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What is Disjunctivism?

Adrian Haddock tells us about one of the most talked-about new approaches in philosophy today.

I am writing these words in the reading room of the National Library of Scotland. There is a man in front of me chewing the end of his pencil. How I do know this? Why, because I see him in front of me, chewing the end of his pencil.

What is going on here? Well, I think there is a man in front of me chewing the end of his pencil, and my visual experience supplies me with a reason for thinking this – namely, that I see a man in front of me chewing the end of his pencil. This is a truly excellent reason for thinking this. If I see a man in front of me chewing the end of his pencil then there is a man in front of me doing so. Consequently, because I think this for this very good reason, I do not merely think it, but know that there is a man in front of me chewing the end of his pencil.

These are seemingly natural thoughts. But some philosophers believe themselves to be in possession of an argument which shows that they must be rejected. This has come to be known as the Argument from Hallucination. It is possible for me to have an experience ‘just like’ the experience I have of a man in front of me chewing his pencil even when there is no man in front of me chewing his pencil; I could be dreaming of a pencil-chewing man, or having a hallucination of such a man. In that case I could not see a man in front of me doing that, because there is no man in front of me doing that. So in a case like this, I could not have the fact that I see a man in front of me chewing his pencil as my reason for thinking that there is a man in front of me doing that.

Here we have two cases: a ‘good’ case and a ‘bad’ case. In the good case, I see a man in front of me chewing the end of his pencil. In the bad case, I have a dream/hallucination of a man in front of me chewing the end of his pencil. The experience I have in the good case is ‘just like’ the experience I have in the bad case. According to the Argument from Hallucination, it follows that the reasons my experience supplies me with in the good case must be the same as the reasons my experience supplies me with in the bad case. That I see a man in front of me chewing his pencil is not a reason which my experience supplies me with in the bad case, because in the bad case I do not see a man in front of me doing that; so, according to the Argument from Hallucination, this is not a reason which my experience supplies me with in the good case either. The only reasons which my experience supplies me with are those which are neutral between the good case and the bad case. (For example, my experience might supply me with a reason consisting in the fact that I seem to see a man in front of me chewing his pencil.) Therefore, the seemingly natural thoughts with which we began must be given up.

Two Sorts of Disjunctivism

In 1982 the philosopher John McDowell gave a lecture (published in 1983 as ‘Criteria, Defeasibility, and Knowledge’) which sought to rescue our seemingly natural thoughts from the Argument from Hallucination. McDowell pointed out that it does not follow from the fact that my experience in the good case is ‘just like’ my experience in the dream/hallucination case, that the reasons my experience supplies me with must be the same in both cases. Why not say instead that, even if my experience in the good case is ‘just like’ my experience in the bad case, it can still supply me with a reason which my experience in the bad case cannot supply me with – a reason consisting in the fact that I see a man in front of me chewing his pencil? (The Argument from Hallucination does not tell us why we cannot say this. It simply assumes, without argument, that we cannot say it.) Put differently, why not say that my experience either supplies me with one sort of reason (i.e. that I see how things are) or supplies me with a different sort of reason (i.e. that I seem to see how things are)? McDowell originally expressed this suggestion in the guise of a disjunction – a statement of the form ‘either this or that’. This is one reason why his suggestion has acquired the unappealing name ‘disjunctivism’: a name which led Simon Blackburn waggishly to describe its advocates as suffering from ‘disjunctivitis’. (I suspect another reason has to do with contemporary philosophy’s ‘ism-itis’.)

Since McDowell’s lecture, interest in disjunctivism has not merely grown but spiralled – if not out of control, at least in several different directions. One way to summarise McDowell’s position would be to say that even though the experience in the good case is ‘just like’ the experience in the bad case, there is a fundamental difference between the experiences in terms of the reasons they supply me with. This idea of a fundamental difference between experiences which are ‘just like’ one another is also central to recent writings on disjunctivism – best represented perhaps by Mike Martin’s paper ‘The Transparency of Experience’ in Mind and Language, vol. 17 (2002). However, McDowell’s concern with experience’s capacity to supply us with reasons is discarded by these recent writings, in favour of a quite different understanding of the fundamental difference between two experiences ‘just like’ one another.

According to one variant of the Argument from Hallucination, it follows from the fact that my experience in the good case is ‘just like’ my experience in the bad case that the components of my experience must be the same in the two cases. In the bad case, my experience does not have what I see – a man in front of me chewing on his pencil – as a component, because in the bad case I do not see a man in front of me doing that, I only seem to do so. So, according to the Argument, in the good case my experience does not have what I see as a component either. But the variant of disjunctivism which currently dominates discussion of the topic insists that, on the contrary, my good-case experience and my bad-case experience have different components, even though they are ‘just like’ one another. So the fundamental difference between the two experiences is now understood in terms of the experiences’ components rather than in terms of the different reasons the experiences supply me with. This variant on disjunctivism insists that my experience either has what I see as a component, or it does not. Because of its concern with the nature of the experiences, ie, with their components, this variant has come to be known as metaphysical disjunctivism. By contrast. because of its concern with experience as a source of reasons and knowledge, McDowell’s view has come to be known as epistemological disjunctivism. (Alex Byrne and Heather Logue are responsible for these labels: see their ‘Either/Or’ in Adrian Haddock and Fiona Macpherson (eds) Disjunctivism: Perception, Action, Knowledge, 2008).)

Despite the apparent similarities between these two positions, they are quite distinct. One can suffer from epistemological disjunctivitis without suffering from metaphysical disjunctivitis, and vice versa. So we must not assume that to criticise either position it is either sufficient or necessary to criticise the other. The best critical strategy is to treat each position separately, at least in the first instance. So let’s do that.

Metaphysical Disjunctivism

Metaphysical disjunctivism inspires a number of worries. Here is perhaps the most obvious: to say that my experience in the good case is ‘just like’ my experience in the bad case seems to say that they have the same phenomenology. What exactly this means is hard to pin down; but one standard way to gloss it is to say that how things seem from my point of view is the same in the good case as it is in the bad case. However, it also seems that if the components of the former experience are distinct from the components of the latter experience, as metaphysical disjunctivism says, then the phenomenology of the former must be distinct from the phenomenology of the latter. So in claiming that the components of my experiences are distinct, metaphysical disjunctivism makes it seem as though my experiences must differ in their phenomenology – as though how things seem from my point of view in the good case is not the same as how things seem from my point of view in the bad case. This would mean that in some (as yet unspecified) way the experiences are not ‘just like’ each other.

There are some metaphysical disjunctivists who are happy to embrace the conclusion that the phenomenology of my good-case experience is not the same as the phenomenology of my bad-case experience. Mike Martin is the prominent example. However, the metaphysical disjunctivist acknowledges that my experiences are ‘just like’ one another in some sense – namely, in the sense that it is not possible for me to know by introspection alone which experience I am having: whether I see a man in front of me chewing on his pencil, or whether I am having a hallucination of such a man.

What exactly it means to say that something can or cannot be known ‘by introspection alone’ is also hard to pin down; but it is often assumed that introspection is infallible – that if I can know something by introspection alone then I cannot be wrong about it. (I can be wrong about whether I am seeing something, as opposed to hallucinating it; so, I cannot know by introspection alone whether I am seeing or hallucinating it.) So, according to the metaphysical disjunctivist, even though I cannot know by introspection alone whether I am in the good case or the bad case, how things seem from my point of view in the good case is not the same as how things seem from my point of view in the bad case.

This is a difficult and challenging claim, not least because it is not clear that it is fully intelligible. It seems that the difference between two experiences which differ in their phenomenology surely must be knowable by introspection alone: if not, what does it mean to say that the experiences differ in their phenomenology? (That is not to criticize this claim, but to take it seriously. It is often claims which teeter on the bounds of sense that have the strongest claim to fire the imagination of philosophy.)

Epistemological Disjunctivism

Epistemological disjunctivism does not face this question, but it does face questions and worries of its own. It claims that I can know that there is a man in front of me chewing his pencil because I have a reason to think that there is – namely, that I see the man in front of me, chewing away. But surely I cannot know this because I have this reason unless I can also know that I have this reason – unless I can also know that I see a man in front of me chewing on his pencil? And how can I know that I have this reason if I cannot know by introspection alone whether I am seeing a man chewing as opposed to having a hallucination of him?

The epistemological disjunctivist has various ways of responding to these questions. She might try to show that I can know by introspection alone whether I am seeing a man as opposed to having a hallucination of him. Or she might try to deny that I need to know that I have the reason in virtue of which I know that there is a man in front of me chewing on his pencil. But it might be best for her to insist that even if I cannot know by introspection alone whether I am seeing the man, I can still know whether I am seeing him; we must not assume that if this is not knowable by introspection alone then it is not knowable at all. But then, the question for the epistemological disjunctivist is, how do I know whether I’m seeing him? This is another large question, but it is not clear that it cannot be satisfactorily answered. I sketch an answer in my contribution to The Nature and Value of Knowledge: Three Investigations by Duncan Pritchard, Alan Millar and Adrian Haddock (OUP, 2010).

Disjunctivism is an important topic in contemporary philosophy, bearing on deep and difficult questions about the nature of experience, knowledge, reasons, introspection and phenomenology. However, if I am right then disjunctivism is properly understood as two topics: metaphysical and epistemological. Most contemporary discussions centre on its metaphysical variant, but I hope that philosophers will be persuaded to pay as much attention to epistemological disjunctivism as they are currently paying to its metaphysical second cousin, twice removed.

Adrian Haddock is a Lecturer in the Philosophy Department at the University of Stirling.