The argument that the wideness of beliefs undermines the representational theory of thinking assumes the truth of this principle. that psychology must explain human behaviour solely in terms of properties which are grounded in physical states of the brain.
the 'theory' it is alleged we ordinarily apply when we explain what people do in terms of their beliefs and desires
This theory assumes a von Neumann type computer model of the brain, so to argue that the brain is not a computer of this type attacks this theory of thinking.
This is the thesis that explaining our own and others' behaviour in terms of beliefs and desires - folk psychology - is completely mistaken and that the advance of neuroscience will clarify what concepts we should employ instead (to give us better predictions). Folk psychology it is claimed throws little or no light on many features of human behaviour. It will be replaced by neuroscience just as Aristotelian physics gave way to Newtonian (which has of course itself given way since).
It is argued that beliefs (which form a central part of Folk Psychology) are made what they are partly by the context of the believer. Putnam argued the same point with his water / twater scenario.
Maybe the brain is not a serial (von Neumann) computer, but a computer of a different type - a connectionist net, or network of connectionist nets.
Updated 26:03:03
VP
According to the computer/brain analogy, what is thinking? The repesentational theory of thought is one answer: what is going on when a person is thinking is that states of bits of the brain represent propositions and these are manipulated in various ways.
By undermining Folk Psychology, the point gives support to eliminativism.