The manipulation argument

A designed agent who meets every condition compatibilism asks for still looks like a puppet, and the manipulation argument turns that reaction into the strongest case against compatibilism anyone has made.

The previous lesson moved the debate from alternatives to sourcehood. This lesson is what incompatibilists did with the new ground. The method is unusual and worth noticing in its own right: instead of a formal derivation like the Consequence Argument, it works by constructing a sequence of cases and daring the opponent to find a principled place to stop.

Professor Plum, four times

Derk Pereboom set out the argument in Living Without Free Will in 2001 and refined it in 2014. In each of four cases, Professor Plum kills Ms White for self-interested reasons. In each case he satisfies every condition compatibilists have proposed: his action flows from a moderately reasons-responsive mechanism, he acts on desires he reflectively endorses, he is not coerced, not compelled, not deceived, and his egoistic reasoning is the ordinary sort that many people engage in.

In the first case, a team of neuroscientists manipulates Plum's brain directly, by radio, in the moment: they produce his reasoning process as it happens, and the desire that issues from it is irresistible only in the sense that his own reasoning is, which is to say not irresistible at all in the compatibilist's sense.

In the second, the neuroscientists did their work at the beginning of Plum's life, programming him so that he reasons in a rationally egoistic way, a trait he had no control over acquiring. They then leave him alone, and thirty years later that programming issues, through his own deliberation, in the killing.

In the third, no neuroscientists exist. Plum's character was fixed by rigorous training from infancy, administered by his household and community, which produced the same rationally egoistic outlook by ordinary social means.

In the fourth, nothing unusual happened at all. Plum is an ordinary man in a deterministic world, and the state of the world before his birth, together with the laws, entails his killing Ms White.

The claim is that there is no principled difference between adjacent cases, and that most people judge Plum not responsible in the first. If the judgement is right and the cases really do shade into each other, the judgement carries through to the fourth, which is the situation every determined agent is in.

Pereboom's preferred formulation is not merely "you cannot draw a line". It is an inference to the best explanation: the best explanation of why Plum is not responsible in the first case is that his action traces to factors beyond his control, and that explanation applies word for word to the fourth.

The zygote

Alfred Mele's version, from Free Will and Luck in 2006, compresses the argument into a single case and is harder to wriggle out of.

A goddess, Diana, creates a zygote in Mary. She has a complete knowledge of the deterministic laws and of the state of the world, and she designs the zygote precisely so that, thirty years later, the resulting man Ernie will perform a particular action at a particular time. Ernie grows up normally. He deliberates in the ordinary way, satisfies every compatibilist condition, and does what Diana designed him to do.

Mele's argument then has three lines. Ernie is not responsible for that action. There is no relevant difference between Ernie and any ordinary agent in a deterministic world, since the only difference is that Diana intended the outcome and intentions of a distant third party do not change what happens inside Ernie. Therefore no agent in a deterministic world is responsible.

The second premise is what gives the argument its force. Everything Diana does is done by the initial conditions in an undesigned deterministic world too. She adds a designer's intention and subtracts nothing from Ernie.

Example. A compatibilist replies that Ernie is responsible after all, but that Diana is also responsible, as a puppet-master is. Does that answer the argument?

Not by itself, though it is a step. Shared responsibility is a familiar phenomenon: a person who deceives another into causing harm is culpable without the deceived party being wholly innocent, so the presence of a responsible designer does not by itself exculpate Ernie. But the argument does not need Ernie to be innocent because Diana is guilty. It needs Ernie to be relevantly identical to an undesigned determined agent, and the reply concedes exactly that by locating the difference in Diana rather than in Ernie. If Ernie is responsible, the compatibilist has answered the argument, and the reply about Diana is then a piece of bookkeeping rather than a defence.

Now you. A critic says the four-case argument is a sorites, like the paradox of the heap, and that sorites arguments are known to be fallacious. Is that a good objection?

The soft line: find a difference

The first family of replies accepts that Plum is not responsible in the early cases and looks for a condition he fails there and meets later. This requires historical compatibilism: the claim that whether an action is free depends not only on its structure at the moment of acting but on how the agent came to be that way.

Fischer and Ravizza's ownership condition, from the previous lesson, is one such attempt. Plum in the second case never took responsibility for his own mechanism in the required sense, because the mechanism was installed rather than acquired through his own experience of himself as an agent. John Christman's account of autonomy takes a similar route: a desire is autonomous when the process by which it was acquired is one the agent could endorse on reflection, and covert programming fails that test while an ordinary upbringing passes it.

The difficulty is always the same, and it appears between Pereboom's second and third cases. Community training in infancy is not something a child consents to, endorses at the time, or could have resisted. If it counts as ownership, then it is hard to see why programming that produces exactly the same psychology does not, and if it does not count, then very few actual human beings own their mechanisms, which concedes most of what the incompatibilist wanted. Every soft-line reply lives or dies on that junction, and none has produced a criterion that most philosophers accept.

The hard line: bite the bullet

The second family of replies, defended by Michael McKenna among others, denies the first premise. If Plum genuinely meets every compatibilist condition, then Plum is responsible in all four cases, manipulation included, and our reluctance to say so is a mistake with an explanation.

This sounds outrageous until the dialectic is made explicit. The argument asks us to accept a verdict about a case described in a way that is guaranteed to trigger a reaction: white-coated neuroscientists, radio control, a designer goddess. Nobody's intuitions were formed on such cases. McKenna's point is that the argument is only as strong as the initial judgement, and that the judgement is being made by people who have not yet absorbed the stipulation that Plum's deliberation is entirely normal. Since it is the incompatibilist who is arguing from intuition here, the burden is not obviously on the compatibilist.

What ordinary people say

There is empirical support for that diagnosis, and it is worth reporting with its limits. Eddy Nahmias and colleagues found in 2005 and 2006 that when ordinary people are given a determinist scenario described concretely, without the word "determinism", roughly three quarters judge the agent to have acted of his own free will and to be blameworthy. Shaun Nichols and Joshua Knobe found in 2007 that the framing matters enormously: asked abstractly whether people in a fully deterministic universe are fully morally responsible, 86 percent said no, while asked about a specific man in that universe who murders his family, 72 percent said he is fully morally responsible. Nahmias and Dylan Murray have argued that when people do read determinism as excluding responsibility, they are misreading it as bypassing, the idea that our beliefs and desires make no difference to what we do, which the second lesson of this course showed determinism does not claim.

The limits of that evidence should be stated. Surveys record what people say about vignettes, not what is true, and both sides can point to results favourable to them: Hagop Sarkissian and colleagues found in 2010 that in the United States, India, Hong Kong and Colombia alike, most people judged our own universe to be indeterministic and gave incompatibilist answers to abstract questions. The most that can be concluded is that ordinary judgements are unstable across framings, which weakens any argument that leans on their being obvious, and the manipulation argument leans on exactly that.

Example. Quantify the framing effect in the Nichols and Knobe result and say what it does and does not show.

In the abstract condition, 86 percent denied full responsibility, so about 14 percent affirmed it. In the concrete condition, 72 percent affirmed it. The same question about the same deterministic universe therefore moves by $72-14=58$ percentage points depending on whether it is asked in general terms or about a named man who burned his family. What that shows is that at most one of the two responses can be tracking the philosophical question, since the metaphysics is identical in both vignettes; something else is moving people, and the leading candidates are affective engagement in the concrete case and a bypassing misreading in the abstract one. What it does not show is which response is correct. A survey can demonstrate that an intuition is unreliable, which is a real and useful result, and it cannot supply the truth the intuition was supposed to deliver.

Now you. A compatibilist cites the Nahmias results as evidence that ordinary people are compatibilists. What is the strongest reply available to an incompatibilist?

Example. Take the hard line for a moment. What must a compatibilist say about the first case, and what is the cost?

They must say that Plum, whose reasoning is produced in real time by radio from a team of neuroscientists, is morally responsible for the killing, provided the process running in him is his own reasons-responsive deliberation and he endorses what it produces. The cost is high and should not be minimised: this is a case where blaming Plum feels like blaming the tool rather than the hand. The compatibilist's mitigation is that our reaction is being driven by the vividness of the manipulators and by the natural assumption that Plum is being overridden, and that once the case is stripped to what it actually stipulates, a deliberating agent acting on endorsed reasons, the verdict looks different. Whether that mitigation is enough is a judgement call, and it is exactly the sort of judgement call this course wants you to make explicitly rather than by feel.

Now you. Which reply, soft or hard, is available to a semi-compatibilist who has already given up the ability to do otherwise, and why does the manipulation argument threaten them at all?

Where the argument leaves things

The manipulation argument is the best case for incompatibilism about sourcehood, and it has not been refuted. Nor has it been established. Its critical premise, that Plum is not responsible in the first case, is exactly as strong as an intuition about an artificial case, and the experimental work shows such intuitions to be sensitive to how the case is put.

What it has certainly done is force compatibilism to become historical. Almost nobody now defends the view that the internal structure of an agent at the moment of acting is the whole story, and the interesting question has become which histories are disqualifying. That is a question the earlier lessons could not even ask.

There is also a warning in it for the other side. If the argument works, it works by showing that having your psychology installed by causes outside your control removes responsibility. That premise does not stop with determinism: it applies to indeterministic worlds too, since nobody chooses the undetermined events that shape them either. An incompatibilist who takes the manipulation argument seriously is under pressure to say what a free agent's history could possibly look like. That is the libertarian's problem, and it is the next lesson.