Epiphenomenalism Leads to Contradiction
In our everyday life we take it for granted that our conscious states “cause” things to happen, just as we take consciousness itself for granted. No one normally questions the causal relationship between, say, the hunger for a tuna-fish sandwich and subsequent activities involving the contents of a refrigerator.
But then certain knowledge takes over. We “know” that all physical events are totally controlled by the laws of physics, so even if, in some sense, our desire for a sandwich causes us to manufacture and consume such an item, at some deeper level, all those events can be fully explained by the laws of physics: our purposeful behavior must ultimately be derivable from known scientific law.
Although the mechanists cannot believe it, this is an utterly untenable proposition. It is not possible to derive purpose from non-purpose. Purpose means consciousness causes things to happen; mechanistic systems, by their very nature, deny that consciousness can cause anything; therefore mechanistic systems cannot produce genuinely purposeful behavior.
That leaves the mechanists with epiphenomenalism: the idea that our sense of behaving with purpose is an illusion. But that also leads to a contradiction. The reason Darwinism is the lynch-pin of the mechanistic doctrine is that it provides a mechanical explanation for the apparent purposefulness of life. At every level, much to the embarrassment of biologists, who wish to be every bit as mechanistic as the physical scientists, life seems to behave purposefully. Metaphysical Darwinism does away with purpose and design. Behaviors and structures that seem purposeful were merely chosen mechanically by natural selection. If they enhance the organism's fitness to survive and reproduce, they are blindly selected as the unfit are culled out.
This leads to a contradiction. On the one hand, if physical law is complete and consciousness exists, then mental events do not change anything: epiphenomenalism is true. But if consciousness has no function, as epiphenomenalism insists, then it cannot possibly enhance the organism's fitness and there is no way that it could be chosen by natural selection. If epiphenomenalism is true, as Darwinism implies, then consciousness, a highly complex function of the brain, could not exist. Darwinism implies that consciousness does not exist. It does exist. Thus metaphysical Darwinism must be false.
So this is what we are left with, as consisely as possible: If consciousness exists and metaphysical Darwinism is true, then mind has no adaptive function. But Darwinism also insists that complex biological systems come into existence only by virtue of their function in enhancing survival and reproduction. So if metaphysical Darwinism is true, it follows that it is false; therefore it is false.