Gill, a heads up: Penfold also thought that "An existing god exists necessarily" was a fairly decent argument for the existence of a god. So don't read too much into it.
If you had read my full post I made the point that NO ontological was valid (in fact I am more than happy to make the broader claim that no proofs of God of any kind are valid). My point was that the use of 'necessary' was a counter to the Gaulino's Island problem; which it is. Not to get too personal, but ad hominem
attacks are better when you actually have taken the time to read the posts of the person you are criticizing...
...how is this a problem with materialism? What it seems to be is a problem with the idea of unconscious factors. It arises as a "problem" for any theory of mind that includes components to the thought-process that the thinker is not consciously aware of. This affects supernaturalism just as well as it does naturalism, only supernaturalism usually gets a pass in practice because it is not expected to form coherent explanations in the first place.
I am not arguing for super-naturalism at all. My point is that materialism fails to provide a good account of the fact/value distinction.
A materialist account of a belief will take the following form: Some material precursors cause
a certain brain state which correlates to a belief. This is fine, and to my mind probably true. The experiment I quoted in the post above provides us with good evidence for this account.
We can know two things about this materialist account of belief; (a) it will be causal (b) it will be descriptive.
However if we ask a person why they believe something, they will give us reasons
. This account will not be (a) rational and (b) evaluative. ie "I believe so and so for the following good reasons
Materialism cannot provide us with evaluative
accounts only descriptive
ones (this is obvious as no scientific account can admit of value - cf Popper, Kant, Hume etc...).
Let us take the example of a student's belief in Pythagoras' Theorem. If we asked her why she believes it we would expect her answer to take the form of reasons such as: “because of the following mathematical proof”; “because I have been taught it by my teacher”; “because when I apply it in the context of an exam it is marked as correct” etc... If we were to then ask her how important each factor was we would expect an intelligible answer; most likely elevating the mathematical proof over and above the other reasons.
The material description, on the other hand cannot determine what a 'good reason' for a belief is. From the causal story the student's belief in Pythagoras has as much to do with her attending school on a certain day as the validity of any mathematical proof.
So let us take belief in materialism. That is caused in exactly the same kind of manner as a belief in God, in that both are caused by particular material antecedents. To say (as we would want to) that materialism is a good belief and God is a bad belief, we require a theory of reasons
which in turn requires an evaluative
None of this is controversial, all Gill and I have done is talk about a well known problem of philosophy. Dan Dennet (the most important materialist philosopher working today), spend the whole of the second chapter of Elbow Room
trying to give a materialist account of reasons - materialist philosophers are well aware of the problem. I personally think his account is seriously lacking. I am happy to discuss his approach but not here, its not my OP.
Hope that helps