Derek Parfit
Reasons and Persons — personal identity is not what matters; ethics is what we have most reason to do
"Reasons and Persons" (1984) is one of the most influential analytic-philosophy books of the late twentieth century. Parfit argued that personal identity over time is not "what matters" in survival — what matters is psychological continuity with one's future self, regardless of strict identity. This bears directly on ethics: if my future self is partly a "different person," my self-interested reasons to care about that future are weaker than we thought, and the gap between prudence and morality narrows. The two-volume "On What Matters" (2011, with a third volume in 2017) attempted to show that the three principal Western ethical traditions (Kantian, consequentialist, contractualist) converge on a single ethical truth — the "Triple Theory." Parfit lived austerely at All Souls and published rarely but to great effect.
Key works
- Reasons and Persons (1984)
- On What Matters (vols. I-II, 2011; vol. III, 2017)
Declared Influences
Analytic Metaphysics / Logical Atomism 30%
Kantian Transcendental Idealism 20%
Pragmatism 10%
Buddhism 15%
Naturalism 15%
Parfit's analysis of personal identity is one of the principal late-twentieth-century achievements of analytic metaphysics; his work shaped a generation of work on persons, time, and ethics.
"Personal identity is not what matters in survival; what matters is psychological continuity." (Reasons and Persons III)
Parfit's mature ethics in On What Matters takes Kantian ethics as one of the three converging traditions; his project was to show that Kant's contractualism, Sidgwick's consequentialism, and Scanlon's contractualism arrive at the same destination.
"Kantian, consequentialist, and contractualist theories are climbing the same mountain from different sides." (On What Matters I)
Parfit's consequentialist sympathies and his practical-ethics focus on what we have most reason to do has affinities with pragmatist ethical thinking, though he was not formally a pragmatist.
"What we have most reason to do depends on what makes our lives go well and what we owe to others." (On What Matters II)
Parfit himself drew the parallel between his reductionist account of personal identity and Buddhist anatman — there is no enduring self; what we call "person" is a stream of psychological connections.
"My view is one that Buddha and Hume would have welcomed. It implies that no person endures." (Reasons and Persons IV)
Parfit's framework is metaphysically naturalist — persons are physical-psychological systems, identity is reducible to underlying continuities — even where his ethics resists reductionism.
"Persons exist, but in a less deep way than we thought." (Reasons and Persons III)
Internal Tensions
Parfit's "Triple Theory" — that Kantian, consequentialist, and contractualist ethics converge — was contested even by his closest interlocutors (Scanlon's reply in OWM volume II is friendly but skeptical). The austerity of his life and the singular intensity of his philosophical commitments produced both his major contributions and the perception that he had narrowed the field of moral philosophy too sharply.
I. Time
Standard linear physical time; the question of identity over time is the central problem.
Attributes
II. Space
Standard substantival space.
Attributes
III. Matter
Standard substantival matter; persons are reducible to brains-and-bodies in psychological continuity.
Attributes
IV. Observer
Plural psychologically-continuous person-stages. Mediated knowledge through inference. No metaphysical agency.
Attributes
V. Energy
Standard physics.
Attributes
VI. Information
Information not personally conserved beyond death; identity is a matter of degree.
Attributes
Classified works
Works in the atlas that Derek Parfit authored or that draw on this persona's writings, with full attribute fingerprints of their own.
Computed school proximity
The persona's attribute fingerprint scored against all 202 schools using the same quiz scorer. Useful as a sanity check on the hand-curated influences above.
Philosophical neighbors
Other personas whose attribute fingerprint sits closest to Derek Parfit's — intellectual neighbors across traditions and eras.
How Derek Parfit resolves each dilemma
57 resolved positions across 4 dimensions, including 4 distinctive where the majority of schools go the other way.
Each dimension is sorted so minority positions come first. Mainstream positions are folded into an expandable list.
Time · 9 dilemmas · 3 distinctive
Persistence, the future, and the direction of becoming.
6 mainstream positions
Matter · 7 dilemmas, all mainstream
Observer · 37 dilemmas · 1 distinctive
Mind, agency, and the knower's relation to the known.
36 mainstream positions
Information · 4 dilemmas, all mainstream
Films Referencing This Persona (8)
Either directly referenced in the film, or reading the film through one of this persona's top schools.
Experiments Engaging This Persona's Schools
Surface via influence-schools that respond to the experiment. Each entry shows the school through which the connection runs.