An argument against naturalism

[downbeatplumb]

Elsewhere, I've been arguing with a theist who was a proponent of C.S. Lewis' Argument from Reason. Here it is:

1) For an assertion to be capable of truth or falsehood it must come from a rational source (see explanation below).
2) No merely physical material or combination of merely physical materials constitute a rational source. (i.e. anti-panpsychism)
3) Therefore, no assertion that is true or false can come from a merely physical source.
4) The assertions of human minds are capable of truth or falsehood
Conclusion: Therefore, human minds are not a merely physical source (see explanation below).

The argument for the existence of God holds:

(5) A being requires a rational process to assess the truth or falsehood of a claim (hereinafter, to be convinced by argument).
(6) Therefore, if humans are able to be convinced by argument, their reasoning processes must have a rational source.
(7) Therefore, considering element two above, if humans are able to be convinced by argument, their reasoning processes must have a non-physical (as well as rational) source.
(8) Rationality cannot arise out of non-rationality. That is, no arrangement of non-rational materials creates a rational thing.
(9) No being that begins to exist can be rational except through reliance, ultimately, on a rational being that did not begin to exist. That is, rationality does not arise spontaneously from out of nothing but only from another rationality.
(10) All humans began to exist at some point in time.
(11) Therefore, if humans are able to be convinced by argument, there must be a necessary and rational being on which their rationality ultimately relies.
Conclusion: This being we call God.

http://en.wikipedia.org/wiki/Argument_from_reason

There's certainly a flaw with it somewhere, and I've got some ideas of my own, but I'd like to know how you'd all counter it.

The flaw is that is just nonsence.

Its similar to the argument about morals coming from the 'ultimate moral being' and is just as fatuous.

My counter argument would be we can rationalise because we are evolved social creatures with problem solving abilities. these are all manifestations of the evoloutionary path our species has taken and down to some elusive sky daddy.