Non-Identity Problem

1. Introduction

The Non-Identity Problem is a philosophical challenge about how to evaluate actions whose main effect is to determine who will exist in the future, rather than how well particular already-determined individuals fare. It asks how such actions can be morally wrong when, for each person who actually comes to exist, the alternative would have been not to exist at all.

In many ordinary moral judgments, an act seems wrong because it harms someone by making that person worse off than they otherwise would have been. The Non-Identity Problem highlights cases—especially involving reproduction and long-term policy—where this comparative notion of harm appears not to apply, yet many people still regard the actions as morally troubling. Typical examples include:

• Choosing to have a child now rather than later, thereby causing a different child to exist.
• Adopting environmental policies that predictably alter who will be conceived many generations hence.
• Using reproductive technologies or genetic selection that determine which possible child becomes actual.

In these cases, if the resulting lives are judged “worth living”, each actual person may plausibly claim that, given the realistic alternatives, they are not worse off; had different decisions been made, they would simply never have existed. Still, many find it intuitive that some such decisions are morally objectionable.

The Non-Identity Problem, as standardly presented, therefore sits at the intersection of population ethics, moral theory, and personal identity. It raises questions about:

• Whether morality should be person-affecting, focusing only on harms and benefits to specific individuals.
• Whether there can be impersonal values that make one outcome better than another, even when no particular person is better or worse off.
• How to think about obligations to future generations whose existence depends on our present choices.

The problem has become a central tool for testing and comparing ethical theories, especially in discussions of reproductive ethics, environmental policy, and intergenerational justice.

2. Origin and Attribution

The Non-Identity Problem is most closely associated with Derek Parfit, who offered the first systematic and influential formulation in Part IV of his 1984 book Reasons and Persons. Parfit coined neither the general idea that identity-affecting choices pose moral puzzles nor all of the specific examples, but he brought these strands together into a clear argumentative structure that has shaped subsequent debate.

Parfit’s work is typically cited as the canonical source:

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We cannot claim that we have harmed these people. For if we had acted differently, these particular people would never have existed.

— Derek Parfit, Reasons and Persons (1984)

Parfit is usually credited with:

• Introducing the label “Non-Identity Problem” (and related expressions such as “non-identity cases”).
• Framing it explicitly as a challenge to person‑affecting and harm-based moral theories.
• Developing iconic thought experiments such as the 14-Year-Old Girl and Depletion cases.

While Parfit’s account is the reference point, subsequent philosophers have refined, expanded, or rebranded aspects of the problem. For example:

Despite these later contributions, encyclopedias, textbooks, and scholarly articles almost uniformly attribute the canonical statement and widespread recognition of the Non-Identity Problem to Parfit’s Reasons and Persons. Earlier discussions are usually treated as precursors rather than complete formulations.

3. Historical Context and Precursors

Parfit’s formulation emerged in the early 1980s against a backdrop of growing concern about nuclear risks, environmental degradation, and new reproductive technologies. Philosophers and policymakers were increasingly interested in duties to future generations, and in how large-scale policies would shape not only the quality but also the composition of future populations.

Earlier Philosophical Precursors

Several earlier discussions raised related issues without isolating them as the Non-Identity Problem:

Some legal and bioethical cases, especially wrongful life suits, already turned on the puzzle of whether a person could be said to have been harmed by being born into a disadvantaged condition when the alternative was never to exist. These disputes foreshadowed the comparative-harm issues central to non-identity discussions.

Intellectual Context in Moral Philosophy

Within analytic philosophy, several trends set the stage:

• The rise of population ethics and debates over total vs. average utilitarianism.
• Renewed interest in personal identity over time, influenced by Parfit’s own reductionist views.
• Early work on intergenerational justice, including how to justify obligations to distant future people.

These contexts made it natural to ask whether standard moral theories—often developed for fixed populations of determinate individuals—could handle choices that affect who comes into existence.

Parfit’s contribution is widely regarded as distinctive because he integrated these strands into unified, stylized thought experiments, explicitly posed the problem as one of non-identity, and connected it to systematic questions about the foundations of moral theory.

4. Core Formulation of the Non-Identity Problem

The core formulation centers on a tension between three elements:

1. A person-affecting or harm-based principle: wrongness requires making some particular person worse off than they otherwise would have been.
2. The observation that many future-regarding actions determine who will exist.
3. The widespread intuition that some such actions are morally objectionable even when no one seems made worse off.

In a standard non-identity case, an action—such as deciding when to conceive, or which environmental policy to implement—affects the timing, circumstances, or partners involved in conception. Given the sensitivity of conception to small variations, very minor changes typically lead to the existence of an entirely different individual. Thus:

• Under option A, one set of people will exist.
• Under option B, a different set will exist.

If those who exist under A all have lives worth living, they cannot, on a straightforward comparative account, claim they were harmed by A: had B been chosen, they would not have existed at all. The same holds symmetrically for people under B.

Yet many people judge that some such options—e.g., a short-sighted policy that predictably results in worse living conditions for future people—are seriously morally wrong or at least clearly worse options. This creates the puzzle: how can we reconcile these judgments with the person-affecting principle?

The Non-Identity Problem, in its basic form, does not presuppose a particular overall ethical theory; rather, it is framed as a challenge to any theory that:

• Grounds wrongness wholly in comparative harm to individuals, and
• Treats non-existence as no worse for a person than existence with a life worth living.

Different philosophers respond by revising one of these elements: rejecting the person‑affecting principle, revising intuitions about wrongness in the cases, or introducing alternative accounts of harm or value.

5. Parfit’s Central Thought Experiments

Parfit’s most influential presentation of the Non-Identity Problem relies on a small set of stylized cases designed to isolate the key moral intuitions.

The 14-Year-Old Girl

A fourteen‑year‑old chooses to have a child now rather than waiting until she is older and better prepared. Because of the change in conception timing, the child conceived now is a different child from the one she would have had later. The actual child will have a difficult life but one that is still judged worth living. Many think the teenager’s decision is morally criticizable, yet it does not appear to harm that particular child, who would otherwise never have existed.

The Depletion and Conservation Cases

Parfit contrasts two long-term environmental policies:

• Depletion: The present generation uses resources lavishly, increasing its own wellbeing while leaving fewer resources and a harsher environment for future people.
• Conservation: Resources are used more sparingly, making things slightly worse for the present but much better for future generations.

Because different policies affect economic and social conditions, they change patterns of relationships, conceptions, and births. Over time, the set of individuals who exist under Depletion diverges entirely from those who would exist under Conservation. Still, many judge Depletion to be morally worse or wrong.

Pollution and Risk Cases

Parfit also discusses policies that introduce long-term pollution or other risks. The harms (e.g., chronic illness) occur far in the future and afflict individuals whose very existence depends on the polluting policy. Again, those affected cannot claim that, had the policy been different, they would have fared better; they simply would never have existed.

Function of the Experiments

These thought experiments are crafted to:

• Ensure that each actual person’s life is worth living.
• Make clear that the identity of future individuals depends on the choices in question.
• Elicit the sense that some options are morally objectionable despite the absence of straightforward comparative harm.

They have become standard reference points for exploring variations, testing theories, and illustrating the structure of non-identity reasoning.

6. Logical Structure and Underlying Assumptions

Analyses of the Non-Identity Problem typically present it as an argument whose force depends on several explicit and implicit assumptions.

Core Logical Structure

A common reconstruction uses steps like the following:

1. Person-Affecting Principle: An action is wrong only if it is worse for, or harms, some particular person.
2. Identity-Affecting Premise: In many future-regarding or reproductive choices, different options lead to the existence of different individuals.
3. Comparative Harm Assumption: A person is harmed only if they are worse off than they would have been had another feasible option been chosen.
4. Life-Worth-Living Assumption: The individuals brought into existence by the problematic action have lives that, overall, are worth living.
5. No-Harm Conclusion: Therefore, these actions harm no particular person.
6. Wrongness Intuition: Nevertheless, many judge that some such actions are morally wrong or at least clearly worse choices.

The Non-Identity Problem arises from the apparent inconsistency between the person-affecting principle (together with the other assumptions) and the intuition of wrongness.

Key Assumptions

Philosophers identify several crucial assumptions:

Some critics challenge these assumptions directly (e.g., rejecting a purely comparative notion of harm), while others accept the assumptions but revise the moral verdict (e.g., denying that the acts are wrong).

The logical role of the Non-Identity Problem in moral theory is thus largely diagnostic: it tests which assumptions a theory must modify to account for common judgments about future-affecting actions.

7. Person-Affecting Views and Harm-Based Morality

The Non-Identity Problem is often framed as a challenge to person‑affecting and harm‑based approaches, which hold that moral evaluation should focus primarily or exclusively on how actions affect particular individuals.

Person-Affecting Views

Person‑affecting views, in a broad sense, claim that:

• What fundamentally matters morally is making people better or worse off.
• An outcome is better only if it is better for someone.
• Creating additional happy people is not, by itself, a moral improvement unless it benefits some individual.

These views are sometimes motivated by intuitions about respect for persons, or by skepticism about impersonal values that go beyond individual welfare.

Harm-Based Morality

A related but not identical idea is harm-based morality, which links wrongness closely to harm:

• An act is wrong (at least pro tanto) if it harms someone—typically understood in a comparative sense.
• If no one is made worse off than they otherwise would have been, the act is generally permissible, or at least not wrong for harm-based reasons.

The Non-Identity Problem presses on the combination of:

• A person-affecting orientation, and
• A comparative definition of harm.

In non-identity cases, each actual person is not worse off than they would otherwise have been, since the alternative was non-existence. Thus, strictly person-affecting, harm-based views seem to classify certain controversial actions—like the teenager’s decision in Parfit’s case or unsustainable policies—as morally permissible.

Some philosophers embrace this implication, suggesting that our initial judgments about wrongness in such cases are mistaken or overstated. Others see the tension as a reason to revise either the person-affecting focus, the account of harm, or the link between harm and wrongness.

8. Same-Number vs Different-Number Cases

A key structural distinction in population ethics—central to understanding the Non-Identity Problem—is between same-number and different-number cases.

Definitions

Parfit’s core non-identity examples are different-number cases: switching options changes who will be conceived and therefore who exists.

Moral Significance of the Distinction

Philosophers argue that moral principles may legitimately treat these cases differently:

• In same-number cases, comparative, person-affecting judgments seem straightforward: one can ask whether this person would be better or worse off under another option.
• In different-number cases, such pairwise comparisons typically fail, since the individuals in one outcome have no counterpart in the alternative.

Some theorists propose:

• Restricting strong person-affecting constraints and rights to same-number cases.
• Allowing impersonal or aggregative principles to govern different-number cases.

Others question whether the boundary is always clear. Real-world policy decisions may involve both elements: some individuals exist regardless of the choice, while others exist only under certain options. This has led to exploration of mixed or variable-number cases.

The same-number/different-number distinction is thus used to diagnose where non-identity pressures arise most forcefully and to guide the development of theories that apply different evaluative principles depending on whether identity is held fixed.

9. Key Variations and Extensions of the Problem

After Parfit’s original presentation, philosophers developed numerous variants of non-identity scenarios to probe different moral and conceptual dimensions.

Varying the Severity of Outcomes

Some cases focus on severe disability or illness: parents knowingly conceive a child who will suffer from a serious but compatible-with-life condition, when they could have waited to conceive a different, healthier child. This intensifies the intuition that something morally problematic occurs, even when the child’s life is still judged worth living.

Policy vs Individual Choice

Non-identity problems have been extended from individual reproductive decisions to:

• Public health measures (e.g., whether to implement a vaccine program that will influence who survives and reproduces).
• Economic policies that alter social structures and thus affect future conception patterns.
• Climate and environmental policies with long temporal horizons.

These elaborations explore how identity-affecting features operate at population scale.

Risk and Uncertainty

Another line of variation emphasizes risk rather than guaranteed outcomes. For instance, an action may significantly increase the risk that some future people will have very poor lives, though we cannot identify which individuals in advance. These cases test how the Non-Identity Problem interacts with probabilistic harm and expected value.

Temporal and Spatial Extensions

Some discussions push the temporal horizon further, considering extremely distant future populations, or incorporate space colonization scenarios where choices determine not only who lives but where and in what kinds of environments.

Legal and Ethical Extensions

In law and bioethics, non-identity issues have been linked to:

• Wrongful life and wrongful birth suits.
• Debates over genetic enhancement and germline editing, where identity-affecting interventions may be framed as either harmful or beneficial to future persons.

These variations keep the core structure—identity-affecting choices and lives judged worth living—but introduce new features (degree of harm, scale, risk, legal status) to test the robustness of different theoretical responses.

10. Standard Objections and Critical Responses

Philosophers have raised several influential objections to the force or formulation of the Non-Identity Problem. These objections target different components of the argument.

1. Denying the Intuition of Wrongness

Some, such as David Boonin, argue that our intuition that certain non-identity actions are wrong is unreliable. On this view:

• If no one is made worse off in a comparative sense, the action is not wrong (though perhaps regrettable).
• The proper lesson is to revise our moral intuitions, not our theories of harm.

2. Rejecting Purely Comparative Harm

Others challenge the assumption that harm must be comparative. Seana Shiffrin and Elizabeth Harman, among others, suggest:

• A person can be harmed by being brought into existence in a seriously impaired or disadvantaged condition, even if the alternative was non-existence.
• Harm may be non-comparative, tied to objective thresholds or intrinsic features of a state.

This move attempts to restore a harm-based account of wrongness without accepting the non-identity conclusion.

3. Rights-Based and Deontological Critiques

Some theorists contend that Parfit’s framing is too consequentialist and harm-focused. Rights-based and deontological approaches maintain that:

• Individuals can have rights not to be brought into existence under certain conditions.
• Agents may have duties not to engage in certain forms of procreation, regardless of whether anyone is made worse off.

Under this view, wrongness may stem from violated rights or duties, not only from harms.

4. Emphasizing Same-Number vs Different-Number Cases

Another line of criticism, developed by Parfit and others, highlights the distinction between same-number and different-number cases. Some argue:

• Person‑affecting constraints apply only in same-number contexts.
• Different-number cases should be evaluated by other, possibly impersonal, principles.

This reclassification may reduce the apparent paradoxical nature of non-identity scenarios.

5. Questioning the Identity-Dependence Premise

A further response questions the assumption that tiny changes necessarily produce different individuals. Some appeal to alternative views of personal identity or to metaphysical uncertainty, suggesting that identity may not be so sensitive to conception details. This would weaken the claim that many cases are genuinely different-number situations, though this strategy is not widely accepted as a full solution.

These objections shape contemporary debates by indicating which parts of the original Parfitian setup are most controversial and which components different theorists are prepared to modify.

11. Proposed Resolutions and Hybrid Approaches

In response to the Non-Identity Problem, philosophers have advanced a range of proposals, often combining elements from different theoretical traditions.

Impersonal Population Principles

One influential family of responses embraces impersonal evaluation:

• Total or average utilitarianism, for example, judges outcomes by overall wellbeing, regardless of which individuals exist.
• On these views, actions like Depletion are wrong if they lead to states of affairs with lower total or average welfare, even if no specific person is worse off.

This moves away from the strictly person-affecting perspective.

Modified Person-Affecting Views

Some theorists retain a person-affecting core but refine its scope:

• Strong person‑affecting constraints may apply only in same-number cases.
• In different-number cases, supplemental principles—such as “choose the outcome with the best prospects overall” or “avoid creating lives below a certain threshold”—are invoked.

This yields a hybrid or bifurcated moral framework.

Non-Comparative and Threshold Accounts

Another strategy redefines harm or wronging:

• On non‑comparative accounts, bringing someone into existence with very severe disadvantages can be wrong even if non-existence was the only alternative for that individual.
• Threshold or sufficientarian views focus on ensuring that lives meet some standard of “enough” wellbeing; creating lives below that threshold is pro tanto wrong.

These approaches attempt to reconcile harm-based reasoning with the intuition that some non-identity acts are objectionable.

Pluralist and Multi-Level Theories

Several philosophers propose explicitly pluralist theories that:

• Combine person‑affecting constraints, rights, and impersonal values.
• Distinguish between reasons of beneficence, reasons of respect, and reasons of justice.
• Allow that different types of reasons may dominate in different contexts (e.g., reproductive versus policy decisions).

Reinterpretation of Intuitions

A more deflationary strategy holds that:

• Our negative reactions to certain non-identity choices concern agents’ motives, attitudes, or risk imposition, rather than wrongdoing toward particular persons.
• Once this is recognized, the apparent paradox dissipates without major revision to moral theory.

No single proposal commands universal acceptance; instead, the literature features competing and sometimes complementary attempts to accommodate the Non-Identity Problem within broader ethical systems.

12. Implications for Bioethics and Reproductive Decisions

The Non-Identity Problem has become a central reference point in bioethics, especially regarding choices that shape the existence and characteristics of future children.

Genetic Testing and Selection

In prenatal testing, preimplantation genetic diagnosis, and embryo selection, parents and clinicians choose among possible future children:

• Selecting an embryo without a serious genetic condition may result in a different child existing than if another embryo were implanted.
• If a child born with a condition has a life worth living, it is debated whether they have been harmed by being selected, given that the alternative was non-existence.

This complicates claims that certain reproductive decisions are wrong because they harm the resulting child.

“Wrongful Life” and Legal Responsibility

In legal contexts, wrongful life suits involve children alleging that negligent medical advice or testing led to their being born with serious disabilities when they otherwise would not have existed. The Non-Identity Problem raises questions such as:

• Can the child coherently claim they were made worse off?
• Should liability focus instead on harms to parents, or on breached duties that are not strictly harm-based?

Courts and legal theorists differ in how much weight they give to non-identity reasoning.

Reproductive Counseling and Professional Ethics

Genetic counselors and medical professionals often advise prospective parents about risks:

• If conceiving now rather than later will produce a different child, is it ethically problematic to proceed when a later, healthier child could exist?
• Should professionals frame advice in terms of risks to “a future child” generically, or in terms that acknowledge identity-dependence?

The Non-Identity Problem encourages more precise articulation of what it means to “harm” a child in reproductive contexts.

Disability and Expressivist Concerns

Some disability scholars argue that framing certain reproductive choices as wrong (e.g., choosing to conceive a disabled child) risks sending a negative message about existing disabled persons. Non-identity reasoning interacts with these expressivist worries:

• If no particular disabled person is harmed by being brought into existence, criticism of the choice may instead be seen as expressing questionable attitudes toward disability.

Bioethical debates use the Non-Identity Problem both to challenge simple harm-based arguments and to motivate more nuanced accounts of parental responsibility, professional duty, and respect for potential future individuals.

13. Implications for Environmental and Climate Ethics

Environmental and climate policies often have far-reaching, identity-affecting consequences, making them fertile ground for non-identity considerations.

Long-Term Policy and Future Populations

Policies on resource use, emissions, and land management shape:

• Economic conditions,
• Migration patterns,
• Social structures,

which in turn influence who meets whom and when children are conceived. Over time, different policy paths yield different populations. Yet many environmental ethicists argue that some policies—such as those leading to extreme climate change—are morally worse.

The Non-Identity Problem challenges:

• Claims that future individuals are harmed by today’s environmentally harmful policies, if their very existence depends on those policies.
• Simple applications of intergenerational justice that assume fixed future populations.

Climate Justice and Responsibility

In climate ethics, questions of responsibility and compensation arise:

• If future climate victims owe their existence to current emissions, can they claim to have been wronged or harmed by present agents?
• How should we justify obligations to reduce emissions or adapt policy if harm-based interpersonal justification falters?

Some theorists respond by invoking:

• Impersonal values (e.g., minimizing total suffering),
• Collective duties not tied to specific harmed individuals,
• Or rights of future generations conceived more abstractly.

Environmental Law and Policy Design

Non-identity issues also appear in environmental law and policy, for example in cost–benefit analyses or constitutional provisions protecting future generations. Policymakers must decide whether:

• To treat future individuals as particular rights holders who could be harmed, or
• To focus on preserving the environment as a public good or as something valuable independently of the identity of its beneficiaries.

The Non-Identity Problem thus pushes environmental and climate ethicists to clarify whether their arguments rest on harm to particular individuals, on impersonal evaluations of outcomes, or on duties regarding the preservation of nature and human prospects more generally.

14. Connections to Theories of Personal Identity

The Non-Identity Problem is intimately connected to how one understands personal identity, especially across possible worlds or alternative histories.

Identity Dependence on Conception Conditions

Standard presentations assume that:

• Which particular person comes into existence depends sensitively on factors such as the exact sperm and egg involved and timing of conception.
• Small changes in circumstances therefore result in a different individual existing.

This assumption dovetails with widely held biological or origin-based criteria for personal identity, according to which an individual’s identity is tied to their particular gametic origins.

Parfit’s Reductionism

Parfit himself is known for a reductionist view of personal identity, holding that what matters in survival is not strict numerical identity but psychological continuity and connectedness. Some commentators have suggested that:

• If what matters morally is psychological continuity rather than identity per se, the Non-Identity Problem may be reframed.
• However, because non-identity cases concern distinct future lives that never overlap, reductionism does not straightforwardly dissolve the problem.

Alternative Identity Theories

Other theories of identity have been explored for their implications:

Most philosophers working on the Non-Identity Problem accept, at least for practical purposes, that the identity of future persons is sensitive to conception details. The main influence of personal identity theory is therefore to clarify the metaphysical underpinnings of non-identity claims, rather than to provide a widely endorsed solution.

15. Ongoing Debates and Open Questions

Contemporary work on the Non-Identity Problem features numerous unresolved issues and active lines of research.

The Status of Person-Affecting Intuitions

There remains disagreement about:

• Whether person‑affecting intuitions (that morality must be about making specific people better or worse off) are ultimately defensible.
• How much weight to give these intuitions when they conflict with other moral considerations, such as impartial beneficence or fairness.

Harm, Benefit, and Non-Existence

Philosophers continue to debate:

• Whether it is coherent to compare existence with non-existence from the standpoint of a person.
• How to model harm and benefit when one of the options is that the individual never exists.

This affects positions on wrongful life, reproductive choices, and population ethics more broadly.

Integration with Broader Ethical Theories

A major open question is how best to integrate responses to non-identity into comprehensive moral theories:

• Can contractualism, rights-based theories, or virtue ethics systematically address identity-affecting cases?
• Do we need new fundamental principles, or can existing theories be modified without major overhaul?

Practical Norms and Policy Guidance

There is ongoing discussion about how, if at all, the Non-Identity Problem should shape policy and professional practice:

• Should legislators and courts rely on non-identity reasoning in assessing liability or rights of future persons?
• How should climate, health, and reproductive policies be justified when harms to specific individuals are difficult to formulate?

Empirical and Interdisciplinary Dimensions

Some researchers explore connections with:

• Empirical moral psychology, investigating how ordinary people respond to non-identity scenarios.
• Economics and decision theory, examining how to model preferences and welfare when choices affect population size and identity.

These inquiries may influence how philosophers assess the relevance of intuitive judgments and institutional constraints.

The field remains active, with no consensus on a single resolution but considerable agreement that non-identity considerations are indispensable in theorizing about future generations.

16. Legacy and Historical Significance

Since the publication of Reasons and Persons, the Non-Identity Problem has become a standard fixture in discussions of moral philosophy, particularly in population ethics, bioethics, and environmental ethics.

Influence on Population Ethics

Parfit’s problem helped catalyze a distinct subfield focused on evaluating states of affairs with varying populations. It interacts with other canonical puzzles, such as:

• The Repugnant Conclusion in total utilitarianism.
• Debates over total vs average welfare measures.
• Questions about the value of creating additional happy lives.

Many contemporary treatments of population ethics treat the Non-Identity Problem as a central test case for proposed theories.

Impact on Applied Ethics

In applied ethics, non-identity reasoning has:

• Shaped debates over reproductive responsibility, genetic interventions, and disability.
• Informed discussions of climate justice and intergenerational equity, especially in international and constitutional law.
• Influenced the framing of children’s rights and parental duties.

It has also prompted reassessment of legal doctrines concerning wrongful life and the standing of future persons.

Methodological Significance

Methodologically, the Non-Identity Problem illustrates:

• The power of carefully constructed thought experiments to reveal tensions in widely held moral assumptions.
• The importance of integrating metaphysical considerations (about identity and existence) into normative theory.

It has served as a bridge between abstract moral philosophy and concrete policy concerns.

Place in 20th–21st Century Philosophy

The problem is often cited as one of the most significant contributions of late 20th‑century analytic ethics, influencing generations of work on:

• The nature of harm, benefit, and wellbeing.
• The moral status of possible and future persons.
• The structure of moral theories that must handle large-scale, long-term choices.

As a result, the Non-Identity Problem is now widely regarded as a canonical puzzle that any comprehensive ethical theory must address, marking its enduring legacy in both theoretical and practical domains of philosophy.