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
- 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.
- 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.
- 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
- Ataraxia The state of unperturbed tranquility that the Epicureans and Skeptics took as the goal of philosophical life.
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.
- 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.
- 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
- 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.
- 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
- 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.
20th-century Analytic
- 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.
- 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.
- Karma The doctrine, central to Hindu, Buddhist, and Jain philosophy, that intentional actions produce consequences that shape future experience — within and across lifetimes.
- Moksha The Hindu term for liberation — release from the cycle of birth and rebirth and the ignorance that sustains it.
Buddhist
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.
- 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.