Frankfurt Cases

1. Introduction

Frankfurt cases are a family of thought experiments used to challenge the Principle of Alternative Possibilities (PAP), according to which a person is morally responsible for what they have done only if they could have done otherwise. They typically feature a counterfactual controller who is prepared to intervene to ensure that an agent performs a particular action, but who does not actually intervene in the scenario as described.

The central claim these cases are designed to motivate is that an agent can be morally responsible for an action even when no genuine alternative course of action is available to them. If so, PAP is not a necessary condition for moral responsibility. This has made Frankfurt cases a focal point in debates about free will, moral responsibility, and the compatibility of responsibility with determinism.

The discussion surrounding Frankfurt cases has developed into several distinct but interconnected strands: disputes over whether the cases really eliminate all alternatives, arguments about their metaphysical coherence, different ways of revising or replacing PAP, and applications to legal responsibility and everyday moral judgment. Supporters and critics alike now treat Frankfurt-style scenarios as standard tools for testing theories of agency, control, and responsibility.

Subsequent sections in this entry examine the origin of Frankfurt cases, the historical context in which they appeared, the exact nature of PAP, the canonical structure of Frankfurt’s original example, influential variants and refinements, and the main lines of philosophical response from compatibilist and incompatibilist perspectives.

2. Origin and Attribution

Frankfurt cases are attributed to the American philosopher Harry G. Frankfurt (1929–2023). They first appeared in his influential article:

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“Alternate Possibilities and Moral Responsibility”
— Harry G. Frankfurt, The Journal of Philosophy 66(23):829–839 (1969)

In that paper, Frankfurt set out explicitly to challenge PAP and to weaken a widely used argument from PAP to the incompatibility of moral responsibility with determinism. Frankfurt’s originality lay not in formulating PAP—that principle was already common in discussions of free will—but in proposing a systematic strategy for producing purported counterexamples.

Key Contributions of Frankfurt’s 1969 Paper

Frankfurt’s article is generally credited with:

• Formulating Frankfurt-style counterexamples: carefully designed scenarios pairing moral responsibility with an apparent absence of alternatives.
• Distinguishing between explanations of responsibility that rely on alternative possibilities and those that appeal instead to the actual sequence of deliberation and action.
• Proposing a weakened version of PAP (sometimes labeled PAP* in later literature) that applies only when the agent’s lack of alternatives is due to certain kinds of constraint or coercion.

Attribution and Precedents

While Frankfurt is the acknowledged originator of “Frankfurt cases” in their contemporary, systematic form, some scholars have noted earlier anticipations:

Most commentators hold that these antecedents do not diminish Frankfurt’s authorship of the Frankfurt-case framework itself, which introduced the now-standard pattern: an agent, an outcome-controlling intervener, and a setup in which responsibility seems preserved despite the absence of alternatives.

3. Historical Context

Frankfurt cases emerged in the late 1960s against a backdrop of intense debate over free will, determinism, and moral responsibility in analytic philosophy. At that time, many theorists—both compatibilist and incompatibilist—treated some version of PAP as a near-axiomatic starting point. Incompatibilists in particular often argued that if determinism is true, then no one ever has access to genuine alternatives, and hence no one is morally responsible.

Mid-20th Century Background

Several developments shaped the context in which Frankfurt’s proposal appeared:

Within this milieu, incompatibilist arguments frequently relied on PAP in combination with the claim that determinism eliminates alternatives. Frankfurt’s project targeted this argumentative structure rather than determinism itself.

Frankfurt’s Intervention

Frankfurt’s 1969 paper intervened by suggesting that PAP might be false independently of whether determinism is true. If responsibility can exist without access to alternatives, then the standard incompatibilist argument from determinism to the absence of responsibility loses a crucial premise. This move helped shift discussions away from leeway-based notions of freedom toward quality-of-will and reasons-responsive accounts, although those developments were fully articulated only in subsequent decades.

Historical scholarship typically views Frankfurt’s work as a turning point in responsibility theory, inaugurating an extensive literature on the relationships among alternatives, control, and the metaphysics of agency.

4. The Principle of Alternative Possibilities

The Principle of Alternative Possibilities (PAP) states, in Frankfurt’s formulation:

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“A person is morally responsible for what he has done only if he could have done otherwise.”
— Harry G. Frankfurt, “Alternate Possibilities and Moral Responsibility” (1969)

This principle captures an intuitive idea: holding someone responsible appears to presuppose that the person was not forced into their action but had a meaningful choice.

Interpretations of PAP

Philosophers distinguish several readings of “could have done otherwise”:

PAP has historically been invoked both descriptively (as capturing ordinary responsibility judgments) and normatively (as a requirement for just blame and punishment).

Motivations for PAP

Common motivations include:

• Fairness: It may seem unfair to blame someone for something they could not avoid doing.
• Deliberative practice: Our own experience of choice appears to involve considering multiple live options.
• Backward-looking justification: Responsibility is often linked to what the agent “could have done,” rather than merely what actually happened.

Frankfurt cases are designed precisely to test whether these motivations require PAP in its strong, leeway-involving form, or whether responsibility might sometimes persist even when no such alternatives exist.

5. The Classic Frankfurt Case

Frankfurt’s original paper does not offer a single “canonical” story but describes a type of case. Later presentations standardize it into a familiar narrative involving Jones and Black.

Standardized Jones–Black Scenario

A common reconstruction runs roughly as follows:

1. Black’s goal: Black wants Jones to perform a specific action—for example, to vote for Candidate A.
2. Black’s capacity: Black has installed a reliable mechanism (such as brain-monitoring equipment or advanced psychological control) enabling him to detect whether Jones is about to decide against voting for A.
3. Intervention plan: If Jones shows any sign of deciding or beginning to act otherwise (e.g., intending to vote for B or to abstain), Black will intervene instantaneously, manipulating Jones’s mental or physical processes to ensure that Jones votes for A.
4. Actual sequence: In the actual course of events, Jones, acting from his own deliberation and reasons, decides to vote for A. Black, monitoring the situation, never needs to intervene.
5. Modal setup: Despite the absence of actual intervention, it remains true that Jones could not have done otherwise, because any divergence would have triggered Black’s control, guaranteeing the same outcome.

Proponents of Frankfurt’s argument claim that Jones is intuitively morally responsible for voting for A: his decision expresses his own reasons and character, and Black’s presence plays no causal role in the actual sequence. Yet, given Black’s standing readiness to intervene, Jones allegedly lacks alternative possibilities.

Role of the Intervener

The counterfactual intervener Black is central: he is designed to block all relevant alternatives without affecting the actual choice. How exactly Black manages this (via prior signs, brain scans, or other mechanisms) varies across versions, but the core structure—a counterfactual threat of intervention that never materializes—remains the template for Frankfurt-style cases generally.

6. Logical Structure and Intuitive Pull

Frankfurt cases function as intuition pumps in an argument against PAP. Their logical structure can be schematically represented as follows:

Intuitive Pull

The persuasive force of Frankfurt cases depends on two main intuitions:

1. Responsibility intuition: The central agent appears to act from their own reasons, without coercion or manipulation in the actual sequence. Many readers report the judgment that such an agent is blameworthy (or praiseworthy) just as in an ordinary case without an intervener.
2. No-alternative intuition: The presence of a perfectly reliable intervener seems to ensure that, across the relevant range of possibilities, the agent could not have done otherwise. Any deviation would have been preempted.

Proponents argue that these two intuitions jointly pressure us to abandon or revise PAP: if one accepts that the agent is both responsible and without alternatives, then PAP cannot be a necessary condition of responsibility.

Sources of Disagreement

Critics challenge one or both of these intuitions. Some contend that closer analysis reveals residual alternatives (e.g., the ability to try to do otherwise), thereby undermining the no-alternative premise. Others argue that, once we appreciate the intervention setup, our initial responsibility intuition should be rejected or reinterpreted. The subsequent literature largely turns on which intuition, if any, should give way and how best to model the underlying structure of control and ability.

7. Key Variations and Refinements

After Frankfurt’s 1969 paper, philosophers developed numerous variations of Frankfurt cases to clarify, strengthen, or criticize the original argument.

Types of Variations

1. Different forms of intervention
   Some scenarios use direct brain stimulation, others intricate psychological conditioning, still others divine or demon-like foreknowledge and manipulation. These differences aim to avoid worries about physical possibility or covert manipulation of the agent’s will.

2. Timing of intervention
   Cases vary in when intervention would occur:

   • Pre-decisional: Black intervenes if Jones is about to form an intention contrary to Black’s goal.
   • Post-intentional: Black intervenes if Jones, already intending to comply, is about to refrain from acting.
     Adjusting timing is often used to address “prior-sign” and “flicker of freedom” concerns.

3. Positive vs. negative responsibility
   Some cases involve blameworthy actions (e.g., an assassination), others praiseworthy deeds (e.g., saving a child). This is intended to show that the alleged independence from alternatives applies to both blame and praise.

4. Overdetermination vs. preemption structures
   Philosophers distinguish cases where the intervener’s mechanism would be a backup cause, never activated unless the agent deviates (preemption), from cases where both the agent and intervener are simultaneous sufficient causes (overdetermination). Preemption-style cases are often preferred for challenging PAP.

Refinements Aimed at Objections

Many refinements directly respond to specific criticisms:

Authors such as John Martin Fischer, David Hunt, and others have proposed increasingly elaborate cases—sometimes involving neuroscientific or science-fictional technologies—to test the robustness of the anti-PAP argument. Opponents, in turn, adapt their critiques to these refinements, leading to a highly intricate dialectic over what an ideal Frankfurt case would require.

8. Actual-Sequence vs. Alternative-Possibility Theories

Frankfurt cases have crystallized a major distinction in theories of moral responsibility: actual-sequence views versus alternative-possibility (or leeway) views.

Alternative-Possibility (Leeway) Theories

These theories maintain that:

• Responsibility fundamentally depends on the agent’s having genuine alternatives at the time of action.
• PAP, or some close relative, captures a necessary condition for responsibility.
• Evaluating responsibility requires assessing not only what actually happened, but also what the agent could have done instead.

Libertarian and many incompatibilist theories typically fall into this category, insisting that robust leeway is indispensable.

Actual-Sequence Theories

In contrast, actual-sequence theories, often compatibilist, focus on features of the actual causal and deliberative history:

• What matters is whether the action issues from the agent’s own reasons-responsive mechanisms, character, or evaluative commitments.
• Alternative possibilities may be helpful or typical in ordinary circumstances, but they are not deemed necessary.
• Frankfurt cases are treated as paradigms where responsibility is grounded entirely in the actual sequence, despite the lack of alternatives.

John Martin Fischer and Mark Ravizza’s account of guidance control, and various quality-of-will theories, are prominent examples.

Relationship Between the Two Approaches

The impact of Frankfurt cases on this divide can be summarized as follows:

Some intermediate positions attempt to integrate elements of both approaches—for instance, by allowing that responsibility in many everyday cases involves alternatives, while maintaining that the deepest grounding lies in sourcehood or actual-sequence properties.

9. The Flicker of Freedom Debate

The flicker of freedom debate centers on whether Frankfurt cases genuinely remove all alternative possibilities relevant to moral responsibility. Critics argue that, on careful analysis, there remains at least a minimal alternative—a “flicker”—that can sustain PAP.

The Flicker Objection

Proponents of this objection, such as David Widerker and Carl Ginet, suggest that even in sophisticated Frankfurt cases:

• The agent typically has the ability to try to do otherwise, or
• There is at least a distinct possible beginning of a decision or intention incompatible with the actual outcome.

For example, in a Jones–Black case, it may be that Jones could have begun to form an intention not to vote for A, even if Black would immediately intervene at that point. This initial “trying” or “beginning to choose otherwise” is itself an alternative possibility.

If such a flicker remains, PAP can be reformulated so that responsibility attaches to this minimal alternative. Responsibility for the actual action is then said to derive from the agent’s control over this prior or nearby alternative step, thereby preserving a suitably refined PAP.

Responses to the Flicker Strategy

Defenders of Frankfurt cases respond in different ways:

The debate turns partly on how to individuate actions and abilities: whether “trying to do otherwise” is itself a distinct action with moral significance, and whether such a try is genuinely available in a successful Frankfurt case. No consensus has emerged, making the flicker debate one of the most persistent points of contention in the Frankfurt-case literature.

10. Metaphysical and Modal Challenges

Beyond flicker-based criticisms, another family of objections questions whether genuine Frankfurt cases are metaphysically possible or coherent.

Coherence of the Intervener’s Knowledge and Powers

One concern focuses on how the intervener could reliably know that the agent is about to choose otherwise:

• If the world is deterministic, the agent’s future decision may be predictable from prior states, but then, critics argue, the case risks building in determinism and may not generalize to indeterministic settings.
• If the world is indeterministic, it is unclear how the intervener could have infallible knowledge of an undetermined future choice without either collapsing into determinism or invoking problematic forms of foreknowledge.

Some critics (e.g., Ginet) argue that positing a mechanism that both perfectly tracks upcoming choices and leaves the agent’s responsibility intact may be internally unstable.

Preemption, Overdetermination, and Causation

Others question the causal structure required:

• Preemption scenarios must ensure that the intervener’s disposition constrains alternatives without actually causing the action.
• Some critics claim that when this structure is specified rigorously, either the intervener becomes a genuine cause of the action (threatening responsibility) or alternative possibilities reemerge.

Relatedly, worries about overdetermination arise if both the agent’s own decision and the intervener’s backup mechanism are sufficient causes of the action. Does such overdetermination still count as the agent’s lacking alternatives, or does it undermine the intended modal profile?

Modal Robustness and Accessibility

A further line of challenge questions whether the relevant counterfactuals (e.g., “If the agent were about to decide otherwise, the intervener would step in”) are sufficiently grounded in the metaphysics of laws and dispositions:

Proponents of Frankfurt cases often appeal to the permissiveness of science-fictional stipulations in thought experiments, maintaining that as long as no explicit contradiction is involved, the cases are legitimate. Critics counter that debates about moral responsibility should not rest on scenarios whose metaphysical underpinnings are so unclear or fragile.

11. Frankfurt Cases under Determinism and Indeterminism

Philosophers have explored how Frankfurt cases function in both deterministic and indeterministic settings, with some arguing that their force varies significantly depending on the background metaphysics.

Frankfurt Cases in a Deterministic World

Under determinism, every event, including human decisions, is fully determined by prior states and laws. In this context:

• Some compatibilists view Frankfurt cases as showing that even if determinism rules out alternatives, responsibility can still be grounded in the actual sequence.
• Critics respond that the cases add little to the standard compatibilist strategy: if determinism already ensures that the agent could not have done otherwise, the intervener seems redundant.

There is also a concern that, under determinism, the intervener’s role becomes obscure: if the agent was determined to act as they did, Black’s backup mechanism never had a genuine chance to operate, raising questions about the modal interpretation of “could not have done otherwise.”

Frankfurt Cases in an Indeterministic World

The more contentious issue is whether Frankfurt-style arguments succeed in an indeterministic world, where choices are not fully fixed by prior states.

Here the prior-sign problem becomes central: for Black to intervene only if Jones is about to choose otherwise, there must be reliable indicators of Jones’s impending decision. Objections include:

• If these prior signs are deterministically linked to the later choice, then a determinism-like structure has been smuggled in.
• If the connection is indeterministic, then Black cannot be guaranteed success, so it may remain possible for Jones to do otherwise even in the presence of Black’s mechanism.

Responses include introducing special kinds of signs, probabilistic intervention plans, or non-standard causal structures to maintain both indeterminism and the efficacy of the intervener.

Comparative Assessment

The dialectic can be summarized as:

This has led some philosophers to conclude that Frankfurt cases, if successful at all, operate most cleanly in a deterministic framework, while others maintain that appropriately designed cases can be made to work even under robust indeterminism.

12. Compatibilist Responses and Semi-compatibilism

Compatibilists—those who hold that moral responsibility is compatible with determinism—have often embraced Frankfurt cases, treating them as tools for shifting the focus of responsibility away from leeway and toward the quality of the actual sequence.

Actual-Sequence Compatibilism

Building on Frankfurt’s insights, several compatibilist theories argue that:

• What matters for responsibility is that the action issues from the agent’s own reasons-responsive capacities or from mechanisms the agent “owns.”
• The presence or absence of alternative possibilities is at most contingently related to responsibility, not a necessary condition.

John Martin Fischer and Mark Ravizza’s theory of guidance control is a prominent example. On their account, an agent is responsible when:

1. The behavior is generated by a moderately reasons-responsive mechanism.
2. The agent has taken ownership of this mechanism through a suitable historical process (e.g., learning, reflection, moral education).

Frankfurt cases are used to illustrate how an agent may retain guidance control even when no leeway remains.

Semi-compatibilism

Fischer introduces semi-compatibilism, the view that:

• Moral responsibility is compatible with determinism.
• Free will understood as leeway freedom (having genuine alternatives) might still be incompatible with determinism.

On this picture, PAP is rejected as a condition for responsibility but may still be relevant to certain conceptions of free will. Frankfurt cases are often cited as showing that responsibility can, in principle, be detached from leeway, thereby supporting the semi-compatibilist separation of issues.

Other Compatibilist Strategies

Other compatibilists accept some lessons of Frankfurt cases but respond differently:

Despite internal differences, these compatibilist and semi-compatibilist positions typically treat Frankfurt-style scenarios as either evidence or at least useful conceptual tools for decentering PAP in responsibility theory.

13. Libertarian and Incompatibilist Replies

Libertarians and other incompatibilists—those who deny that moral responsibility is compatible with determinism—have developed several strategies for resisting the implications of Frankfurt cases.

Defending PAP

Many incompatibilists argue that PAP, or something close to it, remains essential:

• They contend that our deepest intuitions about fairness, choice, and deliberation support the idea that responsibility requires robust alternatives.
• On this view, Frankfurt cases either fail to eliminate all alternatives (the flicker of freedom approach) or misdescribe our genuine responsibility judgments.

Some libertarians, such as Robert Kane, maintain that even if Frankfurt cases appear psychologically compelling, they should not outweigh a principled commitment to the role of indeterministic choice points in grounding ultimate responsibility.

Reinterpreting Frankfurt Cases

Another line of response is to reinterpret what successful Frankfurt cases would show:

In this way, some incompatibilists accept part of Frankfurt’s challenge while preserving a central role for alternative possibilities in their preferred conception of free will.

Metaphysical and Modal Critiques

Incompatibilists also emphasize the metaphysical and modal worries discussed earlier:

• If Frankfurt cases presuppose determinism, they cannot undermine libertarian views that deny determinism.
• If they are set in an indeterministic world, interventions that guarantee a single outcome may be metaphysically suspect.

From this perspective, Frankfurt cases are seen as illuminating but ultimately inconclusive thought experiments, whose apparent force depends on questionable assumptions about ability, causation, and possibility. Incompatibilists thus continue to argue that their broader theories—often built around undetermined, leeway-involving choices—remain intact despite the Frankfurt-style challenges.

14. Applications to Law and Moral Practice

Beyond theoretical debates, Frankfurt cases have influenced discussions about legal responsibility and everyday moral evaluation. Scholars in legal theory and applied ethics have used Frankfurt-style reasoning to probe the relationship between control, coercion, and excuse.

Legal Responsibility and Coercion

Many legal systems already distinguish between:

• Actions performed under duress or coercion, which can mitigate or exclude liability.
• Actions performed voluntarily, even when options are constrained (e.g., choosing between two lawful acts).

Frankfurt cases raise questions about whether legal responsibility should track:

• The presence of alternative options open to the defendant, or
• The quality of the actual decision-making process and the agent’s mental state (intent, recklessness, negligence).

Some legal theorists suggest that, in line with Frankfurt-style insights, liability may be appropriately grounded in whether the defendant acted with a culpable mental state, even when realistic alternatives were absent.

Everyday Moral Judgments

In ordinary moral practice, people sometimes assign responsibility in contexts where options are constrained—for example:

• A parent who had no realistic opportunity to avoid a minor harm but acted from clear indifference.
• An official whose institutional role severely limits choices yet who endorses and identifies with a harmful policy.

Frankfurt-style thinking has been invoked to argue that responsibility judgments in such cases often track quality of will rather than available alternatives.

Normative Implications

There is, however, no consensus on how far these insights should reshape law and practice:

Some interdisciplinary work explores whether jurors’ and laypeople’s intuitions about responsibility in Frankfurt-like scenarios align more closely with actual-sequence or alternative-possibility theories, using experimental methods to test folk judgments under constrained-choice conditions.

15. Legacy and Historical Significance

Frankfurt cases have become a standard point of reference in contemporary philosophy of action and moral responsibility, with a legacy that extends beyond the specific question of PAP.

Impact on Responsibility Theory

Their historical significance includes:

• Shifting the agenda: Moving debates from a near-exclusive focus on leeway and PAP toward actual-sequence properties, such as reasons-responsiveness, guidance control, and quality of will.
• Stimulating new distinctions: Encouraging finer-grained distinctions between free will and moral responsibility, sourcehood and leeway, and regulative control and guidance control.
• Inspiring semi-compatibilism: Providing a key motivation for theories that detach responsibility from leeway freedom while remaining agnostic about the compatibility of determinism with free will.

Influence Across Subfields

Frankfurt-style reasoning has influenced several areas:

Ongoing Controversies

Despite their prominence, Frankfurt cases remain controversial:

• Some philosophers regard them as decisive against PAP.
• Others see them as valuable but ultimately inconclusive tests of our intuitions.
• Still others question their coherence or relevance to real-world responsibility.

Whatever one’s assessment, the emergence of Frankfurt cases in 1969 is widely regarded as a watershed moment in late 20th-century analytic philosophy, reshaping how philosophers conceptualize freedom, control, and the grounds of moral responsibility.