Van Inwagen vs. Frankfurt

Frankfurt attempts to argue for compatibalism.  He wants to show that moral responsibility and determinism are compatible.  In order to do this, he shows that a classic incompatibalist thesis, PAP, is false.  PAP is the principle that states that you are morally responsible for an action only if you could have done otherwise.  Frankfurt provides thought experiments that are meant to show that there will be times that a person is morally responsible even if he or she could not have done otherwise than they did.

Van Inwagen wants to defend incompatibalism.  He thinks that there is a principle better than PAP that is not vulnerable to the kind of counterexamples that Frankfurt provides.  Van Inwagen's new incompatbalist principle is PPP: you are morally responsible for a something only if you could have prevented that thing from happening.

Remember Jones and Black.  Jones has decided to assassinate the president, and Black has put a device in Jones' brain that will make him kill the president even if he decides not to go through with it.  This is supposed to show that PAP is false, since if the reason why Jones does what he does is because he wants to (and not because he is forced to), then we would hold him morally responsible even if he could not have acted otherwise.  But when we apply PPP to this case, the tension seems to be resolved.  Jones could not prevent himself from killing the president,  so he is not morally responsible for this action.  This is supposed to be a principle that is not disproven by a case like Jones and Black.

According to PPP, moral responsibility requires the possibility to prevent states of affairs from obtaining.  So if determinism is true, then there are no states of affairs that can be prevented.  So there is no state of affairs for which anyone is responsible.

Frankurt responds that to talk about the ability to prevent things as a condition for moral responsibility (as states in PPP) is to stop talking about free will.  Frankfurt says that free will only has to do with what actions I perform with my body---the consequences that arise as a result of my actions are irrelevant to my free will.