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Philosophy's vocabulary is not decoration — it is precision. Each of these words exists because ordinary language could not carry the distinction. Search, or just read: every term is defined the way you would want it explained the first time.
Key philosophical terms include the absurd (our demand for meaning meeting a silent universe), eudaimonia (flourishing through virtue), nihilism (the view that nothing has inherent value), qualia (what experience feels like from inside), and anattā (the Buddhist teaching of no fixed self).
New to the subject? The philosophy meaning & cheat sheet defines the field itself and maps its branches, schools, and eras on one page.
Knowable independently of experience — like mathematics. Contrasted with a posteriori, which requires observation.
Where this lives →Camus' figure who lives fully in spite of meaninglessness — lucid, defiant, without appeal. Sisyphus, pushing, is the archetype.
Where this lives →The philosophy that accepts life has no given meaning and answers with revolt — living fully and lucidly anyway, rather than escaping into suicide or faith.
Where this lives →Weakness of will — knowing the better course and taking the worse one. Socrates doubted it was possible; everyone since has recognised it from the inside.
Where this lives →Love of fate. Nietzsche's demand that we not merely endure what happens but affirm it — to want nothing to be different, forward or back.
Where this lives →The Buddhist teaching of 'no-self': there is no permanent, unchanging essence behind experience — only a process, arising and passing.
Where this lives →Not fear of something specific, but the dizziness of freedom itself — the vertigo of realising nothing prevents you from choosing anything.
Where this lives →The Stoic goal of freedom from destructive passion. Not coldness or numbness, but no longer being dragged around by what you cannot control.
Where this lives →Tranquillity; freedom from disturbance. The aim of the Epicureans and the Sceptics — a mind no longer at war with itself.
Where this lives →Living in accordance with your own freely chosen values rather than inherited scripts or others' expectations.
Where this lives →Sartre's term for lying to yourself about your own freedom — pretending your role, your nature, or your circumstances left you no choice.
Where this lives →Hume's claim that the self is not a thing but a bundle of perceptions in constant flux. Look inward for the 'I' and you find only experiences.
Where this lives →Kant's supreme moral principle: act only on a rule you could will everyone to follow, and treat people always as ends, never merely as means.
Where this lives →'I think, therefore I am.' Descartes' bedrock: the one truth that survives even total doubt, since doubting is itself thinking.
Where this lives →The position that free will and determinism can both be true — freedom means acting from your own desires without external compulsion, not escaping causation.
Where this lives →The fact that there is something it is like to be you. Philosophers dispute nearly everything about it except that it exists.
Where this lives →The family of ethical theories holding that outcomes are what make actions right or wrong. Utilitarianism is its most famous member.
Where this lives →The property of not having to exist. A contingent thing might not have been — which is why 'why is there something rather than nothing?' has teeth.
Where this lives →The Stoic idea that we are citizens of the world before any nation. Diogenes coined it; Marcus Aurelius governed by it.
Where this lives →The Way: the unnameable source and pattern of everything in Taoist thought. The Dao that can be spoken, the classic warns, is not the true Dao.
Where this lives →Ethics grounded in duty and rules rather than outcomes. Some acts are wrong even when they'd produce more good — Kant's central claim.
Where this lives →Pratītyasamutpāda: the Buddhist teaching that everything arises in dependence on conditions — nothing stands alone, including the self.
Where this lives →The view that every event, including every choice, is fixed by prior causes and the laws of nature.
Where this lives →Reasoning that advances through opposition — claim, counter-claim, and a resolution that keeps what survived. Philosophy's engine since Plato.
Where this lives →The Stoic division between what is up to us — our judgments, intentions, responses — and what is not. Peace comes from working only on the first.
Where this lives →The idea that harm foreseen as a side-effect may be permissible, while the same harm used as a means is not. It's why the lever and the footbridge feel different.
Where this lives →Descartes' position that mind and body are two different kinds of thing. Its great problem: how does a non-physical mind move a physical arm?
Where this lives →Usually rendered 'suffering', but closer to unsatisfactoriness — the friction of a life that never quite settles. The First Noble Truth.
Where this lives →The view that knowledge comes primarily from sensory experience. Hume pushed it to its sceptical limit.
Where this lives →The study of knowledge: what it is, how we get it, and how much of what we believe we're actually entitled to.
Where this lives →What makes a thing the thing it is. Existentialism's founding move was to deny humans have one before they act.
Where this lives →Nietzsche's test: could you will your exact life, repeated forever, without editing? Whatever you couldn't affirm is what you haven't yet made peace with.
Where this lives →Aristotle's highest human good, usually translated 'flourishing'. Not a mood but an activity: exercising reason and virtue excellently over a whole life.
Where this lives →Sartre's formula: we are not born with a fixed nature or purpose. We exist first, and make ourselves afterward, through what we do.
Where this lives →Popper's line between science and non-science: a real theory sticks its neck out. If nothing could ever count against it, it isn't telling you anything.
Where this lives →The capacity to have chosen otherwise. Whether it survives a physically determined universe is one of philosophy's longest unresolved fights.
Where this lives →Edmund Gettier's 1963 cases showing you can have a justified true belief that still isn't knowledge — you were right by accident. Three pages that broke a 2,000-year definition.
Where this lives →Aristotle's principle that each virtue sits between two vices — courage between cowardice and recklessness. Excellence is calibration, not extremity.
Where this lives →Chalmers' name for the real mystery: not what the brain does, but why any of it is accompanied by felt experience at all.
Where this lives →The claim that pleasure is the only intrinsic good. The Experience Machine is philosophy's most famous argument against it.
Where this lives →Anicca. The Buddhist observation that all conditioned things arise and pass — and that resisting this is a primary source of suffering.
Where this lives →In its philosophical sense: intentional action and its shaping consequences on the actor. A claim about how character forms, not a cosmic ledger of reward.
Where this lives →Kierkegaard's term for the commitment reason cannot underwrite — embracing what cannot be proved. Camus called it philosophical suicide; Kierkegaard called it the point.
Where this lives →For Heraclitus and the Stoics, the rational order running through the cosmos — the reason in things that our reason can align with.
Where this lives →Frankl's school of psychotherapy built on the premise that the primary human drive is not pleasure or power but meaning.
Where this lives →'Remember you will die.' Not morbidity but focus: the Stoic practice of letting mortality clarify what actually matters today.
Where this lives →The investigation of reality's most basic structure — being, time, cause, identity — beneath and behind what the sciences measure.
Where this lives →Explanation by purpose — accounting for something by what it is for rather than by what produced it.
Where this lives →The uncomfortable fact that praise and blame track outcomes we don't control. Two identical drivers; one child runs into the road. Same act, different guilt.
Where this lives →The view that moral truths hold only relative to cultures or individuals, not universally. Its rival, moral realism, says some things are wrong everywhere.
Where this lives →Premeditatio malorum: the Stoic practice of imagining loss in advance — not to darken life, but to blunt shocks and sharpen gratitude.
Where this lives →The view that life has no inherent meaning, value or purpose. Distinct from absurdism, which accepts that absence but refuses to stop living fully.
Where this lives →The extinguishing of craving and the suffering it produces. Not a place, and not annihilation — a release.
Where this lives →Do not multiply entities beyond necessity: prefer the explanation with the fewest assumptions that still accounts for everything.
Where this lives →The study of what exists and what it means for something to be. The oldest branch of metaphysics.
Where this lives →The modern reframe: if nothing matters cosmically, nothing is lost — and everything is permitted to matter personally. Freedom read out of the void.
Where this lives →The question of what makes you the same person over time, despite total physical and psychological change. The Ship of Theseus, applied to a life.
Where this lives →The disciplined study of experience as it is lived, from the first-person point of view. Husserl founded it; the existentialists ran with it.
Where this lives →Practical wisdom: the skill of judging what the situation actually calls for. For Aristotle, the master virtue that steers all the others.
Where this lives →The view that everything, including consciousness, is ultimately physical. Mary's Room is the classic thought experiment aimed at it.
Where this lives →Hume's puzzle: no number of past sunrises proves tomorrow's. All science leans on a pattern-holding assumption that can't itself be proved.
Where this lives →The felt quality of experience — what redness looks like from the inside, what pain feels like. The hardest thing for any theory of mind to explain.
Where this lives →The view that reason, not the senses, is the fundamental source of knowledge. Descartes' starting point.
Where this lives →Camus' answer to the absurd: a permanent confrontation, refusing both despair and false hope, and living with lucid defiance.
Where this lives →The cycle of birth, death and rebirth driven by craving — the wheel Buddhist practice aims to step off.
Where this lives →The systematic doubt that we can know what we claim to know. A method as much as a doctrine — Descartes used it to find bedrock.
Where this lives →Teaching by questioning: exposing contradictions in a belief until something sturdier is found. Socrates called himself a midwife of ideas.
Where this lives →The position that only your own mind is certain to exist. Nearly impossible to refute, and nearly impossible to believe.
Where this lives →The end, goal or purpose of a thing. For Aristotle, everything has a telos, and a good life consists in fulfilling ours.
Where this lives →The collision between our demand for meaning and a universe that gives none. Camus insisted it exists in neither the world nor us, but in the confrontation between them.
Where this lives →Hume's observation that no description of how the world IS can, by itself, tell you how it OUGHT to be. Facts don't generate values without a bridge.
Where this lives →An imagined scenario designed to isolate an intuition and test a theory against it. The trolley, the ship, and the experience machine are all thought experiments.
Where this lives →The view that the right action is the one producing the best overall outcome — usually the greatest wellbeing for the greatest number.
Where this lives →Rawls' device for fairness: design society without knowing who you'll be in it. Rules chosen blind are rules chosen just.
Where this lives →An approach that asks what kind of person to be rather than which rules to follow. The right act is what a person of good character would do.
Where this lives →Nietzsche's name for the fundamental drive he saw beneath life — not domination primarily, but growth, overcoming, self-expansion.
Where this lives →Effortless action: the Taoist art of acting with the grain of things rather than against it. Not passivity — timing.
Where this lives →Nietzsche's 'overhuman': one who creates values rather than inheriting them. Widely misread; for Nietzsche it was a task of self-overcoming, not superiority over others.
Where this lives →Emptiness. Nāgārjuna's claim that nothing possesses independent, intrinsic existence — everything arises in dependence on something else.
Where this lives →No term matches that. Try a broader word — or ask the question instead →
Philosophy invents vocabulary for the same reason medicine does: because the distinctions are real and ordinary language blurs them. "The absurd" is not a synonym for "pointless." Eudaimonia is not "happiness." Nihilism and absurdism are not the same doctrine, and mistaking one for the other is how most arguments about meaning go wrong in the first five minutes. Learn the words and the arguments get sharper immediately.
The collision between our demand for meaning and a universe that offers none. Camus stressed it lives in the confrontation, not in the world or in us alone.
Aristotle's word for the highest human good — flourishing. Not a feeling but an activity: exercising reason and virtue excellently across a whole life.
The view that life has no inherent meaning or value. Absurdism accepts the same absence but insists we live fully and defiantly anyway.
Definitions are written in plain language and follow the standard scholarly usage set out in the sources above. Where philosophers disagree about a term, the entry says so. Educational content.