Frankfurt cases (also known as Frankfurt counterexamples or Frankfurt-style cases) were presented by philosopher Harry Frankfurt in 1969 as counterexamples to the principle of alternate possibilities (PAP), which holds that an agent is morally responsible for an action only if that person could have done otherwise.
Principle of alternate possibilities
The principle of alternate possibilities (PAP) forms part of an influential argument for the incompatibility of responsibility and causal determinism, often called the core argument for incompatibilism. This argument is detailed below: PAP: An agent is responsible for an action only if said agent could have done otherwise. An agent could have done otherwise only if causal determinism is false. Therefore, an agent is responsible for an action only if causal determinism is false.
Traditionally, compatibilists (defenders of the compatibility of free will and determinism, like A. J. Ayer, Walter Terence Stace, and Daniel Dennett) reject premise two, arguing that, properly understood, free will is not incompatible with determinism. According to the traditional compatibilist analysis of free will, an agent is free to do otherwise when he would have done otherwise had he wanted to do otherwise. Agents may possess free will, according to the conditional analysis, even if determinism is true. Critics point out that compatibilists are making a circular argument here: An agent is free if an agent is free. The incompatibilists believe that free will refers to genuine (e.g., absolute, ultimate) alternate possibilities for beliefs, desires, or actions, rather than merely counterfactual ones.
Frankfurt's objection
From the PAP definition "a person is morally responsible for what he has done only if he could have done otherwise", Frankfurt infers that a person is not morally responsible for what he has done if he could not have done otherwise – a point with which he takes issue: our theoretical ability to do otherwise, he says, does not necessarily make it possible for us to do otherwise.
Frankfurt's examples are significant because they suggest an alternative way to defend the compatibility of moral responsibility and determinism, in particular by rejecting the first premise of the argument. According to this view, responsibility is compatible with determinism because responsibility does not require the freedom to do otherwise.
Frankfurt's examples involve agents who are intuitively responsible for their behavior even though they lack the freedom to act otherwise. Here is a typical case: Suppose someone (Black, let us say) wants Jones to perform a certain action. Black is prepared to go to considerable lengths to get his way, but he prefers to avoid showing his hand unnecessarily. So he waits until Jones is about to make up his mind what to do, and he does nothing unless it is clear to him (Black is an excellent judge of such things) that Jones is going to decide to do something other than what he wants him to do. If it does become clear that Jones is going to decide to do something else, Black takes effective steps to ensure that Jones decides to do, and that he does do, what he wants him to do. Whatever Jones's initial preferences and inclinations, then, Black will have his way.
What steps will Black take, if he believes he must take steps, in order to ensure that Jones decides and acts as he wishes? Anyone with a theory concerning what "could have done otherwise" means may answer this question for himself by describing whatever measures he would regard as sufficient to guarantee that, in the relevant sense, Jones cannot do otherwise. Let Black pronounce a terrible threat... Let Black give Jones a potion, or put him under hypnosis... [o]r let Black manipulate the minute processes of Jones's brain and nervous system in some more direct way, so that causal forces running in and out of his synapses and along the poor man's nerves determine that he chooses to act and that he does act in the one way and not in any other...
Now suppose that Black never has to show his hand because Jones, for reasons of his own, decides to perform and does perform the very action Black wants him to perform. In that case, it seems clear, Jones will bear precisely the same moral responsibility for what he does as he would have borne if Black had not been ready to take steps to ensure that he do it. It would be quite unreasonable to excuse Jones for his action, or to withhold the praise to which it would normally entitle him, on the basis of the fact that he could not have done otherwise.