The unity of hallucinations

Authors: Fabian Dorsch

Publish Date: 2010/05/05

Volume: 9, Issue: 2, Pages: 171-191

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Abstract

My primary aim in this article is to provide a philosophical account of the unity of hallucinations which can capture both perceptual hallucinations which are subjectively indistinguishable from perceptions and nonperceptual hallucinations all others Besides I also mean to clarify further the division of labour and the nature of the collaboration between philosophy and the cognitive sciences Assuming that the epistemic conception of hallucinations put forward by M G F Martin and others is largely on the right track I will focus on two main tasks a to provide a satisfactory phenomenology of the subjective character of perceptions and perceptual hallucinations and b to redress the philosophers’ neglect of nonperceptual hallucinations More specifically I intend to apply one of the central tenets of the epistemic conception—that hallucinations can and should be positively characterised in terms of their phenomenological connections to perceptions—to nonperceptual hallucinations as well That is I will try to show that we can positively specify the class of nonperceptual hallucinations by reference to the distinctive ways in which we firstpersonally experience them and perceptions in consciousness The task of saying more about their underlying thirdpersonal nature may then be left to the cognitive sciencesIt is common both in philosophy and in the cognitive sciences broadly understood as ranging from say neuroscience to developmental or evolutionary psychology to distinguish between two kinds of hallucinations1 What differentiates them is whether they are subjectively indistinguishable from genuine perceptions and therefore mistaken by us for the latter While perceptual or ‘true’ hallucinations cannot from the subject’s perspective be told apart from perceptions nonperceptual or ‘pseudo’ hallucinations can and usually are Sometimes when subjects say auditorily hallucinate someone else calling their name or commenting on their behaviour they are able to realise on the basis of how they subjectively experience their episode of hallucination that they are not perceiving real speech their hallucination is nonperceptual This happens for instance when subjects suffering from schizophrenia or other illnesses hear ‘inner voices’ speaking to them but in other circumstances the subjects concerned are—even under conditions of proper mental health and rationality—in no position to recognise the hallucinatory status of their experience without the help of some external evidence their hallucination is perceptual Wrongly hearing the phone ringing while taking a shower say is a good example of this kind of hallucination2When philosophers speak or write about hallucinations they usually concentrate on perceptual hallucinations One reason for this is the fact that philosophers tend to address the topic of hallucination not for its own sake but only in the context of some wider issues Thus when they are discussing hallucinations they are primarily interested in other topics such as how—or whether—we are able to acquire knowledge about the external world in which sense our mental states are directed at objects and properties how best to account for what our experiences are subjectively like and which features suffice for something to count as a conscious experience Especially the epistemic question but also the connected issues in the philosophy of mind leads them first of all to the phenomenon of genuine perception for perceptions are precisely those mental episodes which point us to and bring us into contact with the world and they also constitute the paradigm examples of conscious episodes with a distinctive phenomenal character Hallucinations on the other hand do neither Instead they become relevant for the epistemic and related considerations only insofar as they give rise to sceptical scenarios and cast doubt on the common sense or naive conception of the nature of perceptual experiences and in both cases only those hallucinations matter which are indistinguishable from genuine perceptions with respect to their content and character3In the cognitive sciences by contrast hallucinations are much more prominent objects of study and moreover objects of study in their own right From the perspective of empirical investigations of the brain and mind—whether they utilise neuroimaging observe behaviour or examine verbal reports—hallucinations simply form one class of mental phenomena among many In addition all these phenomena are ultimately in the same need of being scientifically studied and accounted for as part of our attempt to come to a full understanding of how our psychology works and is neurally realised Of course scientists too are interested in learning how we manage to cognise reality or why consciousness arises in the way that it does and this may as well focus some of their research more on perceptions and perceptual hallucinations than on nonperceptual hallucinations However scientists are equally interested in coming to understand—and to enable the people concerned to cope with—the errors abnormalities and pathologies of our mental lives to which all types of hallucination belong as different deviations from the norm of genuine perception The study of hallucinations does not only help us to better grasp how perception normally functions It also makes an independent contribution to a comprehensive picture of our minds especially with respect to the psychologically more problematic or puzzling aspects of our mental lives It is part of this that nonperceptual hallucinations are as much at the centre of scientific inquiry as are their perceptual counterparts4This raises the issue of the division of labour between philosophy and the cognitive sciences what are their specific roles in the investigation of the nature and features of hallucinations However it also leads to the question of what unifies the two broad kinds of hallucinations why do we classify them both as hallucinations and distinguish them from other mental phenomena such as perceptions imaginings or memories This latter issue is especially pressing because of a simple fact about our cognition of the world When we are trying to get into contact with reality there is only one way of getting it right—namely perception However there are many ways in which our minds may fail to establish any such perceptual relation to the world5 Hence it cannot simply be assumed that all those failures—that is all hallucinations—share a distinctive and unifying feature over and above their lack of a provision of perceptual access to reality and any characterisation in terms of the latter threatens to remain largely negative and therefore not very illuminatingOne promising answer to this challenge which has gained prominence in the recent philosophical debate on perceptual hallucinations and their relevance for a theory of perceptual experiences is the epistemic conception of perceptual hallucinations According to this view nothing more can—or need—be said about perceptual hallucinations than that they are subjectively indistinguishable from perceptions without actually being perceptions6 The epistemic—and phenomenological—element in this conception is the indistinguishability thesis which concerns the phenomenal characters of the two kinds of episode and corresponds to the specification of perceptual hallucinations offered at the beginning It is this element which provides the positive characterisation of perceptual hallucinations missing so far they are precisely those mental episodes which despite not being perceptions seem to share their character with perceptions—they are given to us in consciousness as if they were perceptionsHowever the epistemic conception of perceptual hallucination still leaves a lot of work to be done One reason for this is that it concentrates on the firstpersonal or subjective side of the hallucinations ie their conscious or experiential nature but largely ignores its thirdpersonal or objective side ie their physical or neurofunctional nature This means that even if philosophical theories of perceptual hallucinations are limited to a phenomenological description of our access to the conscious character of these hallucinations their underlying structure below the level of consciousness is still open to discovery by the cognitive sciences This structure includes the various ways in which hallucinations may come to be realised by the brain which psychological abnormalities they are correlated with if any how many different types of hallucinations there are as a result and so on7In addition despite the modest or pessimistic outlook of the epistemic conception there are also important tasks left for philosophy On one hand there is still the need for a satisfactory phenomenology of the subjective character of perceptions and relatedly of the subjectively indistinguishable character of perceptual hallucinations8 The resulting phenomenological descriptions should also be of interest to the cognitive sciences especially if they manage to be more systematic rigorous and detailed than those currently used in cognitive psychology and the related disciplines cf the discussion of the latter in the fourth section On the other hand philosophy needs to reassess its treatment—or rather neglect—of nonperceptual hallucinations The epistemic conception in particular cannot be applied to them since they can be subjectively distinguished from perceptions The existence of nonperceptual hallucinations thus poses a particular challenge to the formulation of a unified philosophical theory of hallucinations—especially of a theory which manages to hold on to the phenomenological insights of the epistemic conception of perceptual hallucinations while also being able to capture nonperceptual hallucinations

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