Philosophical Concepts
A glossary of key concepts from the world's philosophical traditions — Greek, modern Western, German, analytic, Indian, Chinese, and Buddhist — with definitions, intellectual history, and links to the philosophers most associated with each. Use the entries to follow a concept across thinkers and traditions.
Ancient Greek
- Akrasia The Greek term for weakness of will — acting against one's better judgment — and the central problem of moral psychology since Plato's Protagoras.
- Allegory of the Cave Plato's image in Republic Book VII of prisoners chained in a cave who mistake shadows for reality — and the philosopher's painful ascent into the light.
- Aporia The Greek term for an impasse in inquiry — the productive puzzlement Socrates leaves his interlocutors in by exposing the contradictions in what they took themselves to know.
- Eudaimonia Aristotle's term for the highest human good, usually translated as flourishing — the activity of the soul in accordance with virtue across a complete life.
- Logos A central Greek philosophical term meaning word, reason, or rational principle — used by Heraclitus, the Stoics, and the early Christians for the order underlying the cosmos.
- Mimesis The Greek term for imitation or representation — central to Plato's critique and Aristotle's defense of poetry, painting, and the arts.
- Telos The Greek term for end, goal, or completed purpose — central to Aristotle's account of nature and ethics, and the target of much modern critique.
- Theory of Forms Plato's doctrine that what is most real are eternal, unchanging Forms — Justice, Beauty, the Good — of which sensible things are imperfect images.
Hellenistic
Modern Western
- Categorical Imperative Kant's supreme principle of morality: act only on a maxim you can will as a universal law for all rational agents.
- Cogito Descartes's foundational principle: the existence of the thinking self is indubitable, since to doubt is already to think.
- Free Will The capacity of agents to choose among alternative possibilities — and the central question of whether this capacity is compatible with the causal order of nature.
- Mind-Body Problem The question of how mental states relate to physical states — and whether they are the same kind of thing, two kinds of thing, or something else entirely.
- Monad Leibniz's term for the simple, immaterial, individual substances that constitute reality — windowless atoms of perception that mirror the universe from a unique perspective.
- Occasionalism The doctrine that finite things have no genuine causal power; God is the only true cause, and the apparent interactions of bodies and minds are merely the occasions on which God acts.
- Primary and Secondary Qualities Locke's distinction between qualities that genuinely inhere in objects (extension, motion, figure) and qualities that exist only as effects on perceivers (color, sound, taste).
- Problem of Evil The question of how the existence of suffering and moral wrong can be reconciled with belief in an all-powerful, all-knowing, all-good God.
- Social Contract The doctrine that legitimate political authority is grounded in an agreement among the governed — actual, hypothetical, or rational.
- State of Nature The hypothetical pre-political condition from which social-contract theorists derive the legitimacy and limits of political authority.
- Tabula Rasa Locke's doctrine that the mind at birth is a blank slate, with all ideas derived from sensation or reflection — the founding statement of empiricism.
German Idealism and 19th Century
- Alienation Marx's term for the structural separation of workers under capitalism from their labor, its products, their human nature, and one another.
- Amor Fati Nietzsche's formula for the affirmative attitude of saying yes to one's life as it is — including its suffering — and willing nothing to be otherwise.
- Dialectic A philosophical method of reasoning through opposition and resolution, most associated with Hegel's account of the development of thought and history.
- Eternal Recurrence Nietzsche's thought experiment: if the same life would have to be lived again and again, eternally, would you affirm it?
- Master-Slave Dialectic Hegel's analysis in the Phenomenology of Spirit of the struggle for recognition between two self-consciousnesses, and the unexpected liberatory potential of the bondsman's labor.
- Nihilism The view that there are no objective values, meaning, or purpose — diagnosed by Nietzsche as the decisive crisis of European modernity.
- Ressentiment Nietzsche's term for the reactive psychology of the powerless — the inversion of values by which weakness becomes virtue and strength becomes vice.
- Will to Power Nietzsche's term for the fundamental drive that, on his account, underlies all of life — not only domination but the impulse toward mastery, growth, and self-overcoming.
- Übermensch Nietzsche's figure of the human type capable of creating new values after the death of God — usually translated as overman or higher type.
20th-century Continental
- Bad Faith Sartre's term for the project of denying one's own freedom by treating oneself as a fixed thing rather than as the consciousness one is.
- Dasein Heidegger's term for the kind of being that is at issue for itself — the human being understood as the entity for whom being is a question.
- Panopticon Bentham's prison design taken up by Foucault as the architectural emblem of modern disciplinary power — the visibility through which the subject internalizes its own surveillance.
- Simulacrum Baudrillard's term for the copy without an original — the sign that no longer represents anything but circulates as its own reality.
- The Absurd Camus's term for the confrontation between the human demand for meaning and the silence of a world that does not supply it.
20th-century Analytic
- Falsifiability Popper's criterion for distinguishing science from non-science: a theory counts as scientific only if it forbids some observable state of affairs and is therefore in principle refutable.
- Is-Ought Problem Hume's observation that no purely descriptive premises can entail a normative conclusion — that one cannot derive an ought from an is.
- Naturalistic Fallacy G. E. Moore's charge that ethical naturalists confuse the goodness of a thing with some natural property of it — a fallacy he claimed his open question argument exposes.
- Paradigm Shift Kuhn's term for the discontinuous transition between one scientific framework and its successor — the moment a community changes the conceptual world it inhabits.
- Qualia The subjective, first-person character of experience — the redness of red, the painfulness of pain — and the central problem of contemporary philosophy of mind.
- Trolley Problem The thought experiment, introduced by Philippa Foot and refined by Judith Jarvis Thomson, that asks whether one may divert a runaway trolley to save five people at the cost of killing one.
- Veil of Ignorance Rawls's thought experiment: the principles of justice are those rational agents would choose if they did not know their place in society.
Indian
- Ahimsa The Indian principle of non-violence — the moral discipline of not harming any living being in thought, word, or deed.
- Atman The Hindu term for the innermost self — and, in Advaita Vedanta, identical with Brahman, the ultimate reality.
- Dharma The central Indian concept of cosmic order and right conduct — the proper way of things, the duties owed to one's station, the truth that holds the world together.
- Karma The doctrine, central to Hindu, Buddhist, and Jain philosophy, that intentional actions produce consequences that shape future experience — within and across lifetimes.
- Maya The Hindu concept of cosmic illusion — the apparent multiplicity and substantiality of the world, which conceals the underlying non-dual reality of Brahman.
- Moksha The Hindu term for liberation — release from the cycle of birth and rebirth and the ignorance that sustains it.
- Samsara The Indian concept of the beginningless cycle of birth, death, and rebirth in which all conditioned beings are bound until liberated.
Buddhist
- Anatta The Buddhist doctrine that what we call the self is not a permanent substance but a stream of conditioned mental and physical states.
- Dependent Origination The Buddhist doctrine that all phenomena arise in dependence on conditions — and that the analysis of these conditions is the path to the cessation of suffering.
- Nirvana The Buddhist goal of liberation from the cycle of rebirth — the cessation of craving and the suffering it produces.
- Sunyata The Buddhist doctrine, developed most rigorously by Nagarjuna, that all phenomena are empty of intrinsic nature — they exist only in dependence on conditions.
Chinese
- Dao The way — the central concept of Chinese philosophy, used differently by Daoists and Confucians to name the underlying order according to which things should proceed.
- De The Chinese concept of virtue or moral power — the cultivated character through which a person exerts genuine influence without coercion.
- Li (Ritual Propriety) The Confucian concept of ritual propriety — the cultivated patterns of conduct, ceremony, and social form through which ren is realized in practice.
- Qi The Chinese concept of vital energy or material force — the dynamic substance through which all natural and human phenomena are constituted.
- Ren The central Confucian virtue, usually translated as humaneness — the cultivated disposition to care for others and conduct oneself appropriately within social roles.
- Wu Wei The Daoist principle of acting without forcing — the cultivated capacity to respond to circumstances spontaneously, in accord with the dao.
- Yin and Yang The Chinese cosmological pair denoting complementary, opposing forces whose interplay constitutes all natural and social phenomena.