Here’s what we have so far.
Neurobiology seems to make free will impossible, even if full proof of a causal chain between brain and behavior still lies in the future. Ben Libet did not have such proof.
Nevertheless, that such a causal chain must eventually be found is a foundational asssumption of neurobiology.
Neurobiology is inherently dualistic, not materialistic. The type of dualism is epiphenomenalism. (“Some distinguished neurologists, such as Charles Sherrington (Man on his Nature 1940) and John Eccles (with Karl Popper, The Self and its Brain 1977) have continued to defend dualism as the only theory that can preserve the data of consciousness.” https://plato.stanford.edu/entries/dualism/)
Epiphenomenalism excludes free will, agency and mental causation.
Therefore, to resurrect free will, agency and mental causation, we must defeat epiphenomenalism. The argument in favor of free will starts with the argument against epiphenomenalism. Let’s take a look at the overall situation using various articles in the Stanford Encyclopedia of Philosophy.
In the SEP entry Dualism, https://plato.stanford.edu/entries/dualism/, Howard Robinson says “there are at least three serious problems for epiphenomenalism.”
- Profoundly counterintuitive. “What could be more apparent than that it is the pain that I feel that makes me cry, or the visual experience of the boulder rolling towards me that makes me run away? At least one can say that epiphenomenalism is a fall-back position: it tends to be adopted because other options are held to be unacceptable.”
- Evolution. “If mental states do nothing, there is no reason why they should have evolved.”
- Other minds. If mental states have no effect on behavior, then the behavior of other people gives us no evidence that they have mental states. Since no other kind of evidence is available, the other minds problem becomes permanent.
None of the three problems are obviously fatal for epiphenomenalism. It’s hard to overstate how strange a view of the world epiphenomenalism would be. But being counterintuitive is not regarded as a problem for physics. Maybe the truth is that the real nature of the world is very different from what we think it is.
The evolution argument assumes that consciousness could not become such a major part of life without undergoing evolution. Mental states would have to be considered “spandrels”: features which tag along in evolution but what are not themselves adaptive. https://better-questions-than-answers.blog/2018/06/19/the-mind-body-problem-part-i/ This would make consciousness incidental to the nervous system, which does have real effects on the world and did evolve. Why aren’t we “zombies”? (“Zombies in philosophy are exactly like us in all physical respects but without conscious experiences: by definition there is ‘nothing it is like’ to be a zombie. Yet zombies behave just like us, and some even spend a lot of time discussing consciousness.” https://plato.stanford.edu/entries/zombies/) We could go about our bio-chemical business without consciousness. That’s the question built into neuro-biology. In any event, there are many spandrels in evolution and there is no reason consciousness cannot be one too.
The Other Minds problem is not a problem only for epiphenomenalism.
The problem of other minds is the problem of how to justify the almost universal belief that others have minds very like our own. It is one of the hallowed, if nowadays unfashionable, problems in philosophy. Various solutions to the problem are on offer. It is noteworthy that so many are on offer. Even more noteworthy is that none of the solutions on offer can plausibly lay claim to enjoying majority support. https://plato.stanford.edu/entries/other-minds/
The SEP entry on Other Minds does not mention epiphenomenalism at all. It concludes that no solution to the other minds problem appears readily available. Using any proposed solution as an argument against epiphenomenalism is not promising.
The standard solutions have been outlined and the various critical responses discussed. What is clear is that there does not seem to be what might be called a received solution to the problem. It has been argued that the problem cannot be removed, nor can it be made easier to solve, by embracing any particular philosophy of mind.
Meanwhile, nobody likes epiphenomenalism. David Papeneau:
In itself, epiphenomenalism is not an attractive position. It requires us to suppose that conscious states, even though they are caused by processes in the physical world, have no effects on that world. This is a very odd kind of causal structure. Nature displays no other examples of such one-way causal intercourse between realms. By contrast, a physicalist naturalism about conscious states will integrate the mental realm with the causal unfolding of the spatiotemporal world in an entirely familiar way. Given this, general principles of theory choice would seem to argue strongly for physicalism over epiphenomenalism. https://plato.stanford.edu/entries/naturalism/
The problem for physicalism is that it integrates the mental realm into the physical causal structure by disintegrating the mental entirely. That’s how we got here in the first place.
Nobody is advocating for epiphenomenalism. It’s forced on us by neurobiology. The problem is to figure how to get out of it.