One really interesting answer to this question comes from Wittgenstein, who proposes a form of what has since been called ‘behaviourism.’ Wittgenstein’s philosophical behaviourism holds that ‘I believe X’ means ‘I am disposed to behave in a certain way given certain conditions’; and nothing more. All ‘a belief’ means is 'a tendency to do and say certain things given certain circumstances'. For example, if I believe that it is raining, all this means is that I display rain-like behaviour, such as putting up an umbrella, groaning about how I’m getting wet, etc. On this view, ‘belief’ is reduced radically to external, observable behaviour such as actions and sounds; ‘belief’ does not refer to anything going on inside my head, not even to a physical brain state or collection of brain processes. All it is to believe something (Wittgenstein and other behaviorists taught) is to be disposed to act in a certain way under certain conditions.
Why should we believe that this radical, externalist treatment of folk psychology is correct? Wittgenstein presented an interesting argument to show why: what has now been termed the ‘beetle in a box’ argument. In 'Philosophical Investigations', Wittgenstein imagines three people, each with a box in front of them that only they can look into (they can’t look into each others’ boxes). Each person looks into his/her box, and announces that inside their box, there is a ‘beetle.’ Wittgenstein points out that although the same word is being used to denote the contents of each box, there is no reason at all to think that each box contains the same object. The first person’s box could contain what we mean by beetle; the second person’s box could contain a fish; the third person’s box could contain nothing at all. We cannot know what is in each box, Wittgenstein points out, by merely listening to the word that each person uses to describe the contents of his/her box. Therefore, the word ‘beetle’ is meaningless when given meaning by a single person, and tells us nothing of what is within.
Wittgenstein’s main point is to show that all language is essentially public. There can be no such thing as a private language, because meaning is determined by public use, and in the beetle case, each person is employing his/her own unique use of ‘beetle.’ So too with words such as ‘belief’, ‘desire’, etc: using them to refer to private, intangible events going on inside peoples’ heads is meaningless, since the beliefs in your head are like a private language, only accessible to you, and nobody else. However, we know that ‘belief’ is a meaningful term; so, it must refer to something external and publicly verifiable: a behavioural disposition. (Whether Wittgenstein was a 'behaviourist' in a full sense is controversial, but we can take his reasoning here to provide a clear argument for behaviourism).This conception of mental states such as belief is both very appealing and very counter-intuitive. It is appealing because it demystifies the mental; the mind can be given a much more plausible material explanation if beliefs and desires etc are no longer seen as intangible, ‘spooky’ occurrences inside our heads. However, the view is counter-intuitive because when we believe something, it seems obviously true that this is an inner mental event, something more interesting than a series of external behavioural patterns. Whether we accept Wittgenstein’s argument depends on how seriously we take what seems to go on in our stream of consciousness: how real is the internal nature of the mind? This question is absolutely central to the philosophy of mind, especially in questions about the phenomenon of consciousness, and the problems that arise from it.
