Hasker on externalism on ham-fisted empiricism
A final escape route for the physicalism might be the adoption of a thoroughly externalist view of justification. What determines the justification of a belief, on this view, is not internal cognitive processes such as were described above, but rather one simple question: was the belief produced by a a reliable belief-forming process? If it was, then no further questions about justification--those asked by the Argument from Reason--need be asked.
It is of course true that a belief, in order to be justified, needs to have been formed and sustained by a reliable epistemic practice. But in the case of rational inference, what is this practice supposed to be? The reader is referred, once again, to the description of a reasoning process given a few paragraphs back. Is this not, in fact, a reasonably accurate description of rational inference and assessment? It is, furthermore, a description which enables us to understand why in may cases the practice is highly reliable--and why the reliability varies considerably depending on the specific character of the inference drawn and also on the logical capacities of the epistemic subject. And, on the other hand, isn't it a severe distortion of our actual process of reasoning as taking place in a "black box," as the externalist view in effect invites us to do? Epistemological externalism has its greatest plausibility in cases where the warrant of our beliefs depends crucially on matters not accessible to reflection--for instance, on the proper functioning of our sensory capacities. Rational inference, in contrast, is the paradigmatic example of a situation in which the factors relevant to warrant are accessible to reflection; for this reason, examples based on rational insight have always formed the prime examples for internalist epistemologies.
There is also the question for the thoroughgoing externalist: How are we supposed to satisfy ourselves as to which of our inferential processes are reliable? By hypothesis, we are precluded from appealing to rational insight to validate our conclusions about this. One might say we have learned to distinguish good reasoning from bad by noticing that good inference-patterns give rise to true conclusions, while bad inference-patterns give rise to falsehood....But this sort of "logical empiricism" is at best a very crude method for assessing the goodness of arguments. There are plenty of invalid arguments with true conclusions, and plenty of valid arguments with false conclusions. There are even good inductive arguments with all true premises in which the conclusions are false. These are just the sort of distinctions which the science of logic exists to help us with; basing this science o n the kind of ham-fisted empiricism described above is a hopeless enterprise.
William Hasker The Emergent Self (Cornell, 1999) pp. 73-5