Karen Neander's summary exposition of Teleological Theories of Mental Content at the Stanford site is a very good introduction to what is, after all, a complex topic. http://plato.stanford.edu/entries/content-teleological/
Regarding teleological explanations generally, I find that, especially when we get to the 'belief' level of explanation (Millikan, Dretske, Price et. al.) that the explanations (which are usually of behaviour) are invariably post hoc; and hindsight is a wonderful thing! Now there's nothing wrong with behavioural analyses per se, but I do not think that they get us close to a real sense of telos. At risk of a poor mixed metaphor, they tell us why the cart follows the horse and nothing about why the horse is going that way in the first place. These 'behaviourist' explanations seem always to be 'back-propagating' in ascribing 'causes' to observed 'effects'. I would be happier with a theory which could accurately predict 'effects' from 'causes', which seems to be a more scientific approach (rather than a social scientific approach).
Apropos this point, Neander puts forward a scenario described by Paul Pietroski (1992), which I’ll quote.
In the beginning, the kimu are simple-minded, color-blind creatures. Then Jack is born with an internal mechanism that produces a certain brain state, B, in response to certain wavelengths of light. Jack enjoys the resulting sensation as do those of his descendants who inherit the mutation and the mechanism. As Pietroski wants to describe the case, B has the content, red. Jack's descendants see red and are attracted to it, which leads them to climb to the top of the nearest hill every morning to see the rising sun. As luck has it, they consequently avoid the dawn-marauding predators, the snorf, who hunt in the valley below, and as a result (and solely as a result of this) there is selection for the mutation. The point of the story is that Millikan's theory does not allow the story to be told this way. On her theory, Jack's descendants do not represent red, and so cannot see red or desire to see it. For it wasn't the mapping between B and red, but between B and snorf-free-space that was most crucial for the fitness of Jack and his descendants. Thus, on Millikan's theory, Bs mean snorf-free-space (or fewer snorfs this way, or something of this sort) and there is no representation of red by the kimu.1
On this point Neander ascribes a certain position to Carolyn Price (2001), which seems to raise problems for the Millikanian approach.
Carolyn Price (2001), who offers a detailed teleological theory that closely follows Millikan's in some respects, also defends Millikan's interpretation of the kimu's representation. She claims that this interpretation does a better job of explaining their behavior by making it seem rational. In doing so, she endorses the idea that the point of making content ascriptions is to rationalize behavior. The thought is that a desire to avoid snorf is a better reason for climbing to the top of the hill than a desire to watch the sun rise is. A number of responses are possible. One is to contend that a desire to watch a sun rise is a good enough reason for climbing to the top of a hill. One might also argue that, while her interpretation explains why the kimu climb to the top of the hill, it provides a peculiar explanation of why the kimu crowd into snorf-infested spaces when the snorf are near red: i.e., on this interpretation, the kimu reliably mistake snorf-infested spaces that are near red for snorf-free spaces. Which interpretation best rationalizes the behavior can therefore be disputed. A different response is to question whether it is the role of content ascriptions to rationalize behavior. 2
The question is, do teleological theories of meaning content offer a sufficiently rigorous explicatory framework?
1. Neander, K. Stanford Encyclopedia of Philosophy http://plato.stanford.edu/entries/content-teleological/
Pietroski, P., 1992, "Intentional and Teleological Error", in Pacific Philosophical Quarterly, 73: 267-81.
Price, C., 2001, Functions in Mind: A Theory of Intentional Content,
Image: ‘The Wood for the Tress’ © Tom Tomos 2010