Ned Block on Disjunctivism

In the last few days I had the good fortune to attend a couple of talks here at Warwick by Ned Block. In the first of these, which I discuss below, Block set about attacking the disjunctivist conception of experience put forward by (amongst others) Mike Martin, Alva Noë and Susan Hurley. On this object-involving view of experience, not only semantic content but also the phenomenal character of experience itself is said to be externally individuated—a view which Block has argued against elsewhere, and which is defended by Michael Tye. This goes beyond the widely accepted arguments put forward by Putnam, Burge, et al., and results in a view upon which the felt qualities of experience are partly (although not necessarily wholly) constituted by external objects.

Block confessed from the outset that he was relatively ignorant of the literature on disjunctivism, which is admittedly sprawling and difficult to interpret. For those who have not come across the term, disjunctivism is, to put it crudely, the view that experience or mental state types should not be individuated on the basis of their phenomenal character—i.e. ‘what it’s like’ for the subject—but also on the basis of external properties, such as their epistemic status. Thus, a veridical perceptual episode and a hallucination would be taken to be two different types of experience whose only common factor is that they are phenomenally indistinguishable from one another, and where this need not be taken to indicate any other common factor at the level of the mental.

In general, Block’s strategy was to argue from the existence of cases in which we have empirical evidence for the internal individuation of mental states to the implausibility of external individuation in general. In particular, he wished to attack a particular claim by Martin to the effect that the relevant externally individuated states (e.g. perception and hallucination) have ‘no positive mental characteristics in common’ apart from the fact that they are phenomenologically indistinguishable (something that all sides accept is possible in theory, if not necessarily in practice). Block took this to mean that the disjunctivist is committed to denying that, for example, a seen rose can be exactly the same shade of red as an imagined post box on the basis that ‘being the same shade of red’ is a positive mental characteristic. However, as was pointed out in questions afterwards, it is not clear that this is at all inconsistent with Martin’s claim. Indeed, one might think that such such equivalences are entailed by precisely the notion of phenomenological indistinguishability that the disjunctivist posits, and so do not constitute any additional mental characteristics over and above this notion. Conversely, if this is not what disjunctivism entails, then it is trivially false, not to mention inconsistent, and so this cannot be the correct reading of Martin’s claim.

A further difficulty with Block’s approach was that he took the idea that experience types are individuated by anything other than their subjective phenomenal character (i.e. ‘what it’s like’) to be manifestly false. The problem is—and this was news to him—that this is precisely what the disjunctivist is claiming, and so cannot be taken as a problem for the view per se. If there is something inherently problematic about this notion, then Block failed to show what it was, despite a fascinating discussion of several interesting case studies within the neuroscientific literature.

Furthermore, it was unclear (to me at least) why such examples should constitute a counterexample to disjunctivism. Block’s argument seemed to be that the physical states that differentiate one phenomenal character from another lie in the core regions of the brain, and not in the retina or early visual system. By extension, this means that they cannot lie in external objects, and so (Block claims) phenomenal consciousness must be purely internal. However, this argument says nothing about how experience types or mental states should be individuated or how they are realised in phenomenologically indistinguishable but functionally distinct states; e.g. dreaming. Even if such states did turn out to have a common physical basis, however, this does not appear to be inconsistent with the disjunctivist claim that they have nothing in common (with the exception of phenomenological indistinguishability) at the level of the mental. Consequently, seeing an apple and dreaming that you see one do not necessarily constitute the same mental state.

Another argument against externalism about phenomenal consciousness that was not fully spelled out, and in my view was weaker than the above, traded on the idea that we are able to ‘mesh’ visual and imaginary experiences with relative ease. In the case of two grid of dots being projected onto a screen in succession, for example, subjects are able to locate the missing dot—i.e. the one that didn’t appear in either presentation—despite the fact that one image is perceived and the other only remembered or imagined (although it is not clear that the sort of memory involved is not itself perceptual in nature). However, this only shows that such experiences have a common content—something that both sides admit—and not that they are necessarily of the same type, or are comprised of the same mental state.

Putting the above worries—which in my view are fatal to Block’s argument—to one side, it was still an extremely enjoyable and interesting talk. There was even a nice demonstration of the phenomenon of binocular rivalry in which different images are presented to the left and right eyes, causing a kind of visual flip-flopping effect, for which pairs of 3D glasses were distributed. Indeed, the spectacle (excuse the pun) of Warwick’s finest philosophers peering at a screen whilst wearing 3D glasses was worth going to the talk for in its own right. At one point Block described Warwick as a “hotbed of disjunctivism”, which caused a few chuckles, although is perhaps something of an overstatement given that relatively few of the Warwick faculty ‘self-identify’—since when did this phrase become part of the philosphical lexicon?—as disjunctivists.

In general, however, I remained unconvinced by the evidence that Block presented, most of which seemed (so far as I could tell) to cut against his own interpretation of the disjunctivist’s position, rather than disjunctivism proper. Indeed, as Block at one point came close to admitting, once these misunderstandings are cleared up then the central thesis of disjunctivism doesn’t seem that contentious after all, and in fact turns out to be rather uninteresting from a scientific point of view due to its lack of distinctive empirical claims. It is, after all, a philosophical thesis, rather than an empirical one. The broader philosophical—and in particular epistemological—benefits of the theory, however, remain a matter of intense debate—not least because the precise commitments of the view itself are often poorly articulated and/or understood.

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