"brains evolved by natural selection, their main purpose is to cause organisms to behave adaptively in the real world--not to directly represent the real world"

Sounds familiar: The following is from wikipedia (http://en.wikipedia.org/wiki/Evolutionary_argument_against_n...)

“[W]ith me the horrid doubt always arises whether the convictions of man's mind, which has been developed from the mind of the lower animals, are of any value or at all trustworthy. Would any one trust in the convictions of a monkey's mind, if there are any convictions in such a mind?” – Charles Darwin

Alvin Plantinga's evolutionary argument against naturalism began with the observation that our beliefs can only have evolutionary consequences if they affect behaviour. Natural selection does not directly select for true beliefs, but rather for advantageous behaviours. Therefore any belief we hold, being a product of evolution, is as likely right as wrong.

Plantinga distinguished the various theories of mind-body interaction into four jointly exhaustive categories:

1) Epiphenomenalism, where behaviour is not caused by beliefs:
"if this way of thinking is right, beliefs would be invisible to evolution" so the proposition that our faculties are "reliable" would be unsupported.

2) Semantic epiphenomenalism, where beliefs have a causative link to behaviour but not by virtue of their semantic content:
Under this theory, a belief would be some form of long-term neuronal event. However, on this view the proposition that our faculties are "reliable" would be unsupported because the semantic content of beliefs would be invisible to natural selection, and it is semantic content that determines truth-value.

3) Beliefs are causally efficacious with respect to behaviour, but maladaptive, in which case the proposition that our faculties are "reliable" would be unsupported.

4) Beliefs are causally efficacious with respect to behaviour and also adaptive, but they may still be false:
Since behaviour is caused by both belief and desire, and desire can lead to false belief, natural selection would have no reason for selecting true but non-adaptive beliefs over false but adaptive beliefs. Thus the proposition that our faculties are "reliable" in this case would also be unsupported. Plantinga pointed out that innumerable belief-desire pairs could account for a given behaviour; for example, that of a prehistoric hominid fleeing a tiger:

Perhaps Prehistoric Paul very much likes the idea of being eaten, but when he sees a tiger, always runs off looking for a better prospect, because he thinks it unlikely the tiger he sees will eat him. This will get his body parts in the right place so far as survival is concerned, without involving much by way of true belief. [...] Or perhaps he thinks the tiger is a large, friendly, cuddly pussycat and wants to pet it; but he also believes that the best way to pet it is to run away from it. [...] Clearly there is any number of belief-desire systems that equally fit a given bit of behaviour.

Thus, Plantinga argued, the probability that our minds are reliable under a conjunction of philosophical naturalism and naturalistic evolution is unsupported. Therefore, to assert that naturalistic evolution is true also asserts that one has an insupportability of being right. This, Plantinga argued, epistemically defeats the belief that naturalistic evolution is true and that ascribing truth to naturalism and evolution is internally dubious or inconsistent.