Philosophy of Law Spring 2022

The Case of Kevin


We are going to talk about the case of “Kevin” as presented by Radiolab. Kevin’s behavior changed suddenly after his brain was altered. That seems like good reason to think that it was his brain that was responsible for his crimes rather than him. That is, roughly, an incompatibilist story: if you can blame the brain, you can’t blame the person.

On the other hand, he behaved in ways that suggests he met the standard tests for criminal liability. Compatibilists would be happier with that way of looking at it.

Necessary conditions on responsibility

What are the necessary conditions for being responsible for your actions, where “being responsible” means that you can be justly punished for what you did?

Incompatibilists say the necessary condition is that you are the cause of your behavior, free from any other causes outside of your control. If this is right, you can’t be held responsible for your behavior if it is caused by anything outside of your control.

The law, as described by Morse, maintains that the necessary condition is rationality: you can be responsible for what you did only if you were rational when you did it. In this way, the law is compatibilist: it holds that rationality is the only necessary condition for being responsible for your behavior. If so, you can be responsible for your behavior even if it is caused. All that has to be true is that you were rational when you did it.

We will start off the class with two more detailed statements of what rationality involves. These come from attempts to devise criteria for determining when insanity is a defense against a criminal charge.

  1. Knowledge of (a) right and wrong and (b) what you are doing. This is the M’Naghten Rule. It is widely used in the US.
  2. Knowledge and control of your behavior in the light of what you know. This is the position of the American Law Institute. This is a proposal to reform the standards used in the US.

What would these rules say about Kevin?

The big picture

If we’re going to say that Kevin should not be punished because his brain was responsible rather than him, then we are on the road to saying that no one can be punished. After all, everyone’s brain is responsible for their behavior. At least, that’s what materialistic neuroscience seems to be on the road to showing someday.

That said, it struck me that few of the people in the story said anything like that. Kevin, his wife, the judge, and the prosecutor all applied the compatibilist standards of rationality. They were primarily interested in whether he was capable of controlling his behavior in the light of his knowledge of right and wrong, which is the American Law Institute standard for rationality.

Everyone agrees on the facts of the case. What is at issue is how we understand or interpret them. That is where philosophy comes in. If we interpret the story of Kevin as showing that punishment is inappropriate because his actions were caused by his brain, we are headed towards incompatibilism. If we interpret the story as showing that the law’s normal standards for assessing rationality and insanity can be applied to a case like this, then we are taking up a compatibilist position.

Key concepts

  1. The facts of Kevin’s case
  2. The difference between the M’Naghten Rule and the American Law Institute’s rules
  3. Do you interpret Kevin’s case in an incompatibilist way or a compatibilist one? That is, do you think he should not be blamed because his brain injuries are responsible for his behavior or do you think the law’s normal standards can be appropriately applied to his case?


Oliver Sacks wrote up a description of what appears to be the same case, calling Kevin “Walter B”.

If you would like to see someone undergoing brain surgery while playing the flute, we have you covered.