Dilworth's Functional Consonance

In his paper, “Perception, Introspection and Functional Consonance”, Dilworth attempts to provide a broadly functionalist account of first-person authority with respect to how things perceptually seem to an agent. The account is functionalist in the sense that it individuates cognitive states in terms of their role in the aetiology of a disposition to engage in a certain kind of classification behaviour. For example, if I perceive that X is red or I believe X is red, then my perceiving or believing are to be unpacked in terms of my disposition to sort X as red in the relevant classification task (i.e., to engage in red-classification behaviour). When my perceptual experience and belief match in terms of classification behaviour, they are said to be “consonant” with each other. Moreover, Dilworth holds that in any given situation, S, it is logically impossible for an agent to be disposed to behave in two mutually exclusive ways in response to S. It follows that if an agent has both a perceptual experience and belief in response to a given situation, the experience and belief must be consonant with each other. This leads Dilworth to postulate what he refers to as the “perceptual consonance principle”:

(PCP): If one is having at time t a perceptual experience concerning the F-ness of X, and if at that same time t one is also having a perceptually derived belief concerning the F-ness of X, then the experience and the belief must be consonant with each other.

Unfortunately, it is possible to construct a counterexample to (PCP). Consider a case in which an agent is given the task of classifying objects as straight or bent. Moreover, let us suppose that the agent is unfamiliar with the phenomenon of refraction. Looking at a partially submerged stick the agent has the visual experience of the stick being bent. Given Dilworth’s dispositional model, this entails that the agent is disposed to classify the stick as bent. Suppose further that the agent slides her fingers down the length of the stick, giving rise to the tactile experience of the stick being straight. By Dilworth’s lights, this entails that the agent is disposed to classify the stick as straight. Since it is possible for the agent to have the visual experience that the partially submerged stick as bent (at time t) and have the tactile experience of it being straight (at t), it follows that an agent may be simultaneously disposed to engage in conflicting classification behaviours. Furthermore, we can imagine that the agent forms the perceptually derived belief that the stick is straight (based on her tactile experience). In such a case, the agent would have a perceptual experience concerning the shape of the stick (a la sight) and a perceptually derived belief concerning the shape of stick (a la touch), without the experience and belief being consonant with each other.

UPSHOT: What must be added to (PCP) is a restriction to a single sensory modality, and not simply a restriction to a given time or situation. However, as far as the paper under consideration is concerned, Dilworth fails to provide us with the theoretical tools we need for such a restriction.

Dilworth appears to anticipate this objection in his discussion of the Muller-Lyer illusion; a case in which a pair of equal vertical lines (A and B below) appear to have different lengths.

According to Dilworth, one can be said to perceive the lines as being of different lengths because one is temporarily disposed to classify them as such. However, this perceptual disposition is quickly displaced by one’s prior belief that the lines are actually the same length. Moreover, Dilworth points out that this offers no counterexample to his claim that there cannot be conflicting perceptual dispositions since the “relevant knowledge that the lines are actually the same length is clearly not a belief that is perceptually acquired...” He summarises the point as follows:

[W]hat we have in such cases is not a conflict of perceptual dispositions—which has already been shown to be, strictly speaking, impossible—but instead a refusal by a perceiver to believe what she would otherwise believe on ‘the evidence of her own eyes’, so that the temporary or initial consonant belief that the lines are of different lengths is rejected in favour of a longer-term belief based on prior knowledge.[1] (Italics mine)

CAVEAT: Insofar as Dilworth’s functionalist analysis commits him to the thesis that being disposed to engage in classification behaviour is a necessary condition for perception, his claim that one is only “temporarily” disposed to engage in the relevant classification behaviour already concedes too much. If one perceives that X is F only if one is disposed to engage in F-classification behaviour with respect to X, then the point at which one ceases to be so disposed one also ceases to have the perceptual experience in question. However, in the case of a Muller-Lyer illusion, the agent continues to have the perceptual experience of the lines being different lengths even after she is no longer disposed to classify them as such.

Putting aside the above caveat, Dilworth’s treatment of the Muller-Lyer illusion case fails to generalise to that of the partially submerged stick. In the latter the conflict is not between a perceptual experience and a prior belief (as is plausibly the case in the Muller-Lyer illusion), but rather between two conflicting perceptual experiences. In fact, we can imagine a modified partially submerged stick example in which the agent fails to form a belief altogether. We may suppose that, confronted with conflicting perceptual experiences, the agent simply decides to remain agnostic as to whether the stick is straight or bent. (Recall, we have assumed that the agent is unfamiliar with, and therefore has no prior beliefs about, the phenomenon of refraction.) However, even if the agent were to decide to withhold belief altogether, she may still continue to enjoy both sets of conflicting perceptual experiences. Thus, unlike the Muller-Lyer case, the partially submerged stick example presupposes no competing beliefs or knowledge.

It is important to get clear on why this poses a problem for Dilworth’s account. The problem is not that the partially submerged stick case threatens to undermine Dilworth’s claim that any given perceptual experience may be accompanied by a corresponding consonant belief. Since Dilworth wishes to defend the claim that a belief about how things seem to one must be consonant with the corresponding perceptual experience (if one were to form such a belief at all), the mere fact that such a consonant belief is absent (as we may suppose it is in the partially submerged stick case) is no counterexample to the functional consonance thesis. (On at least this much, Dilworth and I agree.) Moreover, I hold that if the agent were to form beliefs about both her visual and tactile experiences, then each respective belief would be consonant with the corresponding perceptual experience. This is something I believe Dilworth would also wish to say; though I maintain that he is not entitled to do so until he has filled in the gap described by Upshot. However, this is not the worry I presently wish to press.

Instead, the present worry has to do with Dilworth’s claim that in any given situation, S, it is logically impossible for an agent to be disposed to engage in mutually exclusive classification behaviours in response to S. Insofar as he is also committed to the claim that an agent perceives that X is F only if that agent is disposed to engage in F-classification behaviour with respect to X, then the partially submerged stick example shows that an agent may be disposed to classify the same object as both bent and straight. Dilworth must therefore either give up the claim that it is logically impossible to have conflicting perceptual dispositions or the claim that being disposed towards classification behaviour (of the relevant kind) is a necessary condition for perception.

Another tempting (but ultimately unsuccessful) response available to Dilworth is to argue that the partially submerged stick example is an instance of a “mixed case”; one “in which several properties are simultaneously perceived, each of which would require its own separate experience versus belief consonance analysis.” The example that Dilworth provides is that of perceiving an object as being a certain colour (with one sensory modality) and perceiving it as having a certain shape (with another sensory modality). Regarding such mixed cases Dilworth maintains there cannot be any conflict:

Now arguably mixed cases of simultaneous perception of different properties would always be cases involving properties falling under different determinable, since one could not simultaneously perceive an object both to have determinate colour F1 and also to have a distinct determinate colour F2.

The above observations may be perfectly correct as far as they go, but they fail to address the issue at hand. Recall, the objection with which this post is concerned is not directed against the notion of experience/belief consonance per se (to which I am sympathetic), but against the conjunction of the claims that (a) it is logically impossible to have two conflicting dispositions and (b) that being disposed to engage in classification behaviour is a necessary condition for perceiving that X is F. Dilworth fails to consider cases in which different sensory modalities present an agent with conflicting information with respect to the same property. The partially submerged stick example is one such case; an instance in which both the visual and tactile sensory modalities provide information about an object’s shape. Thus, unlike the mixed cases that he considers, the partially submerged stick example appears to be a genuine instance in which Dilworth is forced to either (a) acknowledge that an agent may be simultaneously disposed to engage in conflicting classification behaviours or (b) give up on the idea that being disposed to engage in the classification behaviour is a necessary condition for perception.