Posted by
D W W Robertson on Tuesday, May 13, 2008 5:49:46 PM
Definitions:
Naturalism = the belief that everything that exists is physical in nature (consequentially, immaterial things like God, souls, spirits, etc. do not exist).
Evolution = the proposition that we originated and evolved according to contemporary evolutionary theory.
Plantinga argues that if naturalism is true and evolution is true, then the probability that our cognitive faculties are reliable is low. This is because evolution rewards ‘survival’ behavior, not accurate beliefs. So, this argument depends largely on the relationship between beliefs and behavior. For example, if you believe that a tiger will eat you (and do not want to be eaten), you will run. But you may also believe that the tiger is playing a game of tag with you (and since you want to win), you will run as a result. There are numerous incorrect beliefs that illicit ‘survival’ behavior for every one correct belief that accurately reflects the actual state of affairs. So, you can see why there is little evolutionary advantage for a species whose cognitive faculties are reliable.
This is especially true for abstract beliefs such as the propositions that God exists, that courage is a virtue, or that our mind and our brains are distinct entities. This of course is also true of the proposition that naturalism is true-it is an abstract concept. If you believe that naturalism is true, then you should also believe that the very cognitive faculties you used to arrive at that belief are unreliable. In other words, if naturalism is true, then we are all stupid. Or as Plantinga states naturalism creates its own defeater; naturalism is self-defeating.
Plantinga explains his argument much more eloquently and in a much more rigorous fashion. I have paraphrased and left out quite a few steps for the sake of summary. You can read Plantinga’s own words here: Naturalism Defeated. I just hope that anyone who reads this takes it seriously.