Lesson · Identity, Modality and Freedom · Freedom

Frankfurt Cases and the Ability to Do Otherwise

Black will make Jones act if Jones does not decide to, and Jones decides on his own. Jones could not have done otherwise, and yet his decision produced the act. The structural lab shows the decision is not a but-for cause of the act, and is a cause once Black's inaction is held fixed, and that is the case against the principle of alternate possibilities.

Open the interactive lesson Practice

PAP: responsible only if could do otherwise B = ¬D: Black acts if Jones does not decide A = D ∨ B: the act follows either flip D alone: A stays 1, not but-for hold B at 0, flip D: A is 0, a cause

Could not have done otherwise, and still the cause

Core ideas

What this lesson establishes

The previous lesson granted the incompatibilist a valid argument whose conclusion is that no one can do otherwise. This one asks whether responsibility needed that ability at all.

The principle of alternate possibilities

Call it PAP: a person is morally responsible for an act only if the person could have done otherwise. It is the premise that connects an inability to the loss of responsibility, and it seems obvious until a case is built to separate the two.

A counterfactual intervener

Black is ready to make Jones perform the act if Jones does not decide to. He never has to. Jones decides on his own, and the act follows. Black's readiness removes the alternative and takes no part in what actually happens.

Two tests of cause give two answers

The but-for test asks whether flipping the decision alone changes the act, and the answer is no. The holding-fixed test holds Black's inaction at its actual value and then flips the decision, and the answer is yes. The lab runs both.

The material

A model of the case

Three equations, the two tests, what they show, and the objection that Black has been described too kindly.

The principle of alternate possibilities has a long history of seeming obvious. If I could not have done otherwise, then what I did was not up to me, and it is hard to blame someone for what was not up to them. Harry Frankfurt built a case in which the first condition is false and the verdict about blame does not seem to follow.

Jones is deciding whether to shoot someone. Black wants him to, and has arranged things so that if Jones shows any sign of deciding not to, Black will bring about the decision and the act in Jones by a device. Jones does not show such a sign. He decides for his own reasons, and shoots. Black does nothing. Had Jones wavered, Black would have acted, so Jones could not have done otherwise.

Build the model with three variables. D says Jones decides to shoot, and is a given, true. B says Black acts, and Black acts exactly when Jones does not decide. A says the shooting occurs, and it occurs if either Jones decides or Black acts.

D = 1 Jones decides B = ¬D Black acts only if Jones does not decide A = D ∨ B the shooting occurs either way

At the actual values, D is 1, B is 0 and A is 1. Now run the but-for test of “Counterfactual Causation and the But-For Test” in Science, Induction and Causation. Flip D to 0. Then B becomes 1, because Black acts, and A is still 1. Flipping Jones's decision alone leaves the act in place, so the decision is not a but-for cause of the act. That is the formal content of “Jones could not have done otherwise”.

Definition · Holding a variable fixed

To test whether D is a cause once Black's inaction is held fixed, set B at its actual value, 0, and flip D with B kept there. If the act then changes, D is a cause holding B fixed, and B is the witness.

Hold B at 0 and flip D to 0. Now A = D ∨ B is 0 ∨ 0, which is 0. The act does not occur. With Black's inaction fixed, the act depends on Jones's decision, and the lab reports D as a cause holding B fixed. This is the structure of preemption: Black is a backup that was never used, and a backup never used does not take the credit from the decision that did the work.

Frankfurt's conclusion is that Jones is responsible for the shooting, though he could not have done otherwise, because the act issued from his own decision in the actual sequence of events, and Black played no part in it. If so, PAP is false. The ability to do otherwise was never what grounded responsibility; the actual source of the act was.

Has Black been described too kindly?

The case has been pressed hard. One reply says that Black must read some sign to know whether to act, and that the agent could have shown the sign or not, a small alternative that is enough for responsibility. Another says that if the sign reliably predicts a decision that Jones has not yet made, then determinism has been assumed about Jones's choice, and the case begs the question against the libertarian who denies it. The model leaves both open. Its equation B = ¬D gives Black a perfect reader, which is exactly what the objections dispute.

Two further points. The case does not make anyone free in the sense of the previous lesson, since it grants that Jones cannot do otherwise. A philosopher can hold that determinism removes the ability to do otherwise, as the consequence argument says, and still hold that this does not remove responsibility. The position is called semi-compatibilism. Second, the lab computes a verdict about causes in the model, and whether the model fairly describes Jones is the question the case turns on.

Interactive

Causes in a structural model

But-for, held fixed, and joint

Flip the decision, then hold Black's inaction

The table has three columns: the actual values, the values after the cause is flipped, and the values after it is flipped with the witness held at its actual value. In the first model, change the cause menu from D to B to see what Black is. In the third, Jones does not decide and Black acts, and the cause to test is Black.

Model

Equations, separated by semicolons

Exogenous settings

Candidate cause

Effect

The effect, actually—

But-for—

Halpern–Pearl—

Kind—

An equation is F = D & ~G; settings are S1=1 G=0. A variable without an equation is exogenous and needs a setting.

Method

Testing responsibility without alternatives

Five moves for any case built to remove the ability to do otherwise.

Name the decision, the backup and the act

In a Frankfurt case there are three: what the agent decides, what the intervener would do, and what happens. Give each a variable.

Write the backup as a conditional on the decision

The intervener acts only if the agent does not. That is B = ¬D, and it is the sentence that takes away the alternative.

Run the but-for test

Flip the decision alone and recompute. If the act survives, the agent could not have done otherwise, in the model's sense.

Hold the backup at its actual value and flip again

If the act now changes, the decision is a cause holding the backup fixed, and the intervener, who did nothing, has not displaced it.

Ask whether the model is fair

Check what the intervener reads, and whether the reading assumes the agent's choice is settled in advance. If it does, the case may beg the question.

Alternatives and causes

Score 0 / 0

Choose the answer you can justify.

Jones, Black and the shooting

Jones decides. Black acts only if Jones does not. The act occurs if either does.

actual: D = 1, B = 0, A = 1 flip D to 0: B becomes 1, A = 0 or 1 = 1 flipping D alone leaves A at 1: not but-for hold B at 0, flip D to 0: A = 0 or 0 = 0 holding B fixed, D flips A: D is a cause Jones could not do otherwise; he is still the cause

The two tests disagree, and that is the point of the case. The but-for test records the absence of an alternative. The holding-fixed test records where the act came from. The dispute is about which of the two grounds responsibility.

Common mistakes

Thinking responsibility requires that the agent could have done otherwiseIn the model Jones cannot: flipping his decision leaves the act at 1, because Black's device takes over. Yet with Black's actual inaction held fixed, flipping the decision flips the act, so the decision is the cause of the shooting. The belief that responsibility needs an alternative has a counterexample if the case is fair.

Thinking Black's presence makes Jones's decision irrelevant to the actBlack is a backup that was not used. The act came about through D, and the lab reports D as a cause holding B fixed. A spare tyre in the boot does not take over from the tyre that carried the car, and the structure is the preemption of the earlier course.

Treating the case as a proof that people are free or responsibleThe case argues against one premise, PAP. It assumes that Jones is responsible and that Black has been described fairly, and a reader who denies either is not refuted by the lab. Whether a deterministic world removes responsibility for another reason, such as that the source of the act lies outside the agent, is left open.

Check your understanding

✓

Finish when you can build a Frankfurt case as a structural model and report both tests of cause.

You should be able to write the equations for decision, backup and act, state whether the decision is a but-for cause, find the variable that must be held fixed for it to become a cause, and say which dispute about the case the model leaves open. A claim that the agent “is still the cause” without the witness has not been computed.

Note: The structural lab is Boolean and the equations are given by you. It cannot tell you that a real intervener could read a decision before it was made, and the objections to the case turn on exactly that.