A STRAIGHTFORWARD SOLUTION TO BERKELEY’S PUZZLE

JOHN CAMPBELL

1. The Explanatory Role of Experience

Berkeley (1734) thought that we cannot but take the existence of a thing to be a matter of its being perceived: “The table I write on, I say, exists, that is, I see and feel it.” In general, he thought that we could not form the conception of an objective, mind-independent reality: “all the choir of heaven and furniture of the earth, in a word all those bodies that compose the mighty frame of the world, have not any subsistence without a mind … their being is to be perceived or known” (Berkeley 1734). The argument that seems to compel Berkeley to this conclusion is, I think, quite forceful. The problem it raises is how we can acknowledge its force while not being swept along to his conclusion. The argument that is really doing the work in Berkeley is an argument from the explanatory role of experience. There are two basic ideas in the argument:

(1) Our understanding of concepts of the medium-sized world is grounded in our sensory experience, and
(2) Sensory experience can provide only concepts relating to sensory experience itself.

More generally, we might say that what is driving Berkeley’s argument is the idea that perceptual consciousness has an epistemic role to play in our cognitive lives. That is, it is because we are conscious that we have knowledge of particular properties and objects. It is only because we are conscious that we so much as have the conception of the various characteristics and objects that are in our world. And it is only because we are conscious that we have perceptual knowledge of the facts about our world. But, Berkeley is arguing, the only epistemic role that experience can have is to provide us with knowledge of experience itself. Berkeley’s argument is troubling and forceful for us because each of these premises has a lot of plausibility. Certainly, each of these premises would find many supporters among contemporary philosophers. Suppose you simply ask what the point is of perceptual experience, what good it does us that we have sensory experience. The answer that immediately seems compelling is that it is because we have sensory experience that we know about the things around us and their characteristics. It is only because of our experience of ordinary objects and their properties that we so much as have the conception of those objects and properties. At the same time, suppose you ask, “How exactly can sensory experience provide us with knowledge of the things around us?” People very often think of consciousness as a matter of experience having a certain qualitative character; and how can that qualitative character of experience be a crucial element in our knowledge of anything other than that very type of experience itself? The qualitative experiences, the qualia that we find in our minds, do not provide us with insight into what the external world is like. There are no qualia in any non-mental, physical world. It is hard to see how consciousness as such can provide us with knowledge of anything but itself. So if we accept that it is our experience of ordinary objects that allows us to form the conception of those ordinary objects, we seem driven to the conclusion that we can form the conception only of objects that are themselves merely aspects of our experiences, objects that are themselves creatures of the mind. Berkeley’s Puzzle is to understand how it could be that both (a) our grasp of concepts of ordinary objects is grounded in our experience of those objects, and (b) we have the conception of mind-independent objects. To resolve this Puzzle, I will argue, we have to look again at our conception of sensory experience; we have to think of sensory experience not as a matter of having qualia, for example, but as a matter of our being related in the right kind of way to the objects and properties around us.

There are two radical resolutions of the Puzzle. One is to say that the conclusion is correct: that we have only the conception of experience itself, and no such idea as that of a mind-independent material object. This is Berkeley’s own solution, of course. The other radical resolution is to say that sensory experience plays no role in our understanding of the concepts of the things and properties around. This is the standpoint of contemporary epiphenomenalism about conscious experience.

In this essay I will try to set out a straightforward resolution of Berkeley’s Puzzle: that is, one that accepts both (a) that our grasp of concepts of ordinary objects is grounded in experience of those objects, and (b) that we have the conception of mind-independent objects. To set out the straightforward resolution of Berkeley’s Puzzle we have to look a lot more critically at the idea of our grasp of concepts of ordinary objects being ‘grounded in’ experience of those objects; and we have to look a lot more critically at the idea of a conception of objects as ‘mind-independent.’ The most important single idea we have to have in play, though, to give a straightforward resolution of the Puzzle, is the conception of sensory experience as a relation between the perceiver and the scene observed. On a Relational View of Experience, sensory experience is characterized as a three-place relation holding between:

(i) the observer,
(ii) the point of view from which the scene is observed, and
(iii) the scene observed.

This three-place relation is “x is experiencing y from point of view z”, and as we shall discuss, it may itself be adverbially modified. The key point about any such view is that the scene observed cannot be eliminated from a description of the sensory experience. To be having a perceptual experience is, characteristically, to be experiencing a particular scene from a particular point of view; characterizing the qualitative character of the experience involves characterizing the qualitative characters of the objects and properties in the scene observed. The qualitative character of the sensory experience is constituted by the qualitative characters of the objects and properties in the scene observed. These are, as I have said, not the only components to a characterization of the experience; we have also to describe the point of view from which the scene is observed, and comment on any adverbial modifications of the relation of experience.

With this conception of sensory experience in hand, it is possible to resolve Berkeley’s Puzzle straightforwardly: that is, to acknowledge both the explanatory role of experience in our conception of the things around us, and our grasp of concepts of mind-independent objects. We first need to say something more about what it means for sensory experience to have a role in explaining our grasp of the conception of objects as mind-independent. Then we need to say something about how sensory experience, conceived as on the relational view, could play this role.

2. Ways of Thinking That Reflect Objectivity

There are two dimensions to grasp of a term referring to an ordinary physical object. There is, first, one’s grasp of the characteristic patterns of inference to which the term is subject. There is, second, one’s grasp of the justification for the use of those patterns of inference in connection with the term. That grasp of the semantic justification for the pattern of use of the term is what provides the most basic role for perceptual experience in our grasp of concepts relating to the medium-sized world.
There are characteristic ways in which we think and reason about ordinary physical objects that reflect the mind-independence we usually take physical things to have. We can think of the mind-independence of ordinary concrete objects as showing up in three different ways:

(1) It is the same object that we encounter over time. The object continues in existence even when it is not being observed. Even when the object is observed continuously over a period of time, there may be changes in the observation of it that do not reflect any change in the object, or any change of the object.

(2) It is the same object we encounter in different sensory modalities. You can see and touch one and the same thing, stick it in your mouth, and so on. There is one and the same thing here, through variation in the way it is being experienced by you.

(3) Different people can encounter one and the same object. The subjective experiences they have of the object are different to one another, but it is one and the same thing. So here there is variation both in who is having the experience and in what kind of experience it is, consistently with it being one concrete thing that is experienced.

It is fairly easy to see that Berkeley conceives of objects as mind-dependent. On his view, the identity of an object just is the identity of a perception, and two people cannot share the same perception, just as the same perception cannot be encountered in different sense-modalities or at different times. Yet obviously we do ordinarily talk in terms of one and the same object being encountered by different people, through different sense-modalities and at different times. How is it that we have the conception of it being one and the same object here? How is it that we can conceive of the unity of an object without conceiving of it in terms of its relation to a mind? The suggestion that has been most considered by theorists working on the subject is that our conception of the unity of an ordinary concrete object is the conception of a causal unity. To have the conception of concrete objects as mind-independent is to have some understanding of their identity-conditions; and those identity-conditions have to do with the causal dependence of the way the object is later on the way the object was earlier. When we characterize the identity of the object in this way, we do not need to bring in its relation to a mind. That is how we have the conception of the object as mind-independent.

When I put it like this, however, it may look as though we could give a comprehensive characterization of how one has the conception of objects as mind-independent without bringing in one’s experience of objects at all. For you could give a theoretical characterization of the causal dependencies here, and how the subject grasps them, without mentioning the subject’s experience of objects. So this way of explaining what it is to have the conception of objects as mind-independent may seem to lose any role for the subject’s experience of objects. All our understanding of objects as causal unities could be, as it were, theoretical, rather than being grounded in sensory experience.

To see just where experience comes in, notice that in general, we think of causal connections in two ways. First, we think in terms of causation as a matter of there being a counterfactual connection between two variables, Y and X. For Y to be counterfactually dependent on X is for it to be the case that the value of Y would have been different, had the value of X been different. The kinds of variables that matter for questions of the identity of objects are variables such as “whether saw Y cut through the wood easily at t2”, and “whether saw X had been oiled at t1”, where t2 is later than t1. If saw Y and saw X are different saws, then there will in general be no counterfactual dependence of the first variable on the second. That is, how easily saw Y is cutting through the wood would not have been any different whether or not you had oiled saw X. However, if the value of variables such as that first variable is counterfactually dependent on the value of the second variable, then that is the kind of causal connection that it takes for saw Y at t2 to be identical to saw X at t1. A grasp of this kind of counterfactual connection between variables relating to how the object is later and variables relating to how the object was earlier does not seem to exploit the subject’s experience of the object. (Of course, it is a familiar point that the counterfactuals here must not be “backtracking” counterfactuals. But I will not pursue that issue here.)

There is a second dimension to our ordinary thinking about causation. We do not think merely in terms of counterfactual connections between variables; we think in terms of mechanisms by means of which the counterfactual connections exist. Suppose we consider any finding established by a randomized controlled trial, such as a role for vitamin E in the prevention of heart disease. The trial might establish that interventions on the level of vitamin E in a patient will make a difference to the risk of heart disease. But there is a further, compelling question: What is the mechanism by which vitamin E affects the risk of heart disease? The answer: “There is no mechanism” would seem barely intelligible to most researchers. The truth of the counterfactuals is one thing, and the mechanism implicated in the causation here is something else. The notion of a mechanism here is notoriously difficult to characterize, and I am not going to attempt a general characterization of it, beyond remarking on its importance. For us the key point is that a prototypical case of a mechanism is provided by our ordinary conception of an ordinary medium sized object transmitting causal influence from place to place. This is one of the prototypical examples of a mechanism, and it provides us with one of the basic pictures of what a mechanism is that we bring to more difficult cases.

Let me give a simple example. Suppose I have two knives, knife A and knife B., and I have a knife-sharpener. Knife B is over at the cutting-board, with tomatoes ready to be chopped. Knife A is at the other end of the room, beside the knife-sharpener. Here are two cases:

Case 1. I sharpen knife A, and put it down beside the sharpener. I go to the other side of the room and use knife B to chop tomatoes. The chopping goes faster and better than it would have done if I had not sharpened knife A. Let us suppose that this is established by extensive experiment.

Case 2. I sharpen knife A. I take it over to the chopping board and use it to chop tomatoes. The chopping goes faster and better than it would have done if I had not sharpened the knife.

Case 1 is an unusual and puzzling case. How does it happen that the intervention at the sharpener is making a difference to what happens over at the cutting board? The natural question is, “What is the mechanism?”. Surely this must be some kind of conjuring trick. There must be some kind of machinery linking the two places, at the sharpener and at the cutting board, that we haven’t yet described. Case 2 seems quite different. What has happened at the sharpener is making a difference to what happens at the cutting board. But there is no puzzle about how this is happening. It is not that there is no mechanism here for transmitting causal influence from place to place. There is a mechanism. It is the movement of knife A. The movement of knife A from one place to another is the mechanism by which causal influence has been transmitted from one place to the other. This point is evidently quite general. The movements of concrete objects from place to place are the mechanisms by which causal influence is transmitted from place to place. This point is so familiar that it is easy to miss. But once you point it out, it is obviously basic to our thinking about causation in the immediate environment. That is what I mean by saying that concrete objects here are prototypical mechanisms by which causal influence is transmitted.

You might say that this is just a matter of what we are familiar with as opposed to what we are not familiar with. We are not familiar with Case 1 interventions whereas we are familiar with Case 2 interventions. But that response understates the contrast. Suppose Case 1 interventions did become commonplace. We would still look for a mechanism explaining why they happened. Similarly. we look for mechanisms explaining why light switches turn on lights, no matter how familiar we are with the phenomenon. It is not that there is some a priori guarantee that we will always find what we are looking for. It is just there is some looking to be done. In a Case 2 intervention, however, it is not just that the thing is familiar. The mechanism linking intervention and upshot is palpably there. Ordinary perception confronts us with the mechanism.
One reason it is easy to miss this point is that when we are looking for mechanisms we are often looking for something hidden. For example, it might take a lot of work to find the mechanism linking vitamin E with heart disease. But in this case the mechanism in play is perfectly obvious. You might point out that there is a hidden structure here, the molecular composition of the knife being transported from place to place. But this is not an alternative to thinking of the movement of the knife itself as the mechanism for the transmission of influence. All it provides us with is an equation: the movement of the knife is the movement of a collection of molecules. That identity may be true, but it is still the movement of the knife from place to place that is the mechanism for the transmission of causal influence.

To put this all together. A grasp of the identity of knife A over time may consist partly in a grasp of counterfactuals saying that what happened with the thing later would not have happened without what happened with the thing earlier. You know that an intervention on A earlier will make a difference to how it is later. But a grasp of the identity of A provides more than this. Your grasp of the identity of A means that you know the mechanism linking what happens at the earlier place to what happens at the later place. In contrast, you could know that an intervention on A is going to make a difference to how B is later. But you might still not know the mechanism involved. Knowledge of the mechanism involved is something over and above knowledge of the counterfactual. This understanding of the physical object as mechanism is not a matter merely of knowing, explicitly or implicitly, various counterfactuals about what would happen under interventions. In the absence of experience of objects, it is difficult to see how we could have such a conception at all. It is our sensory confrontation with the categorical object itself that provides us with our grasp of that which makes the counterfactuals true.
Suppose we do have this conception of physical objects as the prototypical mechanisms for transmitting causal influence from place to place. This is a conception of the concrete object as mind-independent: you think of the mechanism as having a unity that has nothing to do with its relation to any mind. A grasp of this idea cannot be explained as a matter of, for example, understanding in practice that your actions on the object earlier will make a difference to how it is later. You could grasp that there was this fact about the upshot of your actions without having any idea what mechanisms are involved. Our ordinary conception of a concrete physical object does provide us with an understanding of a mechanism, which must go beyond a mere practical grasp of intervention counterfactuals. So in virtue of what do we have this conception of the object as a mind-independent unity? The great merit of the Relational View of Experience is that it lets us understand how experience of the object could provide us with this conception.

3. The Relational View of Experience

We reason in ways that reflect our conception of objects as mind-independent. We engage in reasoning to establish object-identity that proceeds by arguing that the later object is the way it is only because the earlier object was the way it was; therefore, they are identical. Suppose, for example, that you visit your old schoolroom and find your initials still carved on a desk. You have the right to take it that it is the same desk; the initials would not be there now if it was not for your industry all those years ago. More fundamentally, we take ourselves to have a conception of “the desk itself,” on which the concrete object functions as the mechanism by which the influence of your earlier work is transmitted over time to the present. These ways of thinking reflect a conception of the object as mind-independent. Our question is whether we have any justification for reasoning in this way, and in particular, whether perceptual experience could provide us with any justification for reasoning in this way. Berkeley’s argument was that perceptual experience provides us with no such justification. Since it is only perceptual experience that can justify our use of particular patterns of reasoning about our surroundings, it follows that these patterns of reasoning are not legitimate and should be abandoned.
An alternative reaction, as I have said, is provided by contemporary epiphenomenalism, according to which perceptual experience plays no role in our knowledge of our surroundings, that is, no role in our grasp of concepts of the objects and properties around us. Someone who holds this view may say that there is no justification to be given of those ordinary ways of reasoning. This is just the way of our people, to talk and think in terms of mind-independent objects. Here we reach bedrock and the spade is turned.
Neither of these reactions seems particularly compelling. On the one hand, it is hard to believe that perceptual experience licenses us only in thinking and reasoning in terms of objects that are mind-dependent: transient, modality-specific, and perceiver-specific. The view that we can think only in terms of mind-dependent objects is simply impossible to believe, when ordinary perceptual experience seems to provide us at every moment with crowds of mind-independent things. On the other hand, the idea that we actually have no justification for thinking in this way—the idea that perceptual experience cannot underwrite these styles of reasoning—is equally hard to believe. These patterns of reasoning are not simply plucked out of the air, or imposed by us on a malleable reality—perceptual experience confronts us with the very mind-independent things whose being there validates these patterns of inference. That is what makes Berkeley’s Puzzle inescapable. We have to explain how it can be that sensory experience can be validating our reasoning about mind-independent material things.

In particular, let us focus on our ordinary conception of material objects as the mechanisms by which causal influence is transmitted from place to place and time to time. If we think of perceptual experience as a relation between the perceiver and the ordinary, mind-independent objects in the environment, then we can immediately see how perceptual experience could play a role in our having this conception. The key point is this:

On the relational view, the qualitative character of the experience is the qualitative character of the object itself.

As I brought out earlier, and I will return to the point in a moment, there is more to be said than this about the qualitative character of experience, on a relational view. There is the point of view from which the scene is being observed, and there may be adverbial modification of the type of experience in question. But the key point is that once these other parameters are set, on the relational view, the qualitative character of the experience is then constituted by the qualitative character of the object. That is what is distinctive of the relational view of experience.

It is because of this that the relational view of experience can explain how it is that we have the conception of the categorical concrete object as the underlying mechanism by which causal influence is transmitted. The concrete object, such as the knife we discussed earlier, is not a hypothesized cause; it is not known merely as a locus of counterfactual causal connections. Sensory experience brings the thing itself into view, the categorical basis of the counterfactual connections. Consider, in contrast, analyses of perceptual experience on which there is a distinction to be drawn between the qualitative character of the experience and the qualitative character of the object. That means that, on these analyses the experience itself does not bring the qualitative character of the object into the subjective life of the perceiver. The qualitative character of the experience is at best an effect of the qualitative character of the object perceived, on these analyses. So these analyses cannot explain how it is that a sensory encounter with the object can be an element in one’s grasp of the idea of the object as the categorical basis for the counterfactual connections between the way the thing is at one time and place and the way the thing is at another time and place.

The relational view of experience can similarly justify the patterns of inference that reflect our conception of objects as mind-independent. Suppose, for instance, that you consider some exercise of reasoning that uses the conception of sameness of object over time. Then, I am suggesting, what validates the correctness of the use of that pattern of reasoning is that the object is identified by your experience of it; and your experience of it is experience of a mind-independent object that is indeed the same over time, despite variation in other aspects of your sensory experience of it, or through gaps in your sensory experience of it. Similarly, in the cross-modal case, what justifies you in using a pattern of reasoning that uses the conception of sameness of object across sensory modality is the fact that your perceptual experiences in different sensory modalities have related you to one and the same object. And in the interpersonal case, what justifies you in reasoning in a way that exploits the sameness of the object that you and the other person have encountered is that you have both been experientially related to one and the same object. Of course, it can happen that you think you have justification for using a particular pattern of inference when you do not. Despite it seeming for all the world as though you have encountered the same object as one time as at another, there may in fact have been a switch. You can take yourself to seeing and feeling the same object when actually the thing you are seeing is not the same as the thing you are feeling. You can take yourself to be encountering the same object as someone else is encountering when in fact you are related to different things. In such cases your perceptual experience is not what you take it to be. Your perceptual experience does not validate the patterns of inference that you suppose it to. Moreover, even in the cases in which it is in fact the same object that is being encountered, across times or modalities or persons, that mere sameness of object is not enough for perceptual experience to validate the correctness of inferences that exploit the sameness of the object. As we saw already, in setting out the relational view of experience, it would not be right to think of perceptual experience as merely a two-place relation between the perceiver and an object. You experience scenes from a particular point of view, and there may be adverbial modifications of the relation of experience. So we have to say that for one’s perceptual experiences to justify the use of patterns of inference that exploit the sameness of the object, it must be not just that those experiences do in fact relate one to a single object, they all have to relate one to that object in suitably related ways.

Our understanding of concepts of the mind-independent world is not provided simply by our having perceptual experiences into which, as it were, mind-independent objects float; it is provided by our attention to the mind-independent objects we experience. Sometimes we have the right to take it that we are experiencing one and the same mind-independent object again, as we do when trading on identity, without any auxiliary argument to establish the truth of an identity proposition. And sometimes we do need some auxiliary argument before we can take it that we have one and the same thing again. To understand the distinction between those cases we have to look at the structure of conscious attention. The fundamental point to bear in mind here is that attention is itself a relation between the observer and the scene viewed. And in characterizing this relation, we have to describe the causal structure relating the objects and properties that the subject is experiencing.

To illustrate, let me take a particularly simple example where it is particularly clear what is going on. Suppose we consider the kind of diagram used for tests of color vision, in which a target object, say the number 5, is constituted of blobs of various sizes and luminances, on a dappled or brindled field of blobs similarly varying in size and luminance, so that the only systemic way in which the 5 is differentiated from its background is by hue. If someone can see the 5, then they do have visual experience of color; that is the assumption on which the color test is used (the Ishihara plates).
When someone can see the 5, the color and location of the object are the properties of it that are causally responsible for the object being singled out at all. That color has to be used to single out the object in visual experience is the whole point of the test; there is nothing other than hue that could causally differentiate the thing from its background. Of course location is being used, as become evident if you consider a variant on the Ishihara plate that has two figure 5s, of the same hue as one another, at different places on the same dappled or brindled background. All that differentiates the two 5s is their location; but you have absolutely no difficulty in focusing on one rather than another of the two 5s. So there is a contrast here between hue and location on the one hand, and shape on the other. Hue and location are causally involved in allowing you to see the object against its background. But the shape of the thing—whether it is a 5 or a 3 or something else—may be playing no such causal role. You would still be singling out the object on the basis of its hue and location whatever shape it had.

The fact that color and location are playing this causal role in your visual experience does not mean, however, that you have any knowledge of the color or location of the figure. The capacity to see the object is obviously in principle independent of the ability to give a verbal report of its color, for example, and independent of the ability to engage in color induction (“the red berries I have had all made me sick, so all red berries will probably make me sick”), or the ability even simply to match objects of different colors or to arrange them by color (for example, from darkest green to lightest green). And in fact children seem to have color vision in place as early as three or four months, an age that seems quite likely to predate any explicit knowledge of the colors of things. The function of color vision in animals is most importantly to allow them to see objects against their backgrounds. If color vision serves that function, the color may be of no further interest, and certainly not of interest for its own sake. So the causal role of a property in allowing you to see an object has to be differentiated from the causal role of a property in generating perceptual knowledge that the object has that property.

So suppose you can see the figure 5 against its background, and you form the judgment, “That figure is a 5”. The simplest form of the relational analysis describes the situation by saying that you are related by the two-place relation of consciousness to the figure 5, and to the properties of color, location, and shape. But what I have just been arguing is that we can give a more informative analysis of the situation by distinguishing between the kinds of causal roles played by the properties of color and location on the one hand, and shape on the other. We could find state this distinction by talking about the “point of view” from which the scene is being observed, or we could put it in terms of adverbial modification of the kind of experience of the scene one is having. And this kind of causal structure in one’s observation of the scene is what underpins one’s selection of a figure as the target of one’s attention, and a particular dimension—shape or orientation or whatever—of the object as the aspect of it about which the experience can generate knowledge.

Of course, this is a simple example, but the point I am making here seems to me quite general. Whenever an object is differentiated from its background, there will have to be some account of the characteristics of the object that, together with its location, are causing the object to be experienced as figure on ground. This is the realm of classical Gestalt psychology, or more recently, work on perceptual organization. And there will have to be some account of the dimensions of the object to which one is attending, or in other words, which properties of the object are directly implicated in knowledge that the object has them.

When we are characterizing your perceptual experience of an object, then, it will not be enough simply to say which object you are experiencing; we will also have to say which properties are being used to differentiate the object as figure from ground in your experience (color and location in our above example; but there are endlessly many further possibilities). This is a matter of characterizing the attentional structure of your experience. Our concern was with the validation of reasoning that relates to the identity of the object across time, or across modality, or across person. What we can say, on the relational view, is that for perceptual experience to underwrite such reasoning, it is not enough that the perceptual experience should relate to a single object throughout. We also have to take into account the way in which the object is being singled out in experience.

We can describe the way in which the object is being singled out by specifying the characteristics that are being used to differentiate the object as figure from its ground (color and location in our above example). Notice that this is not a matter of replacing the reference to the object in a description of the experience with a mention of these distinguishing characteristics. Rather, the experience is described as an experience of that very object, it being distinguished by those characteristics (such as color and location). Formally, we could incorporate those characteristics into a specification of the “point of view” from which the object is being observed, or we could think of them as part of a complex adverbial qualification of the way in which the object is being experienced.

In saying how perceptual experience validates the patterns of reasoning that we use concerning mind-independent objects, we have to reckon in the ways in which we single out the objects we perceive. These will play a role in determining when it is legitimate to trade on identity in one’s use of a term referring to the experienced object, and in providing the bases from which one can argue to establish the truth of identity statements relating to the experienced object. We will also have to reckon in the factors that allow us to keep track perceptually of a single object over a period of time, across modality and across speakers. Again, these factors will not replace the role of specification of the object itself in a characterization of the experience; rather they supplement the specification of the object, and provide a fuller description of the perceptual experience.

4. Other Minds and the Relational View of Experience

Thinking of sensory experience in terms of the relational view of experience is quite an alien exercise for many readers; so much so that it may be helpful if in this section I set out the bearing of this view on some more familiar ways of thinking of sensory experience. Our general question is whether phenomenal consciousness plays any role in our having a conception of the world around us, and if so, what that role might be. There are a number of aspects of perception that we might reasonably want to separate from the phenomenal or sensory awareness that I want to focus on. There is, for example, the mere fact that perception involves some kind of representation in the brain. In visual perception, for example, the visual system in the brain generates some kind of representation of one’s surroundings. In principle, this could happen whether or not there is sensory awareness of your surroundings. There are, for example, types of subliminal perception, in which we seem to have differential reactions to various stimuli, which seem to involve representation of them, without sensory awareness. Most strikingly, there is semantic activation without conscious identification. Presented with a word just below the threshold of awareness, you might respond in a way that seems dictated by the meaning of the word even though you are not aware of the presence of the word. In such cases it is hard to explain what is going on without assuming that you have some brain representation of the word itself, even though you have no awareness of it. Representation is one thing, and awareness is another. Sensory awareness is what happens when, in Nagel’s (2002) famous phrase, there is something it is like to perceive.

This notion of there being “something it is like” to perceive a thing needs, though, to be treated with some caution for our present purposes. The problem is that it is natural to give the notion an “internalist” twist that makes it difficult to achieve understanding of the epistemic role of consciousness. Let me explain first why the internalist twist can seem natural. Nagel introduced this notion in the context of imagining how the world is from a bat’s point of view. He remarked that one could know all there is to know about the physics of the bat and of the surroundings of the bat without knowing the one thing that seems most intriguing and elusive; what it is like to be a bat. Now when you put it like that, “being a bat” is something that seems to involve only the bat itself. So imagining what it is like to be a bat should involve only aspects of the world that are internal to the bat itself. But this is not way we usually understand the phrase, “what it is like”.

Suppose that your job is to design the stage set for a forthcoming performance. You have reached the point where you are on the stage surrounded by various pieces and a lot of machinery so you can manipulate your provisional set. However, the auditorium is being repaired so you can not sit in the stalls and view your set directly from there. You have to imagine what your set will be like from there. Will the red and gold you are using be a bit overwhelming, or will the distance have a subduing effect so that it merely seems sumptuously ornate? The set is a bit complicated. Will it seem cluttered, or is its spatial organization lucid enough that it will be evident what is going on? Will the actors be hidden from the spectators by the set, or will it frame them well? More briefly, what will it be like from, say, the rear stalls? That is the imaginative exercise you have to engage in. There is obviously no difficulty of principle about this, though some people will doubtless be better at it than others. Also, though, notice that this is a relational, or real-world exercise of the imagination. You are imagining what the set will be like from various vantage points in the auditorium. This is relational. It involves the physical stage set itself, the perceiver in the audience, and a relation between them.
For a philosopher who thinks about the conscious life in purely internalist terms, it will seem that this relational exercise misses the key thing. This is not a matter of imagining what the set will be like from various perspectives. To get onto the conscious life proper, you have to engage in a purely “internalist” exercise: imagining the mental life of the spectator in isolation from any of the surroundings, regarding the stage set itself as merely a causal prod to the production of inner experiences.
If you think of the project in this way, it is likely to strike you not merely as a skilled exercise that some people might be better at than others. The thing is likely to strike you as altogether impossible. After all, the spectrum of the individual in the stalls might be an inversion of yours, so that the sensations they have when viewing red and gold are more like the sensations you have when viewing green and grey. Or maybe they are nothing like any of your color sensations at all. Perhaps they are more like the sensations you have when listening to the tones of an organ. Or perhaps they are frankly alien, like nothing in your experience. How could you know? A stage-set designer struck by this thought would really have no way of proceeding. Perhaps God can know what the arbitrary individual in the stalls would experience, but it may be altogether beyond the ken of the humble set designer.

On a relational view of experience, there is no such “deep” inquiry into the sensory experience of the other to engage in. In the case of ordinary perceptual experience, there is no such thing as the “inner life” of the Other, considered in isolation from its relations to its surroundings. There is only the “surface” enquiry that set-designers and other visual artists and technicians routinely engage in. This simply does not require grappling with the unfathomable. This is the exercise of imagining, for example, what the set is like from the rear stalls. This is certainly a question about the conscious life of the perceiver; it is a question about what kind of sensory experience the audience will enjoy, and this impacts the kind of aesthetic experience the audience will have. But as I have said, it is a relational question. It is a question about the set itself, and the audience’s experiential relation to the set.

In the case of the bat, there is an analogue to the stage set designer’s practical question, but it seems, on a relational view, altogether unanswerable using only the resources of an ordinary human. The designer who wonders what the theater will be like from the point of view of, let us say, the bats hanging from the rafters, really may find that an understanding of this is beyond his powers. That is not because his question is an intrinsically unanswerable one about the internal mental life of another. It is rather that in this particular case, since it is a bat we are dealing with, many of the things that the bat experiences may not even be visible to the designer, and even if they are visible, the designer may have no idea which things they are. So relationally imagining the bat’s sensory experience may be impossible simply because one has no sense of which things the bat is experientially related to. In the case of the bat, it is very difficult for humans to imagine occupying the viewpoint of such a perceiver.

To say all this about our knowledge of another human’s sensory experience is not to deny that there is such a thing as depth in one’s understanding of another person’s mental life. Borges somewhere introduces one of his characters by saying, “Like all men, he was fathomless,” and few people would say that they do not recognize that sense of the endlessness of the probing it is possible to do into the inner life of another person, male or female. The present point is only that it is quite wrong to suppose that the right location for that sense of depth is in the characterization of sensory experience. If anything is a superficial fact about someone else’s mental life, it is the nature of their sensory experience.

I want now to give another way of indicating what I mean by “sensory experience.” This is to give a slight twist to Frank Jackson’s example of a person who lives in an entirely black-and-white environment, and learns all there is to know about color and color vision from black-and-white texts and diagrams. Jackson’s (1983) point was that this person, Mary, may have all the relevant physical information about her world, yet still learn something when she steps from her black-and-white room into the world of color. The slight twist I want to give to this poignant story is that whatever Mary learns, it is not in virtue simply of perception that she learns it; she learns in virtue of her sensory experience of her surroundings. There is a dispute in the literature on blindsight as to whether it is possible for blindsighted subjects reliably to make color discriminations on the basis of perception without awareness. For the purposes of our thought experiment, we can suppose that Mary is capable of discriminating between colors on the basis of perception without awareness. Even if this is true, it does not in any obvious way provide her with more information about her world than she had on the basis of the purely physical information given in her black-and-white texts. What she needs, to learn something, is sensory experience of the colors. This is not merely a matter of being able to make discriminations between colors on the basis of vision; we ordinarily have something more than that, the phenomenal blaze of colors themselves.

In terms of this example, we can see one of the key questions about the role of experience in our knowledge of the world. The question is whether what Mary learns on the basis of sensory experience of color is something about the nature of sensory experience itself. Since Jackson stated the example, it has always been taken that all that Mary can learn from her sensory experience of color is something about sensory experience of color. If you state this idea in full generality, it gives us the basis of Berkeley’s Puzzle. The idea is that Mary’s experience of color can provide a basis for the concept of the experience of color itself, and not much else. She could not have had any conception of what it is to experience scarlet before she stepped into the world of color, and afterwards she has learned what it is to experience color. More generally,

Sensory experience provides only for the concept of sensory experience itself.

You might argue that there is also another kind of “concept formation” that does not demand a sensory encounter with the phenomenon itself. You might argue that this other kind of concept formation demands only that you have been causally affected in one way or another by some distal stimulus; perhaps in this second sense that is all that is required for you to “have the concept” of the distal stimulus.

At this point we can already see something of the force of Berkeley’s Puzzle. You might already remark that it is hard to resist the sense that there is a robust notion of “knowing what the thing is” that you have for sensory experience, and that never applies to your knowledge of anything else at all. It is only a misleading compliment you pay yourself to say that you ever have the conception of anything else at all. And once you have reached this point, you are in the grip of Berkeley’s Puzzle. To have the concept of anything at all, including the concept of a mind-independent object, you have to have experience of the thing. But experience can provide only for the concept of experience itself. So we cannot, in any real sense, form the concept of a mind-independent object. We can form the concept only of experience itself.

My general point about Jackson’s Mary is that we can put the emphasis in a different place than it is usually put. Discussions of Jackson’s Mary usually put the key role of “sensory experience” as being what Mary learns about; they take it for granted that what Mary acquires on stepping from her room is some conception of sensory experience, and then they go on to argue about whether this fact is consistent with physicalism. My present point is that it is not obvious that what Mary learns about is sensory experience itself. Rather, our starting-point should be that it is in virtue of her sensory experience that Mary learns something. But it is not at all obvious that what she learns about is sensory experience itself. Rather, she may be learning about the color properties of the objects in her surroundings, even if she has no conception of mental states at all. The idea that sensory experience provides only for the concept of sensory experience itself is much more problematic than it is usually taken to be. Suppose we go back to the question: what does Mary learn when she steps from her black-and-white room into the blaze of color? Suppose that Mary does not so much as have the concept of a visual experience. It is sometimes suggested that people with autism have difficulty with the very concept of mind. Suppose we have a subject for whom something like this diagnosis is correct. It never occurs to her that other people have sensory experiences. It has never even occurred to her that she has sensory experiences herself. Or even if it has crossed her mind at some point in the past that others, and she herself, have sensory experiences, the phenomenon is one that she finds of no interest, and in practice she never directs her attention to questions about what sensory experiences people are having. So when this Mary steps out from her black-and-white room, whatever she learns about, she does not learn about sensory experience. She is interested in the characteristics of the concrete objects around her. She has, however, no interest in the psychological. She is interested only in the material characteristics of the physical things around her. Does our Mary learn anything when she steps out from the room? On the face of it she does. It will certainly seem to her that she does learn something. She will take it that she learns about a characteristic of the objects around her; a characteristic that does not have anything particularly to do with sensory experience except that she gets knowledge of it from the use of sensory experience.

One way to develop this point is to consider the case of someone who is a bit like Mary, only her case centers not on colors but on shapes. It is a bit harder to get this case stated. It is relatively easy to think of someone who occupies an entirely black-and-white environment. It is a bit harder to think of someone who occupies an environment devoid of shapes. The point is that someone who encounters only black-and-white objects does not seem to have the resources to define any other color concepts at all. But it is not quite clear how we could have a suitably non-spatial environment. On the face of it, if our subject encounters spatial characteristics at all she will have the resources from which to define spatial concepts; or at any rate, if something is lacking, it will not be something spatial that is lacking. But we can get the effect we want by again considering the direction of our subject’s attention. Suppose that our subject learns all about shape properties from purely textual or verbal information—no diagrams or photographs. And though she has ordinary spatial perception, she simply never attends selectively to the shapes of things. So it never occurs to her that the shape properties about which she has read so much are properties that are visibly possessed by the objects she perceives. What, if anything, does she learn when she finally makes that connection, when she finally grasps that the properties about which she has read are the same as the visible properties to which her attention has finally been drawn? On the face of it, our character—call her Bridget—will learn something. She will take herself to have learned something. You might say that what she has learned is something about mental states—she has learned something about what kind of visual experiences these properties produce. But we can suppose that Bridget has the same lack of interest in mental states generally, and visual experiences particularly, as our Mary. So whatever she learns, it is not something about visual experience. Bridget will nonetheless take herself to have learned something. She will have learned which properties those are that her texts concerned. On the basis of her sensory experience, she will have learned something about a physical characteristic of concrete objects. And notice that she would not have learnt this from a mere capacity to engage in blindsight-style reliable guessing as to which verbal shape-names apply to which objects in her vicinity. Sensory experience was really required for the learning here.

Let me give one last way of setting out the notion of “phenomenal awareness” or “sensory experience” that concerns me here. This is to appeal to Block’s (1997) distinction between access and phenomenal consciousness. The distinction here is between a notion of “access” consciousness that is defined in terms of the architecture of perceptual representations, and a notion that is not so defined. A representation is said to be “access” conscious if it is “poised for the rational control of thought and action”. I hope it is evident that our question does not have to do with the epistemic role of access consciousness. Our question is whether phenomenal consciousness makes a difference to one’s concepts of one’s surroundings. What is phenomenal consciousness? In giving his general characterization of the notion, Block relies on Nagel’s formulation: there is something it is like to be phenomenally conscious. So the comments made above apply here too—phenomenal consciousness may be a matter of how the world is grasped from a particular point of view, rather than a matter of purely internalist states. For example, the blindsight subject characteristically does not have the same internal functional architecture as the ordinarily sighted person; but seems to be missing something more, namely an ability to experience the objects and properties in the environment. What the blindsighter misses, in the blind field, is the kind of experiential contact with objects and their properties that could play a role in justifying the use of particular patterns of reasoning in connection with them. Of course, the blindsighted subject may formulate descriptions that uniquely specify objects in the blind field: “the object on my left”, “the thing the experimenter is manipulating”, and so on. But the blindsighted encounter with an object in the blind field is not enough to allow the subject to formulate the simple, perception-based demonstrative, “that thing”. The relationalist analysis applies to phenomenal consciousness. It says that the phenomenal consciousness involved in ordinary perception is a matter of the observer being experientially related to the scene observed, and that this is the basis of the observer’s knowledge of the objects and properties in question.

5. Sensations and Representations

The literature on sensory experience has tended to suppose that sensory experience must be characterized not in relational terms, but as a matter of having perceptual representations of one’s surroundings, or as a matter of having perceptual sensations. Neither of these views is particularly persuasive, taken on its own, so the literature largely consists of devotees of one side pointing out the problems with the other side, and in reaction, a massive and complex collection of compromise views, with some markedly radical positions from uncompromising sensationalists or uncompromising representationalists also being staked out. Berkeley’s Puzzle writes large the difficulties with these views; and indeed, the difficulty with the idea that sensationalism and representationalism are the only alternatives when it comes to the characterization of sensory experience. Suppose that we accept the dichotomy between sensation and representation in describing experience. What must sensory experience be, if it is to ground our conception of mind-independent objects? It is natural to think that sensory experience is really a matter of having sensations of one kind or another. But on the face of it, just having a sensation can not, in the first instance, provide you with information about anything except the sensation itself. You might, of course, form conjectures about the hypothesized causes and effects of the sensation. But a mere sensation in itself could not provide concepts of the objects and properties around you.

Alternatively, you might think that having a sensory experience is a matter of representing the world in a particular way. That seems to make it much more evident how sensory experience could, as it were, provide you with a window on the world. If your perception represents things as being thus-and-so, maybe that could explain how you know that things are thus-and-so. And if your experience represents the objects and properties around you, that can explain how your experience provides you with knowledge of the objects and properties around you, and so explain how you can have concepts of those objects and properties.

Suppose we ask how it is that sensory awareness, on the representationalist analysis, can provide you with an understanding of concepts: knowledge of the things and properties around you, knowledge of which objects and properties there are in your surroundings. The proposed answer is: this is a matter of having representations of those objects and properties, representations that figure in the content of your sensory awareness. Here we face the fundamental problem that you could have those very representations outside the context of conscious awareness. So if it is the representations that are providing the knowledge of objects and properties, we have as yet no explanation of how sensory experience might be doing any work in providing the knowledge. Moreover, it is in any case not obvious how having representations of colors or shapes, for example, could explain your knowledge of what colors and shapes are; representation of color or shape already seems to presuppose your grasp of concepts of color or shape. So it seems to get things the wrong way round, to say that your ability to represent colors and shapes explains how you know what colors and shapes are. You might argue that perceptual representations have a kind of representational content, “non-conceptual content”, that does not presuppose a grasp of concepts of ordinary objects and properties. But the more we stress that perceptual content is “lower-level” than conceptual content, the harder it becomes to see how a grasp of ordinary concepts could somehow be generated out of this kind of content. It is hard enough to define one set of concepts in terms of another set of concepts; there is no obvious way in which conceptual contents could be explained in terms of some quite different kind of content

On the one hand, it seems compelling to common sense that sensory experience has a fundamental epistemic role to play; sensory experience is our window on the world. On the other hand, it is not quite easy to see how that can be so. If we think of sensory experience as a matter of having sensations, then it is hard to see how sensory experience can be providing knowledge, in the first instance, of anything but those sensations themselves. If you think of sensory experience as a matter of representing how things are, then it is not obvious how awareness can have a fundamental epistemic role to play, since you can have representations without awareness; why would not representations without awareness provide just as good epistemic access to objects and properties? Moreover, the use of representations seems to presuppose, rather than to explain, the very knowledge of things and properties that we are trying to explain. The natural thought is that we should combine the representationalist and sensationalist approaches. Perhaps we can say that our representations of the mind-independent world are grounded in sensational aspects of perception. But now we face Berkeley’s argument. Put in terms of representation and sensation, his argument is this:

(1) There is a distinction between representational and sensational aspects of perceptual experience.
(2) All the representations we can form have the contents they do in virtue of their connections to the sensational aspects of experience.
(3) Representations that derive their meanings from their connections to sensation can only relate to how things are with sensations.

It seems to follow from this that we cannot form representations of a mind-independent reality.

It seems to me that what is problematic is the idea that the non-representational aspects of experience are to be thought of as sensations. As I have said, it seems to me arguable that the non-representational aspects of experience are not constituted by sensations. They are, rather, constituted by the experiential relations that the subject, occupying a particular point of view, stands in to the objects and properties in the environment. When we restate Berkeley’s assumptions in these terms, we have:

(i) There is a distinction between representational and relational aspects of perceptual experience.
(ii) All the representations we can form have the contents they do in virtue of their connections to the non-representational, relational aspects of experience.
(iii) Representations that derive their meanings form their connections to non-representational, relational aspects of experience may relate to how things are in an objective, mind-independent world.

The premise that would now be regarded as most obviously problematic in Berkeley’s argument is his (2). The argument for (2), though, is that only an approach that connects representational content to perceptual sensation can do justice to the sense in which representational content enters into the subjective life of the perceiver. Recasting the premise as (ii) aims to recognize this point.

Accepting premise (ii), you can still find a place for causal considerations in a theory of content. For causal considerations will matter for the existence of the relation “perceives” between subject and object, or subject and property; it is not to be supposed that what one is experiencing is a matter independent of some underlying level of physical and causal facts. Causal considerations matter because they have a constitutive role in determining what one is experiencing, and in consequence of that they have an impact on what one can represent or think about.

This gives us a way of recognizing what is still controversial and correct in Berkeley’s argument, while also acknowledging that our conscious experiences can ground thought about an objective, mind-independent world.

ACKNOWLEDGEMENT

This paper is excerpted from my contribution to a book jointly authored with Quassim Cassam, Berkeley’s Puzzle, that is in preparation. I am grateful to Quassim Cassam for comments on earlier drafts.

REFERENCES

Berkeley, G. 1734/1975. A Treatise Concerning the Principles of Human Knowledge. Reprinted in Berkeley: Philosophical Works, ed. M.R. Ayers (London: Everyman): pp. 62-127.

Block, N. 1995. On a Confusion About a Function of Consciousness. In The Nature of Consciousness, ed. N. Block, O. Flanagan, and G. Guzelder (Cambridge, MA: MIT Press).

Jackson, F. 2002. Epiphenomenal Qualia. In Philosophy of Mind: Classical and Contemporary Readings, ed. D. Chalmers (New York: Oxford University Press).

Nagel, T. 2002. What is it Like to be a Bat? In Philosophy of Mind: Classical and Contemporary Readings, ed. D. Chalmers (New York: Oxford University Press).