Hallucination: Philosophy and Psychology

8. The Multidisjunctive Conception of Hallucination

8 The Multidisjunctive Conception of Hallucination Benj Hellie Abstract Direct realists think that we can’t get a clear view of the nature of hallucinating a white picket fence: Is it representing a white picket fence? Is it sensing white-picket-fencily? Is it being acquainted with a white′ picketed′ sense-datum? These are all epistemic possibilities for a single hallucination: after all, phenomenological reflection suggests that the nature of that hallucination is being acquainted with a white picket fence; but the suggestion is misleading, and we have no further evidence about this nature. But if these are all epistemic possibilities for a single hallucination, they are all metaphysical possibilities for the hallucinations that subjectively match it. Hallucination of a white picket fence itself is therefore a disjunctive or “multidisjunctive” category. While this undermines M. G. F. Martin’s widely discussed variant of the “causal argument from hallucination” for his epistemic conception of hallucination, Martin’s epistemic category still serves as a reference fixer for my many disjuncts. If one wishes to endorse a direct realist view of perception, in which in a case of seeing, seen objects or their particular features are somehow parts of the experience one undergoes, what other doctrines must one endorse? Michael G. F. Martin has modified the classic “causal argument from hallucination” to support the claim that direct realists must endorse the doctrine that “for certain visual experiences as of a white picket fence, namely causally matching hallucinations, there is no more to the phenomenal character of such experiences than that of being indiscriminable from corresponding visual perceptions of a white picket fence as what it is” (Martin, 2006, 369); this doctrine has lately gone under the name “the epistemic conception of hallucination” or, as I prefer, “epistemic disjunctivism.” The epistemic disjunctivist’s prediction that hallucinations lack an “independent nature” has, in turn, come under assault from a number of directions (Siegel, 2004, 2008; Hawthorne & Kovakovich, 2006; Sturgeon, 2008). Accordingly, both advocates and opponents of direct realism have reason to wonder whether Martin’s causal argument from direct realism to epistemic disjunctivism is successful. 150 B. Hellie This chapter aims to promote, as a direct-realism-friendly alternative to epistemic disjunctivism, the doctrine of “multidisjunctivism”: the view, roughly, that the phenomenal character of this hallucination of an apple consists in acquaintance with a sense-datum of a certain sort, while the phenomenal character of that indiscriminable hallucination of an apple consists in the representation of a certain apple-relevant proposition. (To foreshadow, multidisjunctivism stands to epistemic disjunctivism roughly as “reference-fixing” functionalism stands to “sense-giving” functionalism.) By granting hallucinations an “independent nature,” multidisjunctivism frees direct realism from many of the anxieties provoked by epistemic disjunctivism. To promote the multidisjunctive view, I work toward a negative aim and a positive aim. The negative aim is to rebut a central plank of Martin’s causal argument. The plank in question appeals to a probabilistic relation among properties known as “screening off,” which I will explain later. Considered abstractly, the causal argument begins with the claim that (for certain groups of properties) these properties screen off those properties from these third properties; advances to a certain claim about the causal relations among instances of those properties; and then draws out epistemic disjunctivism as a consequence of this claim about causal relations. My central contention is that the case for epistemic disjunctivism breaks down because the screening-off relation fails to hold in the case at issue. As we will see, the reason for this failure is that the screening-off relation does not hold if multidisjunctivism is coherent; but multidisjunctivism is coherent. This brings us to the paper’s positive aim, which is to argue that multidisjunctivism is not only coherent but also more plausible than its direct realist competitors: it is superior not only to Martin’s epistemic disjunctivism but also to older positions such as those that Byrne and Logue (2008) have labeled “positive disjunctivism” and “the moderate view.” Roughly and briefly, the reason for this is that multidisjunctivism alone respects the link between epistemic and metaphysical possibility, in light of the irremediable uncertainty about the nature of a hallucination that is at the core of direct realism. Accordingly, philosophers friendly toward direct realism need not worry themselves over the status of epistemic disjunctivism: they can and should endorse multidisjunctivism instead.1 In doing so, they would accept both (against Martin) that a hallucination has an independent nature and (with Martin) that there...