Modern Compatibilism

Morse’s article tries to answer two challenges from neuroscience. The first challenge is that neuroscience seems to show that the brain causes behavior. The second challenge is that neuroscience seems to show that mental states like beliefs, desires, and intentions do not cause behavior.

He is especially worried about the second challenge because it threatens to undermine the legal standard for responsibility. The legal standard is rationality: people are liable to punishment only if they are rational. Rationality involves acting on one’s beliefs and desires: rational people act in ways that they believe will enable them to get what they want. If beliefs and desires do not cause actions, then rationality is irrelevant to how we behave and the legal standard of rationality is misconceived.

The law’s compatibilism

The law recognizes excuses for behavior that violates the criminal law. People who do not meet the standards of rationality cannot be punished for their actions.

What does it mean to be rational? The main component, according to Morse, concerns knowledge: rational people understand what the law requires and the nature of their own behavior (Morse 2010, 842). (We will talk more specifically about this in the next class, when we read proposed standards for the insanity defense.)

The law also recognizes external compulsion or coercion as an excuse. Those who break the law with a gun to their heads are excused even though they do not suffer from defects in their rationality. (Quite the contrary.)

This raises a question about what is sometimes called “internal” compulsion. Cases of internal compulsion involve people who cannot control their behavior. They do what they know to be wrong for reasons that, they maintain, are out of their control. Is internal compulsion an excuse and, if so, why? Morse treats these cases as defects of rationality (Morse 2010, 843). Morse’s presentation of his opinion is quite terse, so I am not entirely confident that I have him right. That said, the idea seems to be that cases of internal compulsion involve an inability to control one’s behavior in the light of what one knows to be right. So you can know what the law is and what your behavior involves but still suffer from a lack of rationality if you can’t bring your knowledge to bear on your actions. The idea is that these cases are similar to cases of external compulsion because it is unusually difficult for the person to make the correct choice. Consequently, the law excuses the behavior in both kinds of case.

The law excuses people who are subject to external and internal compulsion. The important thing for Morse is that the legal excuse cannot be generalized from these specific causes of behavior to all causes of behavior. So, he maintains, you can be excused if you were forced by a gun to your head but not if your behavior was the product of causal forces that originated with the big bang.

We will talk more about internal compulsion on Tuesday when we discuss the unfortunate Kevin.

The threat to folk psychology

What really worries Morse is the possibility that neuroscience will displace what he calls “folk psychology.” When we employ folk psychology, we explain people’s behavior as the product of their beliefs, desires, and intentions. Morse believes the law assumes folk psychology is accurate and that beliefs, desires, and intentions really do explain why people do the things they do.

That is how we can understand human actions as rational or irrational: do they reflect the person’s beliefs and desires or not? Your behavior is rational if it makes sense in the light of what you want to achieve and your beliefs about how to achieve it. If you want to go to lunch and you believe that the cafeteria is to the west of here, your behavior of walking west towards the cafeteria is rational. If you walk south despite believing there is no place to eat to the south, your behavior is irrational.

So if neuroscience displaces folk psychology in the way that the physical sciences have displaced folk physics, one of the assumptions the law relies on would have been shown to be false. That is what Morse worries about.

We spent a fair amount of time talking about the experiments done by Benjamin Libet (Libet 1999). These seem to show that the brain starts acting before the person is consciously aware of having decided to act. That suggests that the intention to act is not the cause of our actions: it happens after the brain takes the first steps to cause an action.

Libet himself has a libertarian view of free will on the grounds that neuroscience has shown that we have an unexplained ability to intervene in the causal chain between the brain’s activating to move the finger and the finger’s actually moving. In this way, he makes good on Matthew’s suggestion in the last class that neuroscience might support libertarianism rather than determinism, contrary to what Greene and Cohen believe. We talked very briefly about Libet’s idea that the conscious self can “veto” the brain’s decision to act as well as some of Morse’s criticisms of Libet’s work (Libet 1999, 51–53). (I put the Libet article on the sakai site; it’s optional, but people are usually interested.)

I ended with a suggestion that both Libet and Morse were wrong in assuming that folk psychology requires us to be conscious of our beliefs, desires, and intentions. I myself rarely explicitly think through exactly what I believe, desire, and intend before acting. But I have no doubt that my actions reflect those things. For example, I do not explicitly think “I would like some coffee now” each morning, much less “and I believe that I will get it if I put the kettle on the stove.” Nonetheless I think that those beliefs and desires explain why I put the kettle on the stove every morning.

What I’m suggesting is that the electrical activity that Libet’s experiment identified was the intention to move the hand. It’s just that the subjects were not consciously aware of intending to do that for several microseconds. If that’s right, Libet’s experiments do not threaten to displace the folk psychological concepts of belief, desire, and intention.

Key concepts

  1. How Morse answers the charge that the brain causes behavior.
  2. The rationality standard for punishment.
  3. Morse’s worry about the second charge, that “folk psychology” is not true.

Folk physics at work

Morse’s worry is that folk psychology is going to go the way of folk physics, that is, the explanations of physical phenomena that are good enough for everyday life but actually false.

I gave one example of folk physics: our belief that the table in the classroom is solid when, in fact, it is mostly empty space.

I referred to another bit of folk physics: heavy objects fall faster than light ones. I know that you know that Galileo showed this was false. But you are still going to be surprised to see it in action.


Libet, Benjamin. 1999. “Do We Have Free Will?” Journal of Consciousness Studies 6 (8–9): 47–57.

Morse, Stephen J. 2010. “Scientific Challenges to Criminal Responsibility.” In Philosophy of Law, edited by Joel Feinberg, Jules Coleman, and Christopher Kutz, 9th ed., 839–53. Belmont, CA: Wadsworth.