"In fact, if evolution were true, there wouldn’t be any rational reason to believe it!"
The only interpretation of this assertion I can find to make sense of it:
This is as a hidden assumption of the truth of Cartesian Dualism (thought/reason are necessarily properties of an existing mental substance and cannot be the outgrowth of a physical substance).
Is it just me, or do theists always try and hide this particular assumption? I think they don’t make it explicit for propaganda reasons (to explicitly state Cartesian Dualism opens it up to debate). But, assuming it as though it were self evident, makes an argument based on it seem stronger than it actually is.
"If life is the result of evolution, then it means that an evolutionist’s brain is simply the outworking of millions of years of random-chance processes."
Strawman Evolution is not a “random” process. Mutations are random, but selection is not. The traits of an organism resulting from mutation that make it better adapted for survival are preserved -- which traits are selected is determined by environment and competition. True, selection is not a goal oriented process, but that doesn’t mean it is random.
"The brain would simply be a collection of chemical reactions that have been preserved because they had some sort of survival value in the past."
This sounds a lot like the fallacy of composition to me.
If evolution were true, then all the evolutionist’s thoughts are merely the necessary result of chemistry acting over time. Therefore, an evolutionist must think and say that “evolution is true” not for rational reasons, but as a necessary consequence of blind chemistry."
This is a little vague, but I’ll respond to what I think it may be getting at.
This seems to be a circular argument that reason can only be the property of a non-physical, non-deterministic mind. It simply appeals to its own assumption (that “blind chemistry” cannot be rational) to prove its point.
