Plato

Justice

Justice is harmony: each part of the soul and city doing its proper work.

Good and Evil

The Good is the highest Form: source of all being, beauty, and truth.

Virtue and Vice

Virtue is the harmony of the soul: wisdom, courage, temperance, and justice together.

Happiness

Happiness belongs to the just soul: the well-ordered life is the only life worth living.

Love

Eros is the soul's ascent from beautiful bodies to the Beautiful itself.

Courage

Courage is knowledge of what is truly worth fearing, not mere endurance in battle.

Desire

Desire is the soul's restless reaching toward what it lacks; eros is the force that drives the ascent from bodily appetite to the vision of the Good.

Punishment

Punishment is medicine for the soul: the wrongdoer who escapes it is sicker than the one who submits.

Duty

Justice as internal harmony creates duty; the just man acts rightly because justice is essential to the soul's health.

Emotion

The passions belong to the lower parts of the soul; reason must govern spirit and appetite for the soul to be harmonious.

Pleasure and Pain

Pure pleasures of the mind surpass mixed bodily pleasures; the good life blends pleasure with wisdom, but wisdom takes precedence.

Habit

The early shaping of the soul by repeated action lays the ground on which virtue or vice is later built.

Temperance

Temperance is the agreement of the whole soul and city that reason should rule — not the destruction of desire but its proper ordering.

Custom and Convention

Justice belongs to nature, not convention; the Sophists who reduce right to custom are wrong about the soul.

Law

Good law is reason free of passion: the rule of intelligence embodied in the polity.

War and Peace

War originates in greed, luxury, and appetite: a symptom of political and moral disorder.

Democracy

Democracy is liberty without restraint, and its natural end is tyranny.

State

The state is the soul writ large; a just polity mirrors the rational ordering of the just person.

Wealth

Wealth corrupts the soul and the city; the love of money is the root of oligarchic decay.

Revolution

Constitutions degenerate in a fixed cycle, and revolution follows the corruption of the ruling class.

Tyranny

The tyrant is the most wretched of men, enslaved to his own appetites, ruling by fear and making the city a mirror of his disordered soul.

Citizen

True citizenship is devotion to the city's good, shaped by education and soul-type, not by birth or occupation.

Slavery

Slavery belongs to the household of the just city; the question is treatment, not legitimacy.

Constitution

The best constitution mixes monarchy and democracy, binding even rulers to the authority of law.

Monarchy

The philosopher-king rules by wisdom, not by law; monarchy is the best regime when the ruler truly knows.

Aristocracy

The best city is ruled by those who know the Good; philosopher-kings are the aristocratic ideal fulfilled.

Oligarchy

Oligarchy is a city divided by wealth, where love of money replaces love of honor, and the poor are excluded from rule.

God

The divine is the Form of the Good: source of being and intelligibility, known by the mind.

Soul

The soul is immortal and rational. Philosophy is preparation for its liberation from the body.

Being

What truly is, is what is unchanging: the Forms, not the shifting world of sense.

Cause

The true cause of anything is not its matter but the Form and the Good for which it exists.

Time

Time is the moving image of eternity: the ordered succession that mirrors the unchanging Forms.

Immortality

The soul is immortal because it participates in the Form of Life and cannot admit its opposite.

Sin

Sin is the disorder of the soul: to act unjustly is not merely to wrong another but to corrupt oneself, and the tyrant who does what he wishes is the most wretched of men.

Theology

Theology is the highest part of philosophy: knowledge of divine things reached through dialectic.

Prophecy

Prophetic madness is a divine gift, higher than human calculation; the gods speak through those whose reason is suspended.

Metaphysics

Dialectic is the supreme science, grasping the Forms and ascending to the Good, the ground of all being and knowing.

Chance

What the many call chance is really the work of mind, necessity, and divine art cooperating.

Change

What is always becoming and never is cannot be truly known; only the unchanging Forms can.

Form

Forms are the eternal, separate archetypes in which sensible things participate and by which they are what they are.

Matter

Beneath the visible world lies a formless receptacle: that which receives all things yet is never any of them.

Necessity and Contingency

Reason persuades necessity; the cosmos is built where intelligible order meets the wandering cause.

One and Many

If the One simply is, it cannot be many; yet whatever is at all is already both one and many.

Space

Space is the receptacle, the formless nurse of all becoming, apprehended only by a kind of spurious reason.

World

The world is a living creature fashioned by a divine craftsman who looked to the eternal Forms as his model.

Opposition

Non-being is not the negation of being but the mark of difference, and opposition among the great kinds is what makes discourse possible.

Relation

The forms themselves are relational: each great kind communes with others, and none can be grasped in isolation.

Same and Other

Every Form is the same as itself and other than every other Form; sameness and otherness are woven into the structure of reality.

Quality

Sensible qualities belong to the world of becoming; the Forms, which truly are, stand beyond hot and cold, sweet and bitter.

Quantity

Number belongs to the intelligible realm, and the study of arithmetic trains the soul to ascend from becoming to being.

Angel

Between gods and men stands a whole order of intermediate spirits, daemons who ferry prayers upward and answers down.

Eternity

Eternity is the unchanging being of the Forms; time is its moving image.

Truth

Truth is eternal and unchanging: a property of what is, not of what seems.

Knowledge

True knowledge is of the Forms: eternal, unchanging realities grasped by reason, not sense.

Mind

Mind (nous) grasps the Forms: its proper objects are eternal, and it knows by recollection.

Experience

Sense-experience does not supply knowledge but awakens the soul's recollection of the forms it once beheld.

Language

Names either attach to things by nature, reflecting their essence, or by convention; Plato leaves the question open.

Memory and Imagination

All learning is recollection; the soul's prior knowledge of the Forms is recovered through questioning.

Rhetoric

Rhetoric is flattery unless joined to knowledge of truth; the orator who persuades without knowing what is just does harm.

Opinion

Opinion concerns the changing world of becoming; knowledge concerns the eternal world of being; only philosophy can bridge the gap between them.

Idea

Ideas are the eternal Forms: the unchanging realities that particular things imitate and the mind ascends to know.

Judgment

Judgment is the soul's silent dialogue with itself, reaching a conclusion about what is or is not the case.

Sense

The senses show us shadows on a cave wall; true knowledge requires the mind to ascend beyond what can be seen or touched.

Sign and Symbol

Names are neither arbitrary nor perfectly natural: the question is whether language can reach the nature of things.

Hypothesis

A hypothesis is a provisional resting place for thought, a rung on the ladder that reason must eventually kick away.

Mathematics

Mathematical objects are intelligible Forms grasped by reason alone, not abstracted from sense experience.

Dialectic

Dialectic is the highest science, ascending from hypothesis to the unhypothetical first principle through pure thought.

Principle

The first principle is the Form of the Good, unhypothetical and self-grounding, from which all intelligibility flows.

Reasoning

Reasoning is the soul's movement from hypothesis to first principle, ascending through dialectic to the Good.

Logic

Dialectic is the highest intellectual method, ascending from hypotheses to unconditioned first principles — logic is not a set of rules but a path to the Forms.

Definition

The demand for definition is the demand for the universal: Socrates' search for what virtue or beauty 'really is' sets the agenda for all subsequent philosophy.

Universal and Particular

Universals are Forms: separately existing, eternal objects that give particular things their nature and make definition and science possible.

Education

Education is the turning of the soul toward the Good, a conversion of the whole person.

Wisdom

Wisdom belongs to the philosopher who grasps the Good and orders soul and city by its light.

Prudence

Only genuine knowledge of the Good enables right action — the statesman who governs by opinion rather than knowledge cannot explain or replicate success.

Philosophy

The philosopher ascends from shadows to the light of the Good, then returns to the cave to govern.

Man

Man is a composite soul: reason, spirit, and appetite in uneasy alliance, with reason's rule defining the good human life.

Beauty

Beautiful things participate in Beauty itself: eternal, unchanging, the object of eros's ascent.

Art

Art is imitation of imitation, thrice removed from truth, and dangerous when it substitutes for philosophy.

Poetry

Poetry is imitation at two removes from reality; the poet competes with the philosopher and must be banished from the just city.

Life and Death

The soul is immortal; death is the separation of soul from body, and philosophy is preparation for that release.

Animal

Animals are ensouled creatures ranked by the grade of soul they possess; the brute is the form toward which degraded human souls descend.

Element

The four elements are regular polyhedra built from triangles, making matter itself a species of geometry.

Medicine

Medicine is to the body what justice is to the soul, and a city that needs too many doctors is already sick.

Astronomy

The study of the heavens orders the soul: astronomical contemplation is training in reason itself.

Physics

The physical world is a moving image of eternity, fashioned by a divine craftsman according to eternal mathematical forms; physics can offer a likely story, not certain knowledge.