Greene and Cohen contend that the law is only superficially compatibilist. The law only requires the capacity for rational behavior as a condition of criminal liability. That is compatible with the causal determination of our actions. You can be rational and have your actions causally determined at the same time.
Greene and Cohen argue that we accept this superficially compatibilist condition for incompatibilist reasons. They claim that we think of the reasoning person as a non-physical mind, distinct from the physical brain (the view that mind and brain are distinct entities is called dualism).
Neuroscience, according to Greene and Cohen, will undermine this dualist picture of persons by explaining more and more of our behavior as the product of physical causes. As a result, they believe, we will abandon the retributivist parts of our practices of punishment. The retributive ideal is that punishment is reserved for the guilty: those who freely chose to do bad. In place of retributivism, they believe, we will take up a consequentialist approach to antisocial behavior. They think this is a good thing because they view consequentialism as the more humane approach to punishment.
Greene and Cohen claim to show that we are tacitly incompatibilists with their example of Mr. Puppet. The idea is that Mr. Puppet would not be held responsible for his actions because they were so clearly formed by the scientist. But, they reason, if we aren’t willing to hold Mr. Puppet responsible for behavior that was caused, we should not hold anyone responsible for their behavior. Why? Everyone’s behavior is caused.
We talked about this case for some time. In my opinion, it is the critical part of Greene and Cohen’s argument. We are supposed to think that Mr. Puppet is not responsible and that is supposed to show that we are incompatibilists without fully appreciating it. Without Mr. Puppet, I don’t see that they have another way of showing that people are implicitly incompatibilists.