  Thinking very much in causal terms about beliefs and desires fits in very well not only with folk psychology but also with Humean ideas about the motives of action. Though this point of view has been criticised by some philosophers it does seem to be right, as can be seen if we consider a possible robot aeroplane designed to find its way from Melbourne to Sydney. The designer would have to include an electronic version of something like a map of south-eastern Australia. This would provide the ‘belief’ side. One would also have to program in an electronic equivalent of ‘go to Sydney’. This program would provide the ‘desire’ side. If wind and weather pushed the aeroplane off course then negative feedback would push the aeroplane back on to the right course for Sydney. The existence of purposive mechanisms has at last (I hope) shown to philosophers that there is nothing mysterious about teleology. Nor are there any great semantic problems over intentionality (with a ‘t’). Consider the sentence ‘Joe desires a unicorn’. This is not like ‘Joe kicks a football’. For Joe to kick a football there must be a football to be kicked, but there are no unicorns. However we can say ‘Joe desires-true of himself "possesses a unicorn" ’. Or more generally ‘Joe believes-true S’ or ‘Joe desires-true S’ where S is an appropriate sentence (Quine 1960, pp. 206–16). Of course if one does not want to relativise to a language one needs to insert ‘or some samesayer of S’ or use the word ‘proposition’, and this involves the notion of proposition or intertranslatability. Even if one does not accept Quine's notion of indeterminacy of translation, there is still fuzziness in the notions of ‘belief’ and ‘desire’ arising from the fuzziness of ‘analyticity’ and ‘synonymy’. The identity theorist could say that on any occasion this fuzziness is matched by the fuzziness of the brain state that constitutes the belief or desire. Just how many interconnections are involved in a belief or desire? On a holistic account such as Lewis's one need not suppose that individuation of beliefs and desires is precise, even though good enough for folk psychology and Humean metaethics. Thus the way in which the brain represents the world might not be like a language. The representation might be like a map. A map relates every feature on it to every other feature. Nevertheless maps contain a finite amount of information. They have not infinitely many parts, still less continuum many. We can think of beliefs as expressing the different bits of information that could be extracted from the map. Thinking in this way beliefs would correspond near enough to the individualist beliefs characteristic of folk and Humean psychology.