One often hears critics of naturalism say something along the lines of ‘if all we are is the product of chemicals and matter being governed by the impersonal laws of nature, then all our thoughts and ideas are also products of chemical reactions governed by natural laws, and therefore have no meaning.’ This is often followed with ‘why should I listen to you? it’s all just a product of random physical processes!’
Now, if naturalism is true, it doesn’t follow that our faculties are unreliable, at least not in the logical sense. As folks like Plantinga have argued, it is in fact more probable, given naturalism, that our faculties aren’t trustworthy, but it’s not necessary that they be untrustworthy.
Here Alvin Plantinga presents and defends his Evolutionary Argument Against Naturalism with/against Stephen Law, himself not a theist. A fascinating argument and a fascinating discussion well worth your time.
Roughly speaking, the EAAN has its roots in C.S. Lewis’s book ‘Miracles’ where he states that naturalism undercuts its own justification. Plantinga has developed it into a fairly formidable argument.
‘Naturalistic evolution gives its adherents a reason for doubting that our beliefs are mostly true; perhaps they are mostly mistaken; for the very reason for mistrusting our cognitive facultiesgenerally, will be a reason for mistrusting the faculties that produce belief in the goodness of the argument.’
– Alvin Plantinga – taken from http://www.bethinking.org/science-christianity/an-evolutionary-argument-against-naturalism.htm – an outline of a lecture Plantinga gave on the argument. Again, well worth reading. It’s fairly technical but provides good context for the argument.