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.
It is argued that there are reasons for rejecting the Churchlands' view and for insisting that thinking must be quasi-linguistic. Fodor's 'Why there has to be a language of thought' is the central paper here.
Any theory of thinking has to account for the fact that thoughts seem to 'point' - possess intentionality.
What is intentionality? How can we envisage physical systems such as computers (or bits of them) acquiring it?
Besides thoughts, language items (eg sentences) seem to have intentionality.
What is the connection between the fact that language items have intentionality and the fact that thoughts have intentionality? - The thesis that it is thinking that confers intentionality on language items (eg by uttering them with something in mind).
The idea that physical systems like brains (or bits of them) acquire intentionality through their sense experience, and/or through evolution.
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
There is another theory, which is the one sketched by the Churchlands in 'Stalking the Wild Epistemic Engine'. They argue that there a good deal of 'thinking' which cannot plausibly be thought of as involving representations of propositions. They think it involves representations but not representations of propositions.