The Evolutionary Argument Against Naturalism: Simplified and Refuted
Here is the basic argument Plantinga offers. C and ~C are mutually exclusive and jointly exhaustive propositions.
C = The content of our beliefs enters into the causal chain that leads to behavior
~C = The content of our beliefs is epiphenomenal to our behavior
Givin this, what is the probability that our cognitive system is reliable, given Evolutionary Theory and Naturalism: P(R/N & E)? Well, first, the following equality holds:
P(R/N & E) = P(R/N & E & C) X P(C/N & E) + P(R/N & E & ~C) X P(~C/N & E) [I hope this formula makes sense to everyone. If not, ask me to explain it].
Therefore, the probability of R given N & E will be the weighted average. Plantinga conceeds that giving a precise numerical value to each is absurd. All we can hope for is a general estimation. The following are rough estimations that Plantinga would agree with
P(R/N & E & C) = 9/10. This seems right. If the content of our noetic structure (jargon for the belief structure) enters into causal relations with our behavior, then R would have a high probability; for it would be correct to say that our mind accurately represents the world.
P(C/N & E) = 1/10. This will be explained later. In fact, this is what I will be arguing against.
P(R/N & E & ~C) = 1/10. This seems right, atleast prima facia. If the content of our beliefs do not causally influence our behavior, then there would be no reason to think that our minds are reliable. I will also argue that the probability is off on this one too.
P(~C/N & E) = 9/10. I will argue against this too.
So, lets work it out now:
P(R/N & E) = 9/10 X 1/10 + 9/10 X 1/10 = 18/40 = .45
Therefore, you have less than a 50% chance that your cognitive faculties are reliable. I will let you mull this over for awhile before I offer my three tiered critique.
"In the high school halls, in the shopping malls, conform or be cast out" ~ Rush, from Subdivisions