Before I go on, there are two things that I need to clarify from last time. First, when I said that psychology and neuroscience were soft sciences, I wasn't dissing them. I was just pointing out that these fields are not very quantitative. This is not due to any deficiencies of psychologists or neuroscientists, it's just a fact of how complex these sciences are. They are not as quantitative and well-defined as physics, which is well-described by a set of differential equations, and where the errorbars on measurements are very small, and where the agreement between quantitative measurements and mathematical models is high. This is unheard of in biology, much less psychology and neuroscience. So my point was how could any experiment in these fields of science disprove a long-standing law of logic?
Second, I realize now that I made it sound like Dr. Coyne's entire stance on free will is a result of these experiments on psychology and neuroscience. Upon further reflection, I realize that is not necessarily the case. More likely, Dr. Coyne is simply an atheist, and believes that we do not have anything about us that is immaterial. That is, we are our bodies, and we have no soul, no spirit, no "mind", etc., and thus have no free will. According to this worldview, we are determined by our chemistry. But now that we have these experimental results from psychology and neuroscience that Dr. Coyne is referring to, he believes this worldview has just been validated. However, like I said before, these experiments are extremely unlikely to have validated a self-contradiction.
Which brings us back to the original question: exactly how is Dr. Coyne's stance on free will self-contradictory?
The short answer is that if no one has free will, then Dr. Coyne did not arrive at his own conclusion based on his choice. His brain chemistry made him think we have no free will (and also made him an atheist).
The long answer is this. If we really have no free will, and everything we do is determined by chemistry, then nothing I believe is actually based on fact or reason. No decision I make, whether it is to accept Jesus Christ as my Lord and savior, or to eat a dark chocolate-covered peppermint Jo-Jo tonight for dessert, was based on reflection, careful thought, and reason. So, this begs the question, did Dr. Coyne arrive at his stance on free will based on scientific evidence and his own reasoning, as he claims?
Ironically, if his worldview is correct, then no, he did not. His brain chemistry simply dictated it. In other words, he may be correct, but it's only because of luck. Or perhaps, as the evolutionary biologist would have it, I just have the genes that make me believe in God, while Dr. Coyne has the genes to make him an atheist (that is of course a gross oversimplification of evolutionism's stance, but it works well enough for our discussion).
Of course, if this is true, that means that Dr. Coyne has zero evidence to back up his claim, even if he is right. He can try all he wants, but maybe he's actually not being rational about the evidence. Maybe he just has the brain chemistry that makes him believe that his evidence that we have no free will is rational.
This worldview then leads to a series of complete absurdities. How can I sit here and try to convince you of anything, when what I am typing doesn't even have any meaning (because I did not arrive at my own thoughts rationally; they just came from physics)?
The big question this always leads us back to is, if belief in God is false, then why do so many people believe in a god of one form or another? Why do so many people insist we have a spiritual component? I've written on this before, but it bears repeating because it is so germane to this topic of free will and determinism. The answer coming from the evolutionism camp is that at some point in the past, believing (falsely) in a god gave us some sort of fitness advantage (perhaps comforting us in our time of need?), and the fact that so many people still do today is simply a holdover from our evolutionary history.
This claim (besides having zero scientific evidence) is self-contradictory in the same way that Dr. Coyne's is. If sometimes we have false beliefs because of evolution, how can we be sure that any of our beliefs are true? How can we trust any of our reasoning capabilities? Maybe Dr. Coyne just got the genes that told him to be an atheistic evolutionist?
I propose that both of these (the argument from determinism and the argument from the evolutionary origin of belief in a god) are self-defeaters for naturalism.