Philosophy Glossary

Daimon (δαίμων) — An intermediary entity between gods and humans in Greek cosmology. Socrates described his daimonion as an “inner voice” that prevented him from committing moral errors — never telling him what to do, but forbidding certain actions. Plato situates daimones as messengers between the divine and human worlds. The concept influenced Christian angelology and, via Goethe, German Romanticism. ...

Deduction / Induction — Two fundamental methods of reasoning. Deduction is reasoning in which the conclusion follows necessarily from the premises — if the premises are true, the conclusion cannot be false (Aristotelian syllogism, geometry). Induction moves from particular cases to probable generalizations — the basis of the modern scientific method (Bacon, Hume). The “problem of induction” (Hume): no number of past observations logically guarantees a universal future conclusion. ...

Dialectic (Dialektikê) — Originally, the art of dialogue and argumentation (Socrates: dialectic as a method of investigating truth through questions and answers). Plato makes it the philosopher’s supreme method, ascending from opinions to Ideas. Hegel radicalizes: dialectic is the movement of reality itself — through determinate negation and Aufhebung (sublation) — through which contradiction drives historical and logical development. (The formula “thesis, antithesis, synthesis” was popularized by Chalybäus, not by Hegel.) Marx “inverts” Hegel: dialectic operates in historical materiality, not in Spirit. ...

Doxa (δόξα) — “Opinion” or “belief,” opposed to genuine knowledge (episteme). For Parmenides, doxa is the illusory path of the senses, opposed to reason which reveals Being. For Plato, doxa occupies an intermediate level on the divided line: it is knowledge of images and sensible objects, not of the Ideas. Husserl uses Urdoxa to designate the fundamental, pre-reflective belief in the existence of the world. ...

Dualism — A metaphysical position that posits two irreducible principles or substances. The most influential is Cartesian dualism: mind (res cogitans) and body (res extensa) are radically different substances. The classic problem: how do two such distinct substances interact? Other forms: good/evil dualism (Manichaeism), phenomenon/thing-in-itself (Kant), sacred/profane. ...

Dynamis / Energeia (δύναμις / ἐνέργεια) — A fundamental Aristotelian conceptual pair: dynamis is potency, capacity, or possibility; energeia is act, fulfillment, or actual exercise. A seed has the tree in dynamis (potency); the mature tree is that potency realized in energeia (act). Movement is the passage from potency to act. The Unmoved Mover moves everything by being pure act — without residual potency — meaning it cannot fail to be what it is. ...

Eidos (εἶδος) — “Form,” “visible aspect,” or “idea.” In Plato, the eidos are the Ideas or Forms — eternal, immutable, universal realities that sensible objects merely imitate (mimesis). A particular horse participates (methexis) in the Idea of Horse. In Aristotle, the eidos is each thing’s inner form — what makes it what it is — inseparable from matter (hyle). Husserl revives the term to designate the eidetic essence grasped by phenomenological intuition. ...

Empiricism — An epistemological tradition holding that sensory experience is the source and limit of knowledge. Locke: the mind is a “blank slate” filled by experience. Berkeley: to be is to be perceived (esse est percipi). Hume: ideas are copies of sensory impressions; reason alone knows nothing of the world. Logical empiricism of the Vienna Circle (20th century) demands that meaningful propositions be empirically verifiable. ...

Episteme (ἐπιστήμη) — “Scientific knowledge” or “true knowing,” as opposed to doxa (opinion) and techne (practical skill). For Plato, it is knowledge of the Ideas — eternal, immutable, accessible only to reason. Aristotle systematizes: episteme is demonstrative, deductively derived from first principles, and concerns the necessary. Foucault reappropriates: episteme is the implicit epistemic soil that defines, in each historical era, what can be thought and said. ...

Epoché (ἐποχή) — “Suspension of judgment.” In Pyrrhonian skepticism, it is the abstention from affirming or denying any proposition about reality, leading to ataraxia. Husserl redeployes the term in phenomenology: the phenomenological reduction (“bracketing the world”) suspends the natural thesis of the world’s existence to investigate the pure structure of consciousness and its intentional acts. ...

Essence / Existence — A fundamental metaphysical pair. Essence is what a thing is (its definition, form, nature). Existence is the fact that it is (that there is something). In scholasticism, essence precedes and delimits existence: God exists necessarily because his essence includes existence. Sartre inverts this: “existence precedes essence” — the human being first exists, then defines what it is through its choices. This founds atheist existentialism. ...

Eudaimonia (εὐδαιμονία) — “Flourishing,” “happiness,” or “well-being” — an imprecise translation, since it designates a state of lived excellence, not merely pleasure. For Aristotle, eudaimonia is the supreme human good (telos of life), achieved through the exercise of virtues according to reason over a complete lifetime. It is not a passing feeling, but an activity. The Stoics identify it with pure virtue; the Epicureans, with freedom from disturbance (ataraxia). ...

Freedom — A central concept in ethics, politics, and metaphysics. For the Stoics, freedom is internal: free is the one who governs their passions through reason. For Kant, transcendental freedom is the capacity to act according to moral law, independent of natural determinism. For Sartre, the human being is “condemned to be free”: one cannot escape choice, since even not choosing is a choice. In political philosophy: negative liberty (absence of coercion, Berlin) vs. positive liberty (capacity for self-realization). ...

Geist — German for “spirit” or “mind,” it becomes a central technical concept in Hegel’s philosophy. The Geist is not the individual mind but the universal Spirit that develops dialectically through nature, history, and human institutions until reaching complete self-knowledge in absolute knowing. Marx inherits the term but materializes it: the “spirit” of an era is determined by material conditions of production, not by itself. ...

Gnosis (γνῶσις) — Greek for “knowledge,” specifically the spiritual or revealed knowledge that liberates the soul. In Gnostic currents of the first centuries CE (Valentinians, Basilideans), gnosis is salvific knowledge of the soul’s divine origin, imprisoned in the material world created by an inferior demiurge. It differs from faith (pistis) as direct, experiential knowledge of the divine. Jung revived the concept for his psychology of archetypes and the collective unconscious. ...

Hedonism — An ethical doctrine holding that pleasure (hedone) is the highest good and the only genuine motive for action. The hedonism of Aristippus of Cyrene identified the good with immediate, bodily pleasure. Epicurus distinguished pleasures: kinetic (active, intense, potentially disturbing) from katastematic (stable, absence of pain — aponia — and disturbance — ataraxia). Bentham’s utilitarianism makes pleasure and pain the foundation of moral calculation. ...

Hylomorphism — The Aristotelian theory that every sensible substance is composed of hyle (matter) and morphé (form). Matter is the indeterminate substrate; form is the principle of determination and organization. The soul is the form of the body. Hylomorphism was adopted and adapted by medieval Scholasticism (Thomas Aquinas) and continues to be debated in contemporary philosophy of mind regarding the relationship between mind and brain. ...

Idealism — A metaphysical position holding that reality is fundamentally mental or ideal in nature. Subjective idealism (Berkeley): only minds and their ideas exist. Transcendental idealism (Kant): we cannot know things in themselves, only the world as structured by the mind. Absolute idealism (Hegel): the real is the rational; reality is the development of Spirit (Geist) coming to know itself. Opposes realism and materialism. ...

Immanence / Transcendence — Immanence designates what is internal to a system, process, or being. Transcendence designates what lies beyond, outside, or above. Is God transcendent to the world (theism) or immanent to it (Spinoza’s pantheism)? For Kant, the Ideas of reason (soul, world, God) are transcendent — they exceed possible experience. For Sartre, consciousness is pure transcendence — always “beyond” itself, directed toward the world and the future. ...

Intentionality — The fundamental property of consciousness of being directed toward objects. Coined by Brentano and developed by Husserl: every mental act (perception, desire, imagination, memory) is always an act of or about something. There is no contentless consciousness. Intentionality is the mark of the mental and the starting point of phenomenological analysis. Heidegger transforms it: human Dasein is always already “in the world,” not enclosed in a subjective sphere needing a “bridge” to objects. ...