya is aware of an over-determined instance of yellowness. Now, unbeknownst to her, a neuroscientist removes the banana but directly stimulates Aleeya's brain so that she begins to enjoy an indistinguishable hallucination of a yellow banana. I have just suggested that a state of awareness can only latch onto the instance that inheres in a mind-independent object if that state of awareness is causally sustained by the mind-independent object. This condition, while satisfied during the initial veridical perception of the banana, fails to hold once the transition occurs. But what becomes of the over-determined instance that Aleeya was perceiving a moment ago? So far, I have indicated that when an object ceases to be perceived, the quality instance that was over-determined during the act of perception continues to exist, now unperceived, solely in virtue of inhering in the material object. But in this case, it might seem like both sustaining conditions – the material object and the perceiver's state – continue to exist, now independent of each other, after the transition. Why, then, doesn't the overdetermined instance remain with the perceiver, so to speak, as opposed to with the object? It seems like we have on our hands a case of fission – what was a single over-determined instance during the act of perception splits into two instances, one solely supported by the perceiver's state of awareness, the other solely supported by the material object, each of which has equal claim to being identical to the instance that was perceived a moment ago. The way out of this maze is already implicit in our discussion of the causal nature of perception. When the physical object is replaced by artificial neural stimulation, the connection between Aleeya's mind and the object is severed. And so, the particular state of awareness Aleeya was in-the one that was causally connected to the object and so could therefore sustain an awareness of the banana's yellowness-can itself no longer exist. The new state of awareness she is now in-a hallucinatory state that is entirely disconnected from the object-must, therefore, have a numerically distinct instance as its object. Hence, despite initial appearances, the second condition that sustained the over-determined instance during the veridical perception does not itself exist beyond the transition. What does persist is the material object, and so the only way for the formerly over-determined instance to continue to exist is by inhering in that object. The intuitive idea here is that a particular perceptual state is individuated partly by the causal process that gives rise to it. While two states of awareness-veridical Mind-Dependence in Berkeley 22 or hallucinatory-can be of exactly the same kind despite being caused in different ways, one and the same particular state cannot persist through this kind of change in causal ancestry.19 For the same reasons, a transition from a hallucination to a veridical perception will also involve different particular states of awareness and, therefore, different instances. That is, a hallucinated minddependent instance cannot be numerically identical to a perceived instance that inheres in a material object. The material instance could surely already have existed (perhaps in a different location) at the very same time as the subject was suffering her hallucination. If the instance that was being hallucinated could persist beyond the transition from hallucination to veridical perception, this would entail that two distinct instances that simultaneously existed a minute ago could now fuse into a single instance – a scenario that is just as suspect as the one involving fission. Individuating particular states of awareness by the causal processes that give rise to them rules out this possibility as well: when the subject transitions from a hallucinatory state to veridically perceiving the banana-when the cause of her mental state changes-she can no longer be in numerically the same state of awareness, and so the particular instance of yellowness her state sustains cannot be the same. One might worry that the view has become ad hoc. For it now seems like the only case in which the two forms of support can be implicated in the existence of a single instance is in a case of genuine perception. Relatedly, the only transition which sustains the existence of a single, over-determined instance is the transition from an unperceived instance to a perceived instance. But what I hope to have brought out in this section is that this consequence is far from ad hoc. I have suggested that a state of awareness can latch onto an instance out there in the material world-one that is already supported by a material object-only if that state of awareness is itself causally connected to the object in the right way. Without such contact between the material world and the mind, it would be entirely mysterious how the two substances could overlap in the explanation of one and the same propertyinstance. It is only in the case of genuine perception that such contact is secured.20 19 This is compatible with the state of awareness in the veridical perception being sufficient for the instance that inheres in the banana. Remember, we know through reflection on the hallucinatory case that 1) the very same kind of state can independently sustain an instance of yellowness and 2) the very same kind of instance can be fully supported by a perceiver's state of awareness alone. This is what motivates the view that the perceiver's state must be sufficient for the perceived instance. If, per impossibile, the particular state that obtains in the perception could continue to exist in the absence of a causal connection to the banana, then the very same instance that was veridically perceived could now be sustained by the perceiver's state of awareness alone. 20 The resulting over-determination has the following, interesting logical form: One sufficient condition (the perceiver's state of awareness) turns out to be dependent on the second sufficient condition (the banana). But this dependence between the two sufficient conditions does not invalidate the status of the instance as overdetermined. Consider our earlier example involving the disjunctive fact that Feldman is either a lawyer or a Mind-Dependence in Berkeley 23 §5. Conclusion Even after he has concluded that sensible qualities are nothing but ideas in the mind, Berkeley insists that it is sensible objects that are colored and shaped. He writes [Three Dialogues, 230]: A piece of sensible bread, for instance, would stay my stomach better than ten thousand times as much of that insensible, unintelligible real bread you [the materialist] speak of. It is likewise my opinion, that colors and other sensible qualities are on the objects. I cannot for my life help thinking that snow is white and fire hot. On the reading that I have put forth here, we have a novel way to grant Berkeley's desire to treat the snow and the fire themselves as the bearers of sensible qualities. For once we see that for a particular sensible accident to be 'in the mind' is just for the mind to secure the existence of the accident through an act of perception, the question as to what, if anything, is the bearer of that quality is left entirely open. As a result, it is compatible with the view that a particular heat exists because it is perceived by the mind that it nonetheless inheres in a physical object-the fire. Although Berkeley himself rejects the possibility that sensible qualities could inhere in material objects, there is nothing within his very notion of perception that rules out this possibility.21 Furthermore, I have argued that once we distinguish the ways in which material objects and minds secure the existence of qualities, we can see that mind and matter need not serve as competing explanations for those qualities. This lack of competition opens up the possibility of over-determined instances – instances whose existence is explained equally by the mind and by the material world. Recognizing this possibility, in turn, gives us the resources to develop a novel solution to the problem of perception. For once we recognize that an accident can be over-determined, we can concede that a perceiver's state is sufficient to secure the existence of an instance of a sensible quality, in both veridical and hallucinatory experiences, while insisting that the instance of the quality in the veridical perception is still robustly mind-independent. An instance that is over-determined will continue to exist in the absence of the perceiver's awareness; it will continue to exist in the physical object that is its bearer. doctor. Even if becoming a doctor somehow depended on being a lawyer, Feldman could still be both a doctor and a lawyer, and in such a case, the truth of the disjunctive fact would still be over-determined. 21 Berkeley's own strategy is to treat the snow and the fire as a bundle of property-instances and to predicate whiteness or heat of such a bundle. But this strategy denies the intuition that the snow is ontologically prior to its color, that it could be the very same snow despite being muddied. This denial is consistent with Berkeley's idealism, of course, but is not a strategy that we should endorse. Mind-Dependence in Berkeley 24 All this from the simple, but radical, idea that minds offer a unique kind of existential support to sensible qualities. If Michael Ayers [1970: 49] is right that the new 'Principle' about which Berkeley expresses so much excitement in the Notebooks is not his idealism, but rather the thesis that the mind supports sensible qualities by perceiving them, then, although Berkeley had himself only just glimpsed the true scope of his proposal, I hope to have shown that his excitement was well-justified indeed.22 Brandeis University References Ackrill, J. L. 1963. Aristotle: Categories and De Interpretatione, Oxford: Oxford University Press. Allaire, Edwin 1963. Berkeley's Idealism, Theoria 29/3: 229–44. 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