Reference and Consciousness. By John Campbell. Oxford: OUP. 2002.


What is the role of conscious experience in action and cognition? John Campbell’s answer in Reference and Consciousness begins from ideas he thinks are part of common sense: When our actions are directed toward particular things – as it is when we grab our keys, or lift forks from plates– these actions are guided by visual experience. We see where to reach for keys or fork, and only then are able to do it. Similarly for the case of cognition: in cases where experience is limited, such as blindsight, cognition suffers as well. Consider a blindsighter who can reliably point to the person a normally-sighted speaker is talking about whenever she uses the expression “that woman”. Even if the blindsighter points correctly all the time, she does not understand the speaker’s use of “that woman”. Common sense (according to Campbell) thus finds a distinctive role for conscious experience in action and cognition, in opposition to the view that everything essential to action and cognition could proceed perfectly well without any conscious experience at all. In this way, common sense opposes epiphenomenalism about experience – the view that experience has no causal role to play with respect to cognition or action.

A central thesis of the book is that conscious attention is needed to understand what (some basic) uses of demonstrative expressions refer to. “When I say that knowledge of reference is provided by conscious attention to the object, this is a description of what knowledge of reference is” (3). After a brief defense of this thesis, Campbell uses it in the bulk of the book as a constraint in accounts of what conscious experience and demonstrative reference must each be like. Campbell relates this role for conscious attention to many other topics, arguing for theses concerning the role of sortals in demonstrative expressions, Fregean senses of demonstratives, joint attention, uses of demonstratives anchored to their referents by memory, anti-realism, indeterminacy and inscrutability in reference, and the distinction between dispositional and categorical properties.

So Campbell’s strategy is to begin with a defense of supposedly common sense views about the role of experience in action and cognition, and consider what else must be true if these views are. A great deal in the book thus turns on the central idea that the blindsighter cannot understand the use of a demonstrative such as “that woman” despite reliably pointing to its referent. To defend this idea, Campbell invokes an intuition that understanding is missing (9). For some readers this verdict will raise flags, since the understanding in question is knowledge-who, and attributions of such knowledge-who are notoriously sensitive to purposes. Suppose the speaker tells the blindsighter, “That woman wants to be pointed out. Point to her”, and the blindsighter does, after first asking ‘Which woman?’, then being told to guess. It does not seem crazy to ascribe understanding, and indeed knowledge to the blindsighter: “He understood the command” and “He knew which woman to point to” don’t seem obviously false.  It is further step, though a plausible one, to suppose that for the purpose of pointing, the blindsighter does understand the demonstrative; but for the purpose of picking out in a line-up, he doesn’t  - and if this is so, then the blindsighter isn’t missing out on understanding; rather he simply shares with the rest of us the fate of having our knowledge-who depend on our purposes.

Campbell, however, has a more specific notion of understanding and knowledge of reference in mind. One understands the use of a demonstrative (or equivalently, knows what it refers to) just in case one is justified in two kinds of transitions: first, from subpersonal visual representations to demonstrative utterances (or their analogs in thought) of the form that F is G (e.g., from visual system’s representation of an object at location L to an utterance of  That cup contains water); second, from such utterances or thoughts to actions on the referent of the demonstrative (e.g., from an utterance of That cup contains water to grasping the cup) (35). For Campbell, the most basic role for experience is to justify these transitions. It is supposed to be simply counterintuitive that such justification could be conferred without experience, merely by reliably arriving at true utterances (or thoughts) and reliably succeeding in actions. Reliabilism about this kind of justification is dismissed at the outset for disrespecting the bedrock intuition that, without experience, such justification is missing.

Campbell somewhat overstates the strength of this intuition. Though powerful, to say that the intuition is part of common sense goes too far. There is a philosophical debate about justificatory reliabilism in part because the intuition that the blindsighter is justified in (say) thinking what he does has some force. 

In chapter 3, Campbell refines the account of the functional role of attention in cognition and action in light of empirical results concerning anoxia, blindsight, and various illusions. The refined role for conscious attention is that conscious attention to a substantial object (person, tree, etc) causes subsequent information processing about that object. Call this role ‘targeting’, and distinguish it from the (putative) role of experience in understanding what a use of a demonstrative refers to. Targeting is supposed to happen both in normal cases and cases where experience is degraded or falsidical. For instance, in anoxia, a subject lacking both visual experience and explicit beliefs about the orientation of a slot in a block is nonetheless able to post a card through it. Campbell’s view is that when anoxic subjects (such as DF, discussed by Milner and Goodale) visually attend to the slot, their conscious attention causes their visuo-motor system to process information about its orientation, even though this information does not itself seem to be represented in experience.[1] To take another example, in the Ebbinghaus illusion, two differently-sized disks appear to be the same size, yet the false appearance does not influence the grip one sets when reaching for them. According to Campbell’s second proposed role for conscious attention, when subjects attend to the Ebbinghaus disks, their attention causes their visuo-motor systems to process information about the disks’ size. 

In defending the claim that conscious attention causes information processing about the objects attended to, Campbell focuses on cases in which action is not thrown off by falsidical or degraded spatial content of experience. In these cases, it is not the exact spatial content of the imperfect experience that explains why one moves one’s body in action the way one does: if those spatial aspects of action were guided by how the imperfect experience presents things, then subjects would reach differently for disks that are in fact the same size, and DF wouldn’t be able to post the card through the slot after all (51-53). So the specific spatial content of experience does not (in these cases) guide action. Campbell concludes from these cases that the spatial aspects of action are never explained by the exact spatial content of experience; Christopher Peacocke is criticized for allegedly supposing otherwise in Sense and Content (57). Instead, Campbell claims, conscious attention simply causes subsequent information processing, and the latter is what guides action. (E.g., it is DF’s subpersonal information processing that allows her to find the slot for the card). Campbell thus reaches his conclusion about the role for experience in action generally, by generalizing from the role of ‘imperfect’ (i.e., falsidical or degraded) experiences in action.

Here it seems that the falsidical, rather than the degraded experiences, are firmer ground for the generalization. The Ebbinghaus illusion is a normal visual experience; there doesn’t seem to be reason to think that the information processing operative in the visuo-motor system when one views Ebbinghaus disks differs from what’s operative when one doesn’t view them (plenty of normal visual experiences are illusory in some way). In contrast, to generalize from the case of anoxia to normal cases, what has to be shown is that the visuo-motor processing left intact is the same kind of processing as usually operates, rather than a kind that kicked in with the onset of the deficit. 

In any case, given that Campbell thinks conscious attention plays two roles in cognition and action – targeting, and enabling the subject to understand uses of demonstratives - Campbell has two battles with epiphenomenalism, one for each of these roles. It is not clear whether Campbell wins on targeting. In blindsight, targeting proceeds without the help of conscious experience (let alone conscious attention), so everyone should agree that the epiphenomenalist is correct in claiming that some targeting processes are not caused by conscious attention. But if the same targeting processes are at work in blindsight and in normally sighted subjects, then conscious attention appears not to be a part of it after all. Perhaps there are empirical grounds for the view that targeting in blindsight operates differently from how it operates in normally sighted subjects, so that there is a kind of targeting for which conscious attention is needed, and a different kind, operative in blindsight, for which it is not needed. But this is not a line that Campbell presses. Without some way to block the generalization from blindsight to normal cases, for all Campbell says conscious attention is not needed for targeting. 

The other putative role for experience in cognition - that conscious attention to a referent is needed to understand uses of demonstratives – is the one that is supposed to provide a great deal of positive and negative philosophical mileage, ruling in some views and ruling out many others. One area in which this idea is supposed to bear philosophical fruit is the theory of the nature of conscious experience. Here, however, the constraint is not merely a necessity claim (i.e., the claim that experience is necessary for understanding demonstrative reference), but rather the explanatory claim that “experience is what explains our grasp of substantial objects” (120).  This claim is supposed to constrain theorizing about phenomenal character, and it is supposed to be evident from considering the blindsight example. Campbell calls the theory of experience he favors ‘the Relational view’. This view holds that ‘the [perceived] object itself is a constituent of the experience’ (p. 130), so hallucinations in which no object is perceived are not the same kinds of experience as cases of perception, even if they are subjectively indistinguishable from such experiences. The relational view contrasts with views that allow that hallucinations and veridical perceptions are the same kind of experiences, differing only in their external relations to the environment. Only the relational view, Campbell claims, respects the constraint that experience explains one’s knowledge of uses of demonstratives refer to, whereas that constraint is supposedly violated by the view that two experiences of (say) seeing two qualitatively identical cups may have the same phenomenal character and the same content.

Do non-relational views really disrespect the fact (assuming it is one) that seeing the cup enables you to know which particular thing you are talking about when you say “that cup”, pointing to a cup before you? According to one non-relational view, both experiences share existentially quantified contents expressed by ‘There is a cup at location l’. Here is Campbell’s case that his constraint is violated:


The whole point of the view is to insist that consulting perception will only provide you with a number of existential propositions, to the effect that there is, for example, a cup of a certain type on a tray, without ever getting down to the brass tacks of telling you which cup it is that is on top of which tray. So no amount of looking to see could provide you with knowledge of which cup is being talked about. It is therefore entirely obscure how you could have achieved knowledge of which cup is in question. (124-5).


Another non-relational view holds that the content such experiences is better characterized by ‘that is a cup at location l’ (where this content is shareable by experiences of different cups), rather than by an existentially quantified sentence. Campbell criticizes this version of the view on similar grounds: “all that is within the perceiver’s subjective life is the demonstrative element itself”, and so an experience with such content “cannot by itself, therefore, distinguish between presentation of one object and presentation of another…It is, therefore, opaque how the demonstrative element could provide the subject with an understanding of the demonstrative term.” (125). 

 A proponent of either of these non-relational views could agree that the repeatable part of the perception considered apart from external conditions does not “provide [the subject] with knowledge” of which cup is in question, but hold that the repeatable part when had under the right external conditions does. (This view is even suggested by the quote indented above, where Campbell talks about consulting perception, rather than consulting simply what’s ‘within the perceiver’s subjective life’: by the lights of the views being criticized, these can come apart). It is open to the proponents of these non-relational views to hold that whether experience gives you knowledge of reference depends not just on its phenomenal character or content, but on the external circumstances in which the experience is had. This move deserves discussion. It isn’t hugely theory-laden; in fact, it is a starting point in debates in epistemology: there is a strong intuition that you don’t know there’s a barn in front of you even when you’re seeing one if you’re in fake barn country. But the move is ignored. Since it seems compatible with Campbell’s explanatory constraint, that constraint seems less powerful than Campbell supposes. 

Campbell’s book is a set of lively discussions of diverse topics, threaded together by their bearing on a central question in the philosophy of mind. It is valuable for focusing on the appeal of epiphenomenalism about experience from the point of view of some cognitive science, and on possible replies to this position. Much of the literature on epiphenomenalism about experience approaches the issue by considering metaphysical questions about causation and physicalism, or on the relation between phenomenology and representation in experience itself.[2] Campbell’s book instead considers the nature of representation in language and cognition more generally. This is a new approach to discussions of epiphenomenalism. Its pursuit in Reference and Consciousness reveals how many important issues in metaphysics, the philosophy of mind and language, epistemology and empirical work on perception intertwine.[3]



                                                                        Susanna Siegel

Harvard University


[1] At least, it is not available for report.     

[2] Dretske argues that the function of experience is representation, in “What Good Is Consciousness?”, reprinted in Perception, Knowledge and Belief, Cambridge: Cambridge University Press, 2000, 178-92.

[3] Many thanks to Imogen Dickie for helpful discussions.