Concepts

theodicy

The branch of philosophical theology that attempts to justify belief in a good and powerful God in the face of suffering and evil.

The constructive theistic response to the problem of evil — coined by Leibniz in 1710 and the central engine of philosophical theology since.

natural-theology

The discipline that seeks to establish or defend claims about God's existence, nature, and providence using reason alone, without appeal to revelation or sacred text.

The project of arguing from publicly available premises — reason, the cosmos, conscience — to substantive conclusions about God.

cosmological-argument

The family of a posteriori arguments for God's existence that proceed from observed features of the world (motion, causation, contingency) to a first cause or necessary being, developed across Aristotelian, Islamic, Thomist, and Leibnizian versions.

The cosmological argument is the family of a posteriori arguments for God's existence that proceed from observed features of the world — motion, causation, contingency — to a first cause or necessary being.

trinity

The central Christian doctrine that the one God exists as three coequal, coeternal persons (Father, Son, and Holy Spirit), articulated at the Councils of Nicaea (325) and Constantinople (381) and continuously contested across the patristic, medieval, and modern theological traditions.

The Trinity is the central Christian doctrine that the one God exists as three coequal, coeternal persons — Father, Son, and Holy Spirit — a doctrine that has organized Christian theology and shaped Western philosophy of personhood for seventeen centuries.

tabula-rasa

The empiricist doctrine that the human mind at birth contains no innate ideas or principles, originating with Aristotle and given its canonical modern statement by Locke in 1689.

Tabula rasa is the doctrine that the human mind at birth contains no innate ideas or principles — a blank slate that experience writes on — most associated with John Locke's 1689 Essay Concerning Human Understanding.

ontological-argument

The family of a priori arguments for God's existence that proceed from the concept of God alone, originating with Anselm's 1078 Proslogion and continuously contested across the rationalist, Kantian, and contemporary analytic traditions.

The ontological argument is the family of a priori arguments for God's existence that proceed from the concept of God alone — the only major arguments for God in the Western tradition that claim demonstration without empirical premises.

problem-of-evil

The apparent inconsistency between the existence of suffering in the world and the existence of an omnipotent, omniscient, perfectly good God — the most-discussed single argument against theism, with major formulations from Epicurus through Hume and the contemporary analytic literature.

The problem of evil is the apparent inconsistency between the existence of suffering in the world and the existence of a God who is omnipotent, omniscient, and perfectly good — the most-discussed single argument against theism in the Western philosophical tradition.

identity-reconstruction

The structural process of rebuilding the self after a load-bearing belief system has collapsed, treated not as a cognitive update but as a re-architecting of the framework through which selfhood and meaning are organized.

Identity reconstruction is the structural process of rebuilding the self after a load-bearing belief system has collapsed — not a cognitive operation of updating propositions but a difficult, time-extended re-architecting of the framework through which selfhood and meaning are housed.

values-construction

The deliberate building of a personal value system after the inherited framework has ceased to be load-bearing, treated as an intentional act of construction rather than discovery or inheritance.

Values construction is the intentional building of a personal value system after the inherited one has ceased to be load-bearing — a deliberate act of construction in conditions where the older mode of inheriting values is no longer fully available.

coherence-without-certainty

The epistemic posture of holding beliefs as functionally coherent and provisionally adequate without claiming demonstrative certainty — the alternative to both dogmatic conviction and skeptical paralysis.

Coherence without certainty is the epistemic posture of holding beliefs as functionally coherent and provisionally adequate without claiming demonstrative certainty for them — the mature alternative to both dogmatic conviction and skeptical paralysis.

inherited-vs-chosen-belief

The applied-epistemology distinction between beliefs absorbed pre-reflectively from one's culture and beliefs deliberately taken up after examination, with consequences for how each kind is held, defended, and revised.

Inherited vs. chosen belief is the diagnostic distinction between beliefs absorbed pre-reflectively from one's family, culture, and tradition, and beliefs deliberately taken up after examination — a distinction that matters because the two have different stability, different defensibility, and different relations to the self that holds them.

is-ought-gap

Hume's observation that moral writers regularly slide from descriptive (is) claims to normative (ought) claims without justifying the inference — sometimes called Hume's Law or the naturalistic fallacy.

The Is-Ought Gap is Hume's observation that moral writers regularly slide from descriptive (is) claims to normative (ought) claims without justifying the inference — a foundational problem in metaethics ever since.

bundle-theory

Hume's account of the self (and, by extension, of objects) as a bundle of perceptions held together by relations of resemblance and causation rather than by an underlying substance.

Bundle Theory is Hume's account of the self as a bundle of perceptions held together by relations of resemblance and causation — with no underlying substantial self detectable in introspection.

the-absurd

The existentialist (especially Camusian) concept naming the gap between the human desire for meaning and the universe's silence on the question — the fundamental human condition once consolatory frameworks have collapsed.

The Absurd is the existentialist concept naming the gap between the human desire for meaning and the universe's silence on the question — the fundamental human condition once consolatory frameworks have collapsed.

principle-of-sufficient-reason

Leibniz's principle that nothing happens without a sufficient reason why it should be so rather than otherwise — the central methodological commitment of his rationalism and one of the most contested principles in modern metaphysics.

The Principle of Sufficient Reason is Leibniz's principle that nothing happens without a sufficient reason why it should be so rather than otherwise — the central methodological commitment of his rationalism and one of the most contested principles in modern metaphysics.

substance-monism

Spinoza's metaphysical doctrine that there is one and only one substance — infinite, self-caused, identical with God or Nature — of which everything else is a mode.

Substance Monism is Spinoza's doctrine that there is one and only one substance — infinite, self-caused, identical with God or Nature — of which everything else (minds, bodies, individual things) is a mode rather than a separate substance.

master-slave-dialectic

Hegel's analysis in Phenomenology of Spirit IV of the struggle between two self-consciousnesses for recognition — a foundational text for subsequent philosophy of recognition, Marxist analysis, and post-colonial thought.

The Master-Slave Dialectic is Hegel's analysis of the struggle between two self-consciousnesses for recognition — the most influential single passage of Phenomenology of Spirit and a foundational text for subsequent philosophy of recognition, Marxist analysis, and post-colonial thought.

bad-faith

Sartre's name for the mode of consciousness that flees its own freedom by treating itself as a fixed thing rather than the open activity it actually is — self-deception that requires simultaneously knowing and not knowing the same thing.

Bad Faith is Sartre's name for the mode of consciousness that flees its own freedom by treating itself as a fixed thing — self-deception that requires simultaneously knowing and not knowing the same thing.

alienation

Marx's concept naming the structural condition under capitalism in which workers are estranged from the product of their labor, from the activity of labor, from their species-being, and from other workers.

Alienation is Marx's concept naming the structural condition under capitalism in which workers are estranged from the product of their labor, from the activity of labor, from their species-being, and from other workers.

being-toward-death

Heidegger's analysis of human existence as essentially structured by its relation to its own coming death — the recognition of which is what makes authentic existence possible.

Being-toward-Death is Heidegger's analysis of human existence as essentially structured by its relation to its own coming death — the recognition that makes authentic existence possible.

synthetic-a-priori

Kant's central epistemological category: knowledge that is both synthetic (extending what is known beyond the analysis of concepts) and a priori (independent of experience for its justification).

Synthetic A Priori is Kant's central epistemological category: knowledge that extends our understanding beyond the analysis of concepts but is independent of experience for its justification — the kind of knowledge whose possibility is the central question of the Critique of Pure Reason.

eternal-recurrence

Nietzsche's doctrine that every moment of existence will recur infinitely many times, identically — functioning both as a thought experiment testing one's relation to life and (on the strongest reading) as a cosmological claim about the structure of time.

Eternal Recurrence is Nietzsche's doctrine that every moment of existence will recur infinitely many times, identically — a thought experiment testing one's relation to life and (on the strongest reading) a cosmological claim about the structure of time.

aufhebung

Hegel's technical term for the dialectical movement that simultaneously negates, preserves, and elevates a position into a higher synthesis — the central operation of dialectical thinking.

Aufhebung is Hegel's name for the dialectical movement that simultaneously negates, preserves, and elevates a position into a higher synthesis — the central operation of dialectical thinking, often translated as 'sublation'.

will-to-power

Nietzsche's contested doctrine that the fundamental drive of all living things — and on the most ambitious reading of all reality — is the will to expand, intensify, and overcome itself.

The Will to Power is Nietzsche's contested doctrine that the fundamental drive of all living things — and on the most ambitious reading of all reality — is the drive to expand, intensify, and overcome itself.

authenticity

The existentialist value of being what one is in the deepest sense — living from one's own freedom and recognition of finitude rather than from inherited roles, social conformity, or self-deception.

Authenticity is the existentialist value of being what one is in the deepest sense — living from one's own freedom and recognition of finitude rather than from inherited roles, social conformity, or self-deception.

transcendental-idealism

Kant's metaphysical position: appearances are transcendentally ideal (depending on the structures of cognition) but empirically real; things in themselves, independent of cognition, are not knowable.

Transcendental Idealism is Kant's metaphysical position: what we know is appearances (structured by the mind's forms of intuition and categories), not things as they are in themselves — which remain in principle unknowable.

cogito

Descartes's foundational principle — cogito ergo sum, 'I think, therefore I am' — the indubitable certainty of the thinking subject's existence, recovered through systematic doubt as the foundation of modern philosophy.

The Cogito is Descartes's foundational principle — 'I think, therefore I am' — the indubitable certainty of the thinking subject's existence from which modern philosophy attempts to rebuild knowledge.

problem-of-induction

Hume's argument that inductive inference — from observed cases to unobserved ones — cannot be rationally justified without circularity, and yet underlies most of what counts as empirical knowledge.

The Problem of Induction is Hume's argument that inductive inference — the move from past regularities to future predictions — cannot itself be rationally justified, even though it underlies most of what we count as empirical knowledge.

categorical-imperative

Kant's formulation of the moral law as an unconditional principle of action — act only on that maxim which you can will to be a universal law — the foundational doctrine of deontological ethics.

The Categorical Imperative is Kant's formulation of the moral law as an unconditional principle of action — the foundational doctrine of deontological ethics and the central alternative to virtue and utilitarian frameworks.

natural-law

The doctrine that there is a moral law accessible to human reason, grounded in human nature and the rational structure of reality, distinct from but related to divine command and positive law.

Natural Law is the doctrine that moral truths are accessible to reason — grounded in human nature itself — distinct from divine command, distinct from positive law, but ultimately consistent with both.

essence-and-existence

The metaphysical distinction, developed by Avicenna and Aquinas, between what a thing is (essence) and the fact that it is (existence) — with the corollary that only in God are essence and existence identical.

Essence and Existence is the metaphysical distinction between what a thing is and the fact that it is — with the doctrine, developed by Avicenna and Aquinas, that only in God are essence and existence identical.

five-ways

Aquinas's five arguments for the existence of God in Summa Theologiae Ia q.2 a.3, proceeding from observed features of the world (motion, causation, contingency, gradation, order) to a first principle that everyone calls God.

The Five Ways are Aquinas's five proofs for the existence of God — each proceeding from an observed feature of the world (motion, causation, contingency, gradation, order) to a first principle.

original-sin

The Christian doctrine that human nature is wounded by inherited disorder transmitted from the fall of Adam, leaving the will divided against itself and unable consistently to will the good without grace.

Original Sin is the Christian doctrine that human nature is wounded by inherited disorder — the will is divided against itself, unable to consistently will the good without divine grace.

four-causes

Aristotle's doctrine that every thing or event has four kinds of explanation — material, formal, efficient, and final — and that complete understanding requires grasping all four.

The Four Causes are Aristotle's doctrine that every thing has four kinds of explanation — what it is made of, what it is, what brought it about, and what it is for — each of which contributes to understanding it.

substance

The Aristotelian metaphysical category naming what fundamentally exists — the bearer of properties and the primary subject of predication, contrasted with accidents that depend on it.

Substance is the Aristotelian answer to the question 'what fundamentally exists' — the bearer of properties, the primary subject of predication, the thing that exists in its own right rather than as a feature of something else.

telos

The Greek term for end, purpose, or completion — the goal toward which a thing naturally tends, foundational to Aristotelian metaphysics and ethics.

Telos is the Greek term for end or purpose — the goal toward which a thing naturally tends and the structural principle of Aristotelian metaphysics and ethics.

doctrine-of-the-mean

Aristotle's doctrine that each moral virtue lies as a mean between two vices — one of excess and one of deficiency — found by practical wisdom in the particular situation.

The Doctrine of the Mean is Aristotle's account of how moral virtues are structured: each virtue is a mean between two vices, one of excess and one of deficiency, with the right amount found by practical wisdom in the particular situation.

episteme

The Greek term for knowledge in the strongest sense — systematic, grounded, demonstrable understanding, contrasted with opinion (doxa) as the lower epistemic state.

Episteme is the Greek name for knowledge in the strict sense — systematic, demonstrable understanding, contrasted across the tradition with opinion as the lower epistemic state.

form

The Platonic doctrine that what is fundamentally real is a set of eternal, unchanging, abstract patterns — the Forms — in which the changing things we perceive merely participate.

The Form is the Platonic answer to the question of what is fundamentally real: not the changing things we see, but eternal, abstract patterns that the visible world only imperfectly imitates.

allegory-of-the-cave

Plato's famous image in Republic VII of prisoners chained in an underground cave, mistaking shadows for reality — the canonical illustration of the soul's ascent from ignorance to knowledge.

The Allegory of the Cave is Plato's image of prisoners chained underground watching shadows they take for reality — the most famous illustration in Western philosophy of the soul's ascent from ignorance to knowledge.

justice

The classical Western concept naming what is rightly due — to persons, to claims, to the parts of a soul or a city — and the central organizing concept of political philosophy since Plato.

Justice is the central concept of Western political and ethical philosophy: what is rightly due, and how it should be distributed, ordered, or restored.

apatheia

The Stoic doctrine of freedom from passion — not the absence of feeling, but the absence of the disturbing emotions that arise from mistaken judgments about what is good and bad.

Apatheia is the Stoic name for freedom from passion — not numbness, but the absence of the disturbing emotions that arise when one judges falsely about what matters.

amor-fati

The Stoic doctrine of loving fate — actively accepting whatever happens as the working of cosmic logos, rather than merely tolerating it.

Amor fati is the doctrine of loving fate — not the resigned acceptance of what cannot be changed, but the active affirmation of what is as the working of cosmic order.

mythos

The Greek term for story, myth, or narrative — contrasted across the philosophical tradition with logos as a distinct mode of conveying truth.

Mythos is the Greek term for narrative truth — the mode of conveying meaning through story and image, set against logos throughout the philosophical tradition as a serious alternative rather than mere fiction.

ataraxia

The Hellenistic ideal of mental tranquility — the settled, undisturbed state of soul that Epicureans and Skeptics took to be the goal of philosophy.

Ataraxia is the ancient Greek name for the settled, undisturbed state of soul that Epicureans and Skeptics, in different ways, took to be the highest human achievement.

aporia

The Greek term for productive perplexity — the recognition, often arrived at through dialectical questioning, that one does not in fact know what one thought one knew.

Aporia is the productive perplexity at the heart of Socratic philosophy — the state of recognized not-knowing that, far from being a failure of inquiry, is its actual beginning.

phronesis

Aristotle's name for practical wisdom — the trained capacity to perceive what a particular situation calls for and to act on it well.

Phronesis is the master virtue in Aristotelian ethics: the trained perception that recognizes what a particular situation requires, where no rule could specify the answer in advance.

dialectic

The method of arriving at truth through structured opposition — question and answer, thesis and counter-thesis, contradiction and resolution.

Dialectic is the philosophical method that treats disagreement not as failure but as the engine of getting to the truth.

belief-systems

The structured set of beliefs, values, and assumptions through which a person makes sense of the world — considered as architecture, not content.

A belief system is not what you believe — it is the structure that holds your beliefs in place, decides what you can question, and silently runs you when you're not looking.

free-will

The capacity — if it exists — of an agent to genuinely choose between alternatives in a way that is not wholly determined by prior causes.

Free will is the longest-running unresolved problem in Western thought: whether what you just did was up to you, or whether it merely felt like it was.

logos

The Greek term meaning word, reason, account, ratio — and behind all of these, the rational structure that makes reality intelligible.

Logos is the single most-migrated word in Western thought: it begins as 'reckoning' in Greek commerce, ends as 'the Word' in the Gospel of John, and is reborn in the 20th century as 'logic' itself.

virtue

The Greek concept of human excellence — the disposition that makes a thing or person good at being what it is.

Virtue, in the Greek sense, is not moral restraint; it is excellence — the disposition that makes a thing succeed at being the kind of thing it is.

eudaimonia

The Greek term for human flourishing — the life that goes well as a whole, not the life that feels good moment to moment.

Eudaimonia is the ancient Greek answer to 'what makes a human life good?' — and it doesn't mean what 'happiness' means today.

god

The classical concept: a maximally great being. Arguments for and against constitute much of philosophy of religion.

theodicy

The attempt to reconcile the existence of an all-good, all-powerful God with the existence of evil and suffering.

theory-of-forms

Plato's claim that abstract, perfect Forms are more real than the changing particulars that participate in them.

aesthetics

The philosophical study of beauty, art, and taste.

empiricism

The thesis that knowledge derives primarily from sensory experience.

truth

What it is for a claim to correspond to, cohere with, or work in reality.

utilitarianism

The view that the right action maximizes overall well-being or pleasure — Bentham and Mill's signature contribution.

deontology

Duty-based ethics: actions are right or wrong in themselves, regardless of consequences. Most associated with Kant.

justice

The proper distribution of benefits, burdens, rights, and punishments — from Plato's Republic to Rawls' fairness.

substance

That which exists independently and bears properties; the bedrock of classical metaphysics.

syllogism

Aristotle's three-line deductive argument form (e.g., All M are P; All S are M; therefore All S are P).

nihilism

The denial of objective meaning, value, or moral truth; Nietzsche framed it as the crisis modernity must overcome.

causation

The relation by which one event or state brings about another — contested from Aristotle's four causes to Hume's skepticism.

ontology

The study of being qua being — what it means for anything to exist.

social-contract

The idea that political authority is grounded in (hypothetical) agreement among the governed — Hobbes, Locke, Rousseau, Rawls.

rationalism

The thesis that reason, not experience, is the primary source of substantive knowledge.

liberty

Freedom from interference (negative) or capacity to act (positive); the axis of modern political debate.

metaphysics

The branch of philosophy that asks what fundamentally exists and what its nature is.

universals

Properties shared by many particulars; the central problem dividing realists, nominalists, and conceptualists.

virtue-ethics

An approach centered on character traits (virtues) rather than rules or outcomes — rooted in Aristotle, revived by Anscombe and MacIntyre.

consciousness

Subjective experience itself; the 'hard problem' is explaining why physical processes give rise to it.

epistemology

The study of knowledge — what it is, how we get it, and the limits of what can be known.

determinism

The thesis that every event is the necessary outcome of prior causes.

stoicism

The Hellenistic philosophy that virtue is the only true good and that flourishing comes from aligning with nature and accepting what's outside our control.

knowledge

Traditionally defined as justified true belief; problematized by Gettier and beyond.

ethics

The systematic study of right action, good character, and the structure of moral claims.

free-will

The capacity to act otherwise; the central battleground between libertarians, compatibilists, and hard determinists.

logic

The study of valid inference — the rules by which conclusions follow from premises.

skepticism

The position that knowledge is unattainable or radically uncertain — from Pyrrho to Descartes' demon.

existentialism

Existence precedes essence: humans must create meaning in a universe that doesn't supply it.

mind-body-problem

The question of how mental states relate to physical states — Descartes' dualism inaugurated the modern version.

faith-and-reason

The relationship between religious belief and rational justification — fideism, evidentialism, and everything between.