On What Matters
On What Matters is Derek Parfit’s large-scale attempt to explain and unify the foundations of morality. Across three volumes, Parfit argues that there are objective normative truths about reasons, that morality is grounded in what there is decisive reason to do, and that the best forms of Kantianism, rule consequentialism, and contractualism ultimately converge in what he calls the ‘Triple Theory’. He defends a non-metaphysical, non-naturalist cognitivism about reasons (often called “non-realist realism”), rejects subjectivist and desire-based accounts of normativity, and develops detailed treatments of moral principles, personal identity’s irrelevance for what matters, and the rationality of moral motivation. The work combines technical argument, thought experiments, careful engagement with major contemporary figures, and sweeping systematic ambitions about the nature and unity of morality.
At a Glance
- Author
- Derek Parfit
- Composed
- c. 1980–2011 (Volumes 1–2); c. 2011–2017 (Volume 3)
- Language
- English
- Status
- original survives
- •Objective reasons and non-metaphysical normative truths: Parfit maintains that there are irreducibly normative truths about what we have reason to do and what matters that are not analyzable in naturalistic or psychological terms, but which do not require a spooky metaphysics; they are normative truths analogous to mathematical truths—non-natural, non-empirical, but knowable by rational reflection.
- •Rejection of desire-based and subjectivist theories of reasons: Against Humean and subjectivist views, Parfit argues that normative reasons cannot be grounded merely in an agent’s actual or idealized desires; we can have decisive reasons to want or do what we do not in fact want, and desires themselves stand in need of normative assessment by independent standards of what there is most reason to desire.
- •The Triple Theory (convergence of Kantianism, rule consequentialism, and contractualism): Parfit proposes that when suitably formulated, the best versions of Kantian ethics, rule consequentialism, and Scanlonian contractualism converge on the same normative implications. According to the Triple Theory, an act is wrong just when it is disallowed by all principles that no one could reasonably reject, that everyone could rationally will as a universal law, and whose general acceptance would make things go best.
- •Rationality, reasons, and the error of ‘rational egoism’: Parfit argues that rationality is fundamentally about responding correctly to reasons, not about prudential or self-interested coherence. He criticizes rational egoism and time-neutral theories that treat self-interest as uniquely rational, contending that there can be decisive reasons to act morally even when doing so is not in one’s self-interest, and that rationality can require self-sacrifice when morality requires it.
- •What matters and the irrelevance of personal identity: Extending themes from Reasons and Persons, Parfit contends that the metaphysical fact of personal identity is often ‘empty’ for practical purposes; what matters are psychological continuity and connectedness and various impersonal values. In On What Matters, this underpins his claim that morality and impartial reasons can override narrow concern for the self, since the moral point of view tracks what really matters, not merely prudential continuity.
On What Matters has become a central reference point in contemporary ethics, metaethics, and the theory of reasons. It reshaped debates about the nature of normativity, catalyzed a wave of work on reasons and rationality, and reinvigorated discussions of Kantianism, consequentialism, and contractualism. Parfit’s defense of objective normative truths without heavy metaphysics has influenced many non-naturalist and ‘quietist’ realists; his critique of desire-based theories helped shift the mainstream toward objectivist accounts of reasons; and his Triple Theory has become a touchstone in discussions of theoretical convergence in ethics. The work consolidates Parfit’s standing—alongside figures such as Rawls, Scanlon, and Williams—as one of the defining moral philosophers of the late 20th and early 21st centuries.
1. Introduction
On What Matters is a three-volume work in normative ethics and metaethics by Derek Parfit, published between 2011 and 2017. It aims to answer two tightly connected questions: what we have reason to do and believe, and what, if anything, ultimately matters in human life. Parfit develops a systematic account of normative reasons, of rationality as responsiveness to such reasons, and of moral rightness understood through the convergence of leading moral theories.
The work is notable for both its scope and its integrative ambition. Parfit defends a realist view on which there are objective truths about reasons and morality, while attempting to reconcile three major traditions in moral philosophy: Kantian ethics, consequentialism, and contractualism. He presents a “Triple Theory” which, on his formulation, unifies the best versions of these traditions in a single criterion of wrongness.
Throughout, Parfit’s arguments are intertwined with critical engagement with contemporary philosophers. Much of the text consists of detailed responses to specific objections, revisions of his own earlier views, and constructive reinterpretations of rival approaches. The work therefore functions both as a standalone theory and as a central node in late 20th- and early 21st‑century analytic moral philosophy.
Because of its length and complexity, On What Matters is often approached by parts: some readers focus on its theory of reasons and rationality, others on its treatment of moral theories, and others on its metaethical defense of non-naturalist realism. The entry’s subsequent sections treat these components separately while indicating how Parfit connects them within a single project.
2. Historical and Intellectual Context
Parfit’s project emerges against the backdrop of post‑war analytic ethics, in which metaethics, normative theory, and rational choice theory had often been pursued separately. On What Matters re‑integrates these strands, drawing on earlier debates while responding to late‑20th‑century developments.
Post‑Moorean Metaethics and the Queerness Challenge
After G. E. Moore’s non-naturalist intuitionism, mid‑century emotivism and prescriptivism questioned the cognitive status of moral judgments. J. L. Mackie’s 1977 “queerness” argument framed robust moral realism as metaphysically and epistemologically suspect. Parfit’s non-naturalist realism is formulated in direct dialogue with this tradition and with later expressivist and quasi‑realist accounts.
Normative Ethics: From Theories in Competition to Plural Debates
By the late 20th century, Kantian ethics, consequentialism, and contractualism had typically been treated as mutually exclusive rivals:
| Tradition | Representative late 20th‑c. figures |
|---|---|
| Kantian ethics | Christine Korsgaard, Onora O’Neill |
| Consequentialism | Peter Singer, J. J. C. Smart |
| Contractualism | T. M. Scanlon |
Parfit inherits this tripartite landscape, but proposes that, suitably interpreted, these traditions may systematically converge in their practical verdicts.
Reasons and Rationality in Late 20th‑Century Philosophy
From the 1970s onwards, “reasons” became a central unit of analysis in practical philosophy, influenced by Bernard Williams, John Rawls, and others. Debates arose between subjectivists, who tied reasons to agents’ desires or motivational sets, and objectivists, who grounded reasons in values or facts independent of desire. Parfit’s reasons‑first framework positions him within this objectivist camp, though with significant internal distinctions.
Contemporary Interlocutors
The circulating drafts of On What Matters interacted with work by T. M. Scanlon, Thomas Nagel, Allan Gibbard, Christine Korsgaard, Susan Wolf, Philip Pettit, and many others. Volume 3 explicitly embeds the book within an ongoing exchange, illustrating a shift toward collaborative and dialogical methodology in analytic ethics.
3. Author and Composition History
Derek Parfit’s Background
Derek Parfit (1942–2017) was a British philosopher primarily associated with All Souls College, Oxford. Trained in history before turning to philosophy, he became known for work on personal identity, rationality, and ethics. His earlier book Reasons and Persons (1984) significantly shaped later analytic moral philosophy and laid foundations for On What Matters.
Genesis of the Project
Parfit began developing the ideas that would become On What Matters in the 1980s. Early versions of some arguments appeared in influential articles, while extensive draft chapters circulated privately under titles such as “Climbing the Mountain.” Over time, these drafts were revised in response to comments from a wide circle of philosophers.
| Phase | Approx. dates | Features |
|---|---|---|
| Initial development | 1980s–early 1990s | Early drafts on reasons and moral theory |
| Expanded manuscript | mid‑1990s–2000s | Circulating “Parfit book” among specialists |
| Finalization Vol. 1–2 | late 2000s–2011 | Structured as two volumes; OUP publication |
| Response and revision | 2011–2016 | Replies to critics; substantial reworking |
| Volume 3 publication | 2017 | Revised positions and new clarifications |
Collaboration and Commentaries
A distinctive aspect of the composition history is the systematic incorporation of others’ responses. Essays collected in Samuel Scheffler’s Reason and Value (2004) and later symposia on the draft manuscript fed into Parfit’s revisions. Volume 3, together with a companion volume of critical essays, documents this iterative process.
Relation to Reasons and Persons
Many commentators view On What Matters as a sequel to Reasons and Persons. While the earlier book focused on personal identity, rationality, and population ethics, it already gestured toward objectivist views of reasons and possible convergence in moral theory. On What Matters develops these glimpses into a comprehensive treatment of reasons, moral theories, and metaethics.
Parfit continued revising material almost until his death, and some scholars suggest that even the published volumes represent only one snapshot in an evolving project.
4. Structure and Organization of On What Matters
Overall Layout
The work is divided into three volumes, each containing multiple parts with relatively self‑standing themes:
| Volume | Main Parts (by topic) |
|---|---|
| 1 | Reasons; Rationality and Normativity; Metaethics; Moral Theories as Theories of Reasons |
| 2 | Kantian Theory; Consequentialism; Contractualism |
| 3 | Replies to Critics; Further Developments; Metaethical Clarifications |
Parfit intends readers to see these volumes as mutually supporting: the account of reasons underpins the account of morality, which in turn motivates his metaethics.
Volume 1: Foundations
Volume 1 begins with a detailed analysis of normative reasons, including the distinction between apparent and real reasons and between object‑given and state‑given reasons. It then considers the nature of rationality, arguing that rational requirements are grounded in reasons rather than mere coherence. A substantial metaethical section defends non‑naturalist realism. The closing part reinterprets Kantianism, consequentialism, and contractualism as competing theories about reasons for acting.
Volume 2: Detailed Treatment of Moral Theories
Volume 2 devotes separate parts to:
- A reconstructed Kantian ethics centered on universalizable principles.
- A defense and refinement of rule‑consequentialism.
- An interpretation and modification of Scanlonian contractualism.
These parts elaborate the components that will be later unified in the Triple Theory, while responding to traditional objections within each tradition.
Volume 3: Responses and Revisions
Volume 3 gathers Parfit’s replies to critics of both his normative and metaethical positions, and revises aspects of the earlier presentation. He clarifies how moral theories are supposed to converge, refines his understanding of reasons and rationality, and addresses sophisticated metaethical challenges. The volume thus functions as both an extension and a partial correction of Volumes 1 and 2.
5. Reasons, Rationality, and Normativity
A central theme of On What Matters is the analysis of normative reasons and their relation to rationality and normativity more broadly.
Reasons as the Basic Normative Notion
Parfit treats normative reasons as facts that count in favor of actions or attitudes. He distinguishes:
| Type of reason | Characterization |
|---|---|
| Apparent reason | Seems to favor an act, but is based on error or illusion |
| Real reason | Genuinely favors an act, grounded in true facts |
On his view, real reasons are independent of agents’ desires; they are object‑given rather than state‑given, in that they depend on features of actions or outcomes, not on the value of being in certain psychological states.
Proponents of this reasons‑first approach argue that it offers a unified explanation of moral, prudential, and epistemic normativity. Alternative views instead treat values, obligations, or rational requirements as more fundamental.
Rationality as Responding to Reasons
Parfit characterizes rationality as correctly responding to one’s real reasons. He contrasts this with:
- Internalist or coherence views, on which rationality is roughly consistency among beliefs, desires, and intentions.
- Desire‑based accounts, on which rationality is about effective means to given ends.
Parfit’s account implies that someone with coherent but morally abhorrent desires may still be deeply irrational if they fail to respond to strong reasons against their actions.
Other theorists propose different models—such as rationality as coherence, or as responsiveness to one’s own standpoint or identity—and some argue that Parfit’s “reasons fundamentalism” presupposes the very objectivism that is under debate.
Normativity and the Scope of Reasons
Parfit’s framework treats all “oughts” (moral, prudential, epistemic) as ultimately explicable in terms of reasons. He also distinguishes wide value‑based reasons, which leave room for multiple rational options, from narrower reasons that uniquely determine what one rationally ought to do. This distinction is intended to accommodate reasonable pluralism in practical decision‑making while maintaining objectivity, though some critics question whether the line between wide and narrow is stable.
6. Metaethics and Non-Naturalist Realism
In On What Matters, Parfit develops and defends a form of non-naturalist normative realism. This view holds that there are objective normative truths—about reasons, right and wrong, and what matters—that are not reducible to natural or descriptive properties.
Core Commitments of Parfit’s Realism
Parfit’s position combines several theses:
- Cognitivism: Normative judgments purport to state truths.
- Realism: Some such judgments are in fact true, independent of our attitudes.
- Non-naturalism: These truths are not identical to, or reducible to, natural facts such as psychological or sociological states.
He compares normative truths to mathematical or modal truths: irreducible but not thereby mysterious.
Engagement with the Queerness Objection
Mackie’s “queerness” objection held that objective values would be metaphysically and epistemologically strange. Parfit responds by arguing that:
“Normative truths may be irreducible, but they are not, in any objectionable way, queer.”
He suggests that accepting irreducible normative facts is no more problematic than accepting truths about numbers, sets, or possibilities. Critics argue that this analogy may understate normative properties’ purported motivational force or fail to address epistemic access.
Alternatives: Expressivism, Constructivism, and Error Theory
Parfit contrasts his view with several rivals:
| View | Central claim about moral judgments |
|---|---|
| Expressivism | Express non‑cognitive attitudes rather than beliefs |
| Constructivism | Normative truths are constructed from rational agency or procedures |
| Error theory | All moral claims purport to state objective truths but are false |
He argues that expressivist and quasi‑realist accounts struggle to fully vindicate the apparent objectivity of moral disagreement; that constructivist views cannot ground the normativity they presuppose without circularity; and that error theory makes our normative practices unintelligible.
Proponents of these rival positions contend, in turn, that Parfit’s non-naturalism leaves unexplained how we can know normative truths, what role they play in explanation, and how they integrate with a naturalistic worldview.
Epistemology of Normative Truths
Parfit hints at a form of rational intuition or understanding as the route to normative knowledge, likening it to our grasp of mathematical axioms. Supporters see this as capturing the seeming self‑evidence of some moral claims; skeptics question whether such intuitions are reliable or culturally variable, and whether the analogy with mathematics holds.
7. The Triple Theory and Moral Theory Convergence
A distinctive claim of On What Matters is that properly formulated versions of three major moral traditions—Kantian ethics, rule‑consequentialism, and Scanlonian contractualism—converge on the same criterion of wrongness. Parfit labels this result the Triple Theory.
Statement of the Triple Theory
In one canonical formulation, an act is wrong if and only if it is:
disallowed by the principles that (i) everyone could rationally will to be universal laws,
(ii) would be permitted by the rules whose general acceptance would make things go best, and
(iii) no one could reasonably reject.
Parfit argues that refining each tradition in light of objections leads them toward these shared principles.
Convergence as “Climbing the Same Mountain”
Parfit uses the image of different climbers ascending the same mountain from different sides. Kantianism, consequentialism, and contractualism supposedly start from distinct ideas—universal law, making things go best, and reasonable rejection—but, once clarified and corrected, arrive at overlapping practical verdicts about right and wrong.
Supporters of this convergence thesis claim that it explains why diverse moral intuitions and theories often agree in central cases, and suggests a path toward theoretical reconciliation.
Objections to Convergence
Critics raise several concerns:
- Selective reconstruction: Some contend that Parfit achieves convergence only by modifying each theory in ways that abandon core commitments (for example, Kantian emphases on autonomy, or contractualism’s non‑aggregative structure).
- Residual disagreements: Others argue that even on Parfit’s reconstructed versions, deep disagreements remain about issues such as aggregation, agent‑relative permissions, and the weight of special obligations.
- Pluralism vs. unification: An alternative view holds that persistent disagreements indicate genuine moral pluralism rather than a single underlying theory.
Volume 3 revisits the Triple Theory in light of such objections, with Parfit offering clarifications and some softening of the convergence claims while still insisting on significant overlap in practical conclusions among the best versions of the three traditions.
8. Kantian Ethics in On What Matters
Parfit devotes substantial attention to Kantian ethics, especially in Volume 2, Part 5, where he interprets and reconstructs Immanuel Kant’s views for integration into the Triple Theory.
Focus on the Formula of Universal Law
Parfit’s main Kantian focus is the Formula of Universal Law (FUL): act only on maxims that one could will to be a universal law. He distinguishes:
- A test of willability: whether a maxim can be rationally willed as universal.
- A test of consistency: whether willing the maxim’s universalization would undermine the agent’s own ends.
He develops interpretations aiming to avoid familiar problems with rigid or formal readings of the FUL, such as over‑permissiveness or over‑restrictiveness.
Rational Willing and Reasons
Parfit recasts Kantian constraints in his reasons‑first language: a principle is morally acceptable if everyone could rationally will it, given their reasons. This shifts emphasis from pure practical reason in a Kantian sense to facts about what agents have most reason to will.
Some Kantians see this as a faithful elaboration of Kant’s concern with rational universalizability. Others view it as a substantive departure, replacing Kant’s notion of autonomy and the moral law with Parfit’s objectivist theory of reasons.
Relation to Other Kantian Formulas
While the FUL is central, Parfit also discusses Kant’s other formulations, such as the Formula of Humanity, which requires treating persons as ends in themselves. He suggests that respecting persons as ends can be modeled within his broader framework of reasons and value, and that Kantian demands to respect agency largely cohere with rule‑consequentialist and contractualist principles once these are properly specified.
Critics argue that this interpretive strategy may underplay the distinctively deontological aspects of Kantian ethics—such as the non‑instrumental significance of autonomy or the categorical nature of duty—and that Parfit’s version may be closer to a sophisticated consequentialism than to Kant’s original system.
9. Consequentialism and Rule-Consequentialism
Parfit’s treatment of consequentialism in On What Matters centers on a defense and refinement of rule‑consequentialism in Volume 2, Part 6.
From Act- to Rule-Consequentialism
Parfit distinguishes:
| View | Basic idea |
|---|---|
| Act‑consequentialism | Right acts maximize value in each situation |
| Rule‑consequentialism | Right acts conform to rules whose general acceptance would make things go best |
He argues that simple act‑consequentialism faces familiar objections concerning demandingness, unfairness, and disregard for rights or integrity. Rule‑consequentialism, by evaluating rules rather than individual acts, is presented as able to accommodate constraints and permissions while retaining a broadly consequentialist structure.
Rules Whose Acceptance Makes Things Go Best
On Parfit’s formulation, the correct moral principles are those whose general acceptance would lead to outcomes that are, in some suitably broad sense, best. This incorporates:
- Constraints against harming or violating rights, justified by their role in producing better overall patterns when widely followed.
- Permissions that allow agents some freedom to favor their own projects, again defended by the long‑run benefits of such latitude.
Supporters of this approach claim that it captures many common‑sense moral intuitions while preserving a single, outcome‑based rationale.
Challenges and Alternative Consequentialisms
Critics raise several issues:
- Collapse concerns: Some argue that rule‑consequentialism either collapses into act‑consequentialism or yields rules that are themselves act‑consequentialist in disguise.
- Rule worship: Others suggest that sticking to rules even when breaking them would improve outcomes is irrational from a consequentialist perspective.
- Aggregation disputes: Some object to the aggregative structure of consequentialism itself, which Parfit largely retains.
There are also rival forms of consequentialism—such as scalar, satisficing, or agent‑relative versions—that Parfit discusses but does not adopt. His preferred version is designed to mesh with Kantian and contractualist elements in the Triple Theory, emphasizing the role of principles that could be publicly accepted and internalized.
10. Contractualism, Scanlon, and Reasonable Rejection
Volume 2, Part 7 of On What Matters engages with contractualism, focusing on T. M. Scanlon’s influential formulation in What We Owe to Each Other.
Scanlonian Contractualism
Scanlon proposes that an act is wrong if it would be disallowed by any set of principles that no one could reasonably reject. Reasonable rejection is based on individuals’ complaints about the burdens imposed on them, taking into account others’ competing claims.
Parfit accepts much of this structure but develops several clarifications and revisions to fit it into his broader framework of reasons.
Interpreting “Reasonable Rejection”
A central issue is how to understand reasonable rejection:
- Scanlon emphasizes a non‑aggregative, individualist picture of complaints.
- Parfit argues that, in practice, contractualist reasoning must recognize some forms of aggregation, especially in cases involving many small harms.
He recasts reasonable rejection in terms of reasons individuals have to reject certain principles and whether these reasons are stronger than competing reasons others have to accept them. This reinterpretation is intended to bring contractualism into closer alignment with his objectivist reasons‑first theory.
Contractualism in the Triple Theory
Parfit treats contractualism as one “side of the mountain” whose core insight is that morality is structured by principles that could be justified to each person. Within the Triple Theory, contractualist constraints interact with Kantian universalizability and rule‑consequentialist assessments of what would make things go best.
Supporters of Parfit’s reinterpretation suggest that it illuminates the underlying unity between justifiability and outcome‑based concerns. Critics contend that the move toward aggregation and value‑based reasons dilutes the distinctiveness of Scanlon’s contractualism, which is often seen as resisting straightforward aggregation of complaints.
Some contractualists also question whether Parfit’s revisions preserve the interpersonal justification at the heart of Scanlon’s view, or whether they shift the focus to impersonal value.
11. Key Concepts and Technical Terminology
On What Matters introduces and systematizes a number of technical terms. Several central notions already outlined in this entry’s glossary play specific roles within Parfit’s arguments.
Reasons-Related Distinctions
- Normative reason: A fact that counts in favor of an action or attitude.
- Apparent vs. real reasons: Apparent reasons seem to favor an action but are grounded in error; real reasons are grounded in true facts.
- Object‑given vs. state‑given reasons: Object‑given reasons concern the object of an attitude (e.g., the truth of a belief); state‑given reasons concern the value of being in a state (e.g., the comfort of believing something). Parfit questions whether state‑given considerations are genuine reasons for belief.
Rationality and Value
- Rationality as responding to reasons: Rational agents correctly respond to their real reasons, not merely by harmonizing their desires or beliefs.
- Wide vs. narrow value‑based views: On wide views, multiple responses to value can be rationally permissible; on narrow views, there is typically one uniquely rational response.
Moral-Theoretic Concepts
- Triple Theory: The proposed convergence of refined Kantian, rule‑consequentialist, and contractualist principles.
- Rule‑consequentialism: Rightness determined by conformity to rules whose general acceptance would make things go best.
- Kantian contractualism: Parfit’s hybrid label for principles that everyone could rationally will and could not reasonably reject.
Metaethical Terms
- Non-naturalist normative realism: The thesis that there are irreducible, objective normative truths not reducible to natural facts.
- Agential subjectivism: Views that ground reasons in an agent’s desires or motivational set.
- Queerness objection: Mackie’s challenge that objective moral properties would be metaphysically and epistemologically “queer.”
These terms provide the vocabulary through which Parfit articulates his views on reasons, rationality, and moral theory, and they recur across the three volumes in varying configurations.
12. Famous Passages, Analogies, and Illustrative Cases
Parfit is known for deploying vivid images and stylized cases to make abstract points in On What Matters.
Climbing the Same Mountain
Perhaps the most cited analogy depicts moral theorists as climbers:
We can compare these three theories to climbers who have started from different sides of a mountain.
— Parfit, On What Matters, Vol. 1
The image is used to convey the idea that Kantian ethics, rule‑consequentialism, and contractualism may converge on the same moral truths, despite starting from distinct foundations.
Apparent vs. Real Reasons
Parfit often illustrates the difference between apparent and real reasons with cases involving mistaken beliefs—for instance, a person who drinks from a glass they believe contains water but which in fact contains poison. The fact that the drink seems refreshing is only an apparent reason; the fact that it is poisonous is the real reason not to drink.
Aggregation and Harms
While some of the most famous “Harmless Torturers” style cases appear in Reasons and Persons, On What Matters uses analogous scenarios to discuss issues of aggregation: for example, comparing a large number of minor harms to a smaller number of serious harms, in order to test contractualist and consequentialist principles about when many small complaints can together outweigh a few large ones.
Wide Value-Based Reasons
To explain wide value‑based reasons, Parfit uses examples such as choosing between several worthwhile projects or careers, none of which is uniquely rationally required. These cases illustrate his claim that rationality often permits a range of options, all supported by sufficient reasons.
These passages and examples serve as touchstones in the secondary literature, frequently cited when discussing Parfit’s convergence thesis, his theory of reasons, and his treatment of aggregation.
13. Philosophical Method and Style
Parfit’s method and style in On What Matters are distinctive and have themselves attracted commentary.
Reasons-First and Case-Based Argument
Methodologically, Parfit starts from intuitive judgments about cases and from claims about reasons, treating these as more secure than abstract theoretical principles. He frequently:
- Constructs detailed hypothetical scenarios.
- Tests competing theories by their implications for these cases.
- Revises or refines theories to better align with considered judgments.
This approach reflects a broadly reflective-equilibrium style, though centered on reasons rather than raw intuitions or principles.
Dialogical and Interlocutor-Focused Structure
Large portions of the book are framed as direct engagement with named philosophers. Parfit quotes, paraphrases, and then responds to objections from Allan Gibbard, T. M. Scanlon, Christine Korsgaard, and many others. Volume 3 intensifies this dialogical structure, sometimes presenting long sequences of objection and reply.
Supporters see this as exemplifying philosophy as a collaborative enterprise; critics suggest it can make the text difficult to follow for readers not already familiar with the background debates.
Expository Style
Parfit’s prose is generally clear and unadorned but highly repetitive and incremental. He often:
- States theses in multiple formulations.
- Uses numbered points and fine‑grained distinctions.
- Revisits earlier claims later with modifications.
This style aims at precision and transparency but contributes to the work’s length and density. Some readers find it exceptionally rigorous; others view it as overwhelming.
Reliance on Analogies and Comparisons
As noted, Parfit frequently uses analogies (e.g., mountains, mathematical truths) to clarify abstract claims, especially in metaethics. The comparison between normative truths and mathematical or modal truths is an example, intended to render non‑naturalism more intuitive.
Overall, his method combines analytic rigor, case-based testing, and extensive engagement with contemporary literature, producing a work that functions both as original theory and as extended commentary on the state of moral philosophy.
14. Critical Reception and Major Debates
Upon publication, On What Matters was widely regarded as a landmark in analytic moral philosophy, but it also sparked extensive debate across several dimensions.
Reception Overview
Many reviewers praised the work’s ambition, argumentative care, and breadth of engagement. It quickly became central in discussions of reasons, moral realism, and the relationship between leading moral theories. At the same time, concerns were raised about its length, complexity, and the accessibility of some arguments.
Major Points of Contention
Key debates include:
| Issue | Main lines of debate |
|---|---|
| Convergence/Triple Theory | Whether Kantianism, consequentialism, and contractualism genuinely converge or are artificially reconstructed. |
| Non-naturalist realism | Whether Parfit’s irreducible normative truths are metaphysically and epistemologically acceptable. |
| Reasons fundamentalism | Whether reasons are the basic normative unit, or whether values, requirements, or practical identities are prior. |
| Rationality account | Whether rationality is best understood as responding to reasons rather than as coherence or standpoint-relative justification. |
| Aggregation and persons | How Parfit’s approach handles aggregation of harms and distributive concerns, especially within contractualism. |
Representative Critiques
- Some Kantians and contractualists argue that Parfit’s reconstructions misrepresent their traditions, smoothing over genuine disagreements about autonomy, respect, or the non‑aggregative structure of moral justification.
- Metaethicists sympathetic to naturalism or expressivism contend that Parfit’s comparison of normative truths to mathematical truths does not resolve worries about queerness or epistemic access.
- Others question whether his reasons‑first framework covertly assumes objectivism and thereby begs key questions against subjectivist or constructivist rivals.
Volume 3 responds to many of these critiques, leading to further debate about how much Parfit’s positions changed and whether his replies succeed. The book continues to generate discussion not only about its specific theses but about methodology in moral philosophy more generally.
15. Legacy and Historical Significance
On What Matters has come to be seen as a major work of late 20th- and early 21st‑century moral philosophy, influencing both substantive debates and methodological approaches.
Impact on Normative Ethics
The book reshaped discussions of the relationships among Kantian ethics, consequentialism, and contractualism. Whether or not philosophers accept Parfit’s convergence thesis, it has become standard to consider how these theories interact, overlap, or might be reconciled. The idea that major moral theories might be “climbing the same mountain” has become a reference point in teaching and research.
Influence on Metaethics and Reasons Theory
Parfit’s detailed defense of non‑naturalist normative realism has contributed to a resurgence of interest in robust moral realism. His reasons‑first framework has helped cement reasons as a central concept in practical philosophy, informing later work by T. M. Scanlon, Ralph Wedgwood, Michael Smith, and many others.
Debates over object‑given versus state‑given reasons, wide value‑based rationality, and the nature of normative explanation often take On What Matters as a key starting point.
Methodological Legacy
The work also exemplifies a collaborative, interlocutor‑focused model of philosophy. Its extensive engagement with contemporary critics, especially in Volume 3, has encouraged more dialogical and symposia‑driven practices in analytic ethics. Some see it as a model of large‑scale, integrative theorizing; others as illustrating the challenges of such ambitious projects.
Place in Parfit’s Oeuvre and in the Canon
Together with Reasons and Persons, On What Matters has secured Parfit’s place as a central figure in modern analytic philosophy. The two works are often studied in tandem, with the latter viewed as extending and systematizing themes from the former. In many graduate programs and advanced undergraduate courses, parts of On What Matters now function as canonical readings on reasons, realism, and moral theory.
The book’s long‑term significance continues to develop as new generations of philosophers engage with its arguments, refine its distinctions, and contest its conclusions.
Study Guide
advancedOn What Matters is long, dense, and assumes familiarity with contemporary analytic ethics and metaethics. The arguments frequently presuppose background debates and proceed via fine-grained distinctions. Advanced undergraduates with a strong philosophy background and graduate students are the primary audience; motivated readers should approach selectively and with secondary support.
Objective reasons
Normative considerations—typically facts—that count in favor of actions or attitudes independently of an agent’s actual desires, preferences, or beliefs.
Triple Theory
Parfit’s claim that the best, suitably revised forms of Kantian ethics, rule consequentialism, and Scanlonian contractualism converge on the same principles of right and wrong: an act is wrong iff it is disallowed by principles that (a) everyone could rationally will, (b) whose general acceptance would make things go best, and (c) no one could reasonably reject.
Rule consequentialism
A form of consequentialism that evaluates moral rules by the goodness of the outcomes that would result from their general acceptance, and holds that actions are right when they conform to the best such rules.
Contractualism and reasonable rejection
Contractualism (in Scanlon’s form) assesses right and wrong in terms of principles that no one could reasonably reject; a principle is reasonably rejectable if some person has sufficient grounds, from her standpoint, to reject its being generally accepted.
Kantian universal law
The Kantian idea—via the Formula of Universal Law—that an action is wrong if its maxim could not be willed as a universal law by all rational agents without contradiction or undermining their own ends.
Non-naturalist realism about normativity
The view that there are irreducibly normative truths (about reasons, right and wrong, what matters) that are not identical to or reducible to natural or psychological facts, but are nonetheless objective and knowable.
Rational egoism vs. rationality as responding to reasons
Rational egoism claims that it is always rational to act in one’s own self-interest and irrational not to; Parfit instead defines rationality as correctly responding to objective reasons, which may require impartiality and self-sacrifice.
Climbing the same mountain
Parfit’s metaphor for his convergence thesis: Kantianism, rule consequentialism, and contractualism are like climbers ascending the same mountain from different sides, approaching the same moral truths from distinct starting-points.
How does Parfit’s distinction between apparent and real reasons support his rejection of desire-based (Humean) theories of reasons?
In what ways does Parfit’s non-naturalist realism attempt to avoid Mackie’s ‘queerness’ objection, and how convincing is the analogy with mathematical truths?
Does Parfit’s reconstruction of Kantian ethics preserve what is distinctively Kantian, or does it transform Kant into a sophisticated consequentialist?
Can rule-consequentialism, as presented by Parfit, avoid both the ‘collapse into act-consequentialism’ and ‘rule worship’ objections?
Is Parfit’s introduction of aggregation into contractualism compatible with Scanlon’s idea that moral justification must be addressed to each person individually?
To what extent does the Triple Theory genuinely reveal deep unity among Kantianism, consequentialism, and contractualism, rather than simply overlapping verdicts in a range of central cases?
How does Parfit’s view that rationality consists in responding correctly to objective reasons challenge the idea that rational egoism is obviously true?
What methodological lessons about doing moral philosophy can be drawn from Parfit’s case-based, interlocutor-focused, and highly collaborative style in On What Matters?
How to Cite This Entry
Use these citation formats to reference this work entry in your academic work. Click the copy button to copy the citation to your clipboard.
Philopedia. (2025). on-what-matters. Philopedia. https://philopedia.com/works/on-what-matters/
"on-what-matters." Philopedia, 2025, https://philopedia.com/works/on-what-matters/.
Philopedia. "on-what-matters." Philopedia. Accessed December 11, 2025. https://philopedia.com/works/on-what-matters/.
@online{philopedia_on_what_matters,
title = {on-what-matters},
author = {Philopedia},
year = {2025},
url = {https://philopedia.com/works/on-what-matters/},
urldate = {December 11, 2025}
}