🤔 Philosophy Complete 25,000+ Word Guide to Western & Eastern Thought

H3: The Milesians

Thales (c. 624-546 BCE) considered the first Western philosopher. He proposed that water is the arche (first principle) of all things. While his specific claim seems naive, his approach was revolutionary—seeking natural explanations rather than mythological ones. He also predicted a solar eclipse and was considered one of the Seven Sages of Greece.

Anaximander (c. 610-546 BCE), Thales' student, proposed the apeiron (the boundless, indefinite) as the arche. He argued that the ultimate reality must be something without specific qualities, from which all determinate things emerge. He also developed an early theory of evolution—humans must have evolved from other animals because human infants need prolonged care to survive.

Anaximenes (c. 585-528 BCE) proposed air as the arche. He explained how different substances arise through rarefaction and condensation—air becomes fire when rarefied, wind, cloud, water, earth, and stone when increasingly condensed.

H3: Heraclitus and Parmenides

Heraclitus (c. 535-475 BCE) emphasized change and flux. "You cannot step into the same river twice" because both the river and the person have changed. He saw fire as the fundamental element, symbolizing constant change. Yet he also believed in a underlying order—the logos—that governs all change. "All things come to be in accordance with this logos."

Parmenides (c. 515-450 BCE) took the opposite view. Using logic, he argued that change is impossible. Being is, non-being is not. If something comes into being, it would have to come from non-being, which is impossible. Therefore, what-is must be eternal, unchanging, indivisible, and one. The world of change we experience is illusion. His student Zeno created famous paradoxes (Achilles and the tortoise) to defend Parmenides.

H3: Pythagoras and Others

Pythagoras (c. 570-495 BCE) saw mathematical relationships as fundamental—"all is number." He discovered mathematical ratios in musical harmony and applied mathematical thinking to cosmology. His religious community believed in transmigration of souls and pursued purification through intellectual and ascetic practices.

Empedocles (c. 494-434 BCE) proposed four elements (earth, air, fire, water) combined by Love and separated by Strife. Anaxagoras (c. 500-428 BCE) introduced nous (mind) as cosmic principle. Democritus (c. 460-370 BCE) developed atomism—all reality consists of atoms and void, a remarkably prescient theory.

H3: The Socratic Method

Socrates wrote nothing, known through Plato's dialogues. His method (elenchus) involved questioning people about their beliefs, exposing contradictions, and leading them to recognize their ignorance. This dialectical process aimed not to win arguments but to achieve genuine understanding.

The typical pattern: Socrates asks for a definition (e.g., "What is justice?"). The interlocutor offers a definition. Socrates tests it with counterexamples, showing it's inadequate. The interlocutor revises. The process continues until either a satisfactory definition emerges or the interlocutor admits confusion (aporia).

Socratic irony: Socrates claimed ignorance ("I know that I know nothing") yet showed others that their supposed knowledge was hollow. This humility opened the way to genuine inquiry. His method remains fundamental to education, law, and philosophy.

H3: Socratic Teachings

"The unexamined life is not worth living." For Socrates, philosophical examination is essential to human flourishing. Without questioning our beliefs and values, we live at the level of animals—driven by convention and impulse rather than genuine understanding.

"Know thyself." Self-knowledge is the foundation of wisdom. Understanding our own ignorance is the beginning of genuine learning.

Virtue is knowledge. Socrates believed that no one does wrong willingly. If people truly understood what was good, they would do it. Wrongdoing results from ignorance, not evil intention. This intellectualist ethics influenced later philosophers but raises questions about weakness of will (akrasia).

H3: Theory of Forms

Plato's most famous doctrine: the physical world is not the true reality. Beyond it exists a realm of Forms (or Ideas)—perfect, eternal, unchanging archetypes of everything we experience. Particular beautiful things participate in the Form of Beauty; just actions participate in the Form of Justice.

Characteristics of Forms: They are non-physical, eternal, unchanging, perfect, and known through reason rather than senses. They provide the standards by which we judge particulars. The Form of the Good is the highest Form, illuminating all others.

Arguments for Forms: We can recognize that many things share a property (e.g., many beautiful things). This requires a single Form of Beauty. We can make judgments about perfection (a circle is imperfectly drawn) implying knowledge of perfect Form.

H3: Allegory of the Cave

In Book VII of The Republic, Plato presents his most famous image. Prisoners are chained in a cave, seeing only shadows on the wall. They believe these shadows are reality. One prisoner is freed, turns around, sees the puppets casting shadows, and eventually ascends to the outside world, seeing real objects and ultimately the sun.

Interpretation: The cave is the physical world of appearances. The shadows are ordinary experience. The journey out is philosophical education, turning the soul toward truth. The sun represents the Form of the Good, source of all being and knowledge. The freed prisoner's return to the cave represents the philosopher's duty to help others, even at personal cost.

H3: The Republic

Plato's masterpiece explores justice, both in the individual and in society. He constructs an ideal state with three classes: rulers (philosopher-kings), guardians (warriors), and producers (workers). Justice occurs when each part does its proper work.

The soul has a parallel structure: reason (should rule), spirit (should enforce reason's commands), and appetite (should be ruled). Justice in the individual is harmony among these parts.

Plato argues that philosophers should be kings because only they know the Forms, especially the Form of the Good, and can govern wisely. This "philosopher-king" ideal has been enormously influential, though often criticized as authoritarian.

H3: Other Dialogues

Phaedo: Socrates' last conversation, arguments for immortality of the soul. Symposium: Speeches about love (eros), culminating in Diotima's ladder of love ascending to Form of Beauty. Phaedrus: Love, rhetoric, and the soul as charioteer. Meno: Can virtue be taught? Includes famous slave-boy demonstration of recollection. Timaeus: Plato's cosmology, creation of universe by divine craftsman (demiurge).

H3: Logic and Metaphysics

Aristotle systematized logic, developing the syllogism: "All men are mortal; Socrates is man; therefore Socrates is mortal." His Organon (collection of logical works) dominated Western logic for 2,000 years.

He rejected Plato's Theory of Forms. Forms are not separate but exist in things. Substance is the primary reality—individual things like this horse or this person. He analyzed change through four causes:

Material cause: what something is made of (bronze for a statue)

Formal cause: the form or essence (shape of the statue)

Efficient cause: the agent of change (the sculptor)

Final cause: the purpose or end (to honor someone)

This teleological view—everything has a purpose—influenced science and theology for centuries.

H3: Physics and Psychology

Aristotle's physics dominated until Newton. He distinguished natural motion (objects seeking their natural place) and violent motion (imposed by force). The cosmos has a sublunary realm (change, generation, corruption) and celestial realm (unchanging, eternal, moved by unmoved movers).

His psychology: The soul (psyche) is the form of the body. Plants have nutritive souls, animals have sensitive souls, humans have rational souls. Knowledge comes through sense experience—the mind is initially a blank slate (tabula rasa).

H3: Ethics: Nicomachean Ethics

For Aristotle, the highest good is eudaimonia—flourishing or living well. This is achieved through virtue (aretē). Virtue is the mean between extremes: courage is the mean between cowardice and recklessness; generosity between stinginess and profligacy.

Virtues are developed through practice—we become just by doing just acts. Practical wisdom (phronēsis) is needed to discern the mean in particular situations. The ideal is the great-souled person (megalopsychos) who has all virtues and proper self-esteem.

The life of contemplation (theōria) is the highest, most divine form of happiness—as close as humans can come to the activity of God.

H3: Politics and Poetics

"Man is by nature a political animal." Humans achieve full potential only in community. Politics studies the best form of government—Aristotle examined constitutions of 158 Greek city-states. He identified good forms (monarchy, aristocracy, polity) and corrupt forms (tyranny, oligarchy, democracy).

In Poetics, he analyzed tragedy, introducing concepts of catharsis (purgation of emotions), hamartia (tragic flaw), and peripeteia (reversal of fortune). His analysis remains influential in literary theory.

H3: Stoicism

Founded by Zeno of Citium (c. 334-262 BCE). The universe is governed by divine reason (logos). Humans should live in accordance with nature, accepting what happens with equanimity. The only true good is virtue; externals (wealth, health, reputation) are indifferent (adiaphora).

Key doctrines: dichotomy of control (focus on what's up to us). Emotions result from false judgments; the sage achieves apatheia—freedom from destructive passions. Roman Stoics: Seneca, Epictetus, Marcus Aurelius (Meditations).

H3: Epicureanism

Founded by Epicurus (341-270 BCE). Pleasure (hedone) is the highest good—but pleasure understood as absence of pain (aponia) and tranquility (ataraxia). Pursue simple pleasures, avoid excess. Friendship is essential to happiness.

Adopted Democritus' atomism—soul atoms disperse at death, so no afterlife to fear. Gods exist but don't intervene, so no divine punishment to fear. "Death is nothing to us"—when we exist, death is not; when death comes, we don't exist. Lucretius' De Rerum Natura preserved Epicureanism.

H3: Skepticism

Pyrrhonian skepticism (Pyrrho, c. 360-270 BCE) argued we should suspend judgment (epochē) because equally convincing arguments can be given for any position. Suspension leads to tranquility (ataraxia).

Academic skepticism (Arcesilaus, Carneades) claimed nothing can be known, though probability can guide action. Sextus Empiricus compiled arguments for skepticism.

H3: Cynicism

Founded by Antisthenes, famous through Diogenes of Sinope (c. 412-323 BCE). Live according to nature, rejecting conventions, possessions, and social status. Diogenes lived in a barrel, owned only a cloak and staff. When Alexander the Great offered him anything, he replied "Stand out of my sunlight."

H3: St. Augustine (354-430)

Augustine synthesized Christianity with Neoplatonism. In Confessions, he explored memory, time, and his conversion. He argued that knowledge requires divine illumination—we see eternal truths in the light of God.

On the problem of evil: evil is privation of good, not a positive force. Free will explains moral evil. In City of God, he distinguished earthly city (self-love) from heavenly city (love of God). His theology dominated Western Christianity until Aquinas.

H3: St. Anselm (1033-1109)

Developed the ontological argument for God's existence. God is "that than which nothing greater can be conceived." Even the fool who denies God has this concept. But that which exists in reality is greater than that which exists only in the mind. Therefore, God must exist in reality.

Gaunilo objected: by this logic, we could prove the existence of a perfect island. Kant later argued existence is not a predicate.

H3: St. Thomas Aquinas (1225-1274)

Aquinas synthesized Aristotle with Christianity in his Summa Theologica. He offered Five Ways to prove God's existence:

1. Argument from motion (unmoved mover)

2. Argument from causation (uncaused cause)

3. Argument from contingency (necessary being)

4. Argument from degrees of perfection

5. Argument from design (teleological)

He distinguished faith and reason—some truths (Trinity) are known only through revelation, others (God's existence) can be known by reason. His natural law ethics influenced Catholic moral theology.

H3: Islamic and Jewish Philosophy

Avicenna (Ibn Sina, 980-1037): Developed distinction between essence and existence. The necessary existent (God) has essence identical with existence; contingent beings receive existence from God.

Averroes (Ibn Rushd, 1126-1198): Commentator on Aristotle, argued for harmony between philosophy and religion. Influenced Latin Averroism.

Maimonides (1135-1204): Jewish philosopher, Guide for the Perplexed, attempted to reconcile Aristotle with Jewish theology.

William of Occam (c. 1287-1347): Occam's razor—entities should not be multiplied beyond necessity. Argued for nominalism—universals are mere names, not real entities.

H3: René Descartes (1596-1650)

"Father of Modern Philosophy." Meditations on First Philosophy (1641) foundational text. Method of doubt—systematically doubt everything until find indubitable foundation. Can doubt senses (illusions, dreams), even mathematics (evil demon might deceive).

Cogito ergo sum—"I think, therefore I am." Even if deceived, must exist to be deceived. Foundation for knowledge. Clear and distinct perceptions criterion. Proofs for God's existence—trademark argument, ontological. God guarantees reliability of clear and distinct perceptions.

Mind-body dualism: Mind (thinking substance) distinct from body (extended substance). Interaction problem—how do they interact? (pineal gland). Legacy: foundationalism, subject-centered philosophy.

H3: Baruch Spinoza (1632-1677)

Ethics (1677) written in geometric style—definitions, axioms, propositions. Substance—one infinite substance (God or Nature) with infinite attributes. Humans know two: thought and extension. Pantheism—God identical with nature.

Determinism—everything follows necessarily from God's nature. Humans think themselves free because conscious of actions but ignorant of causes. Conatus—each thing strives to persist. Emotions based on inadequate ideas; reason leads to adequate ideas, freedom, blessedness. Intellectual love of God—highest good.

H3: Gottfried Wilhelm Leibniz (1646-1716)

Monadology—reality composed of monads (simple substances, windowless, perceiving universe from perspective). Pre-established harmony—God synchronized monads so they appear to interact.

Principle of sufficient reason—nothing without reason. Identity of indiscernibles—no two distinct things exactly alike. Best of all possible worlds—God chose best combination (satirized in Candide). Innate ideas—mind like veined marble, not blank slate. Calculus (independently of Newton).

H3: John Locke (1632-1704)

Essay Concerning Human Understanding (1689) attacks innate ideas. Mind at birth tabula rasa (blank slate). All ideas from experience: sensation (external) and reflection (internal). Simple ideas combine into complex.

Primary qualities (solidity, extension, figure, motion)—inseparable from body. Secondary qualities (color, sound, taste)—powers to produce sensations, not in objects themselves. Knowledge—perception of agreement/disagreement of ideas.

Political philosophy—Two Treatises of Government: natural rights (life, liberty, property), consent, limited government, right to revolution. Influenced American founders.

H3: George Berkeley (1685-1753)

Idealism—esse est percipi (to be is to be perceived). Material substance doesn't exist—only minds and ideas. Objects are collections of ideas perceived by minds. When not perceived by finite minds, perceived by God, ensuring continuity.

Primary qualities also mind-dependent—no abstraction possible. Attack on abstract ideas, materialism. Three Dialogues between Hylas and Philonous defends idealism. Bishop of Cloyne.

H3: David Hume (1711-1776)

Most radical empiricist. Treatise of Human Nature (1739)—attempt to introduce experimental method into moral subjects. Impressions (lively) and ideas (faint copies). All ideas derive from impressions.

Relations of ideas (a priori, necessary) vs matters of fact (a posteriori, contingent). Causation—not observable; we perceive constant conjunction, feel expectation, project necessity. Problem of induction—no rational justification for expecting future to resemble past.

Self—bundle of perceptions, no enduring self. Skepticism about miracles, religion. Is-ought problem—cannot derive ought from is. Dialogues Concerning Natural Religion critiques design argument.

H3: Critique of Pure Reason

Kant's "Copernican revolution" in philosophy: objects conform to our cognition, not vice versa. We can know a priori that objects will conform to our forms of intuition (space and time) and categories of understanding (causality, substance, etc.).

Synthetic a priori judgments: Judgments that are both informative (synthetic) and known independently of experience (a priori)—e.g., mathematics, metaphysics foundations. How are they possible? Kant's central question.

Transcendental aesthetic: Space and time are forms of intuition—necessary conditions for experience, not properties of things in themselves.

Transcendental analytic: Categories (causality, substance, etc.) are concepts of understanding that structure experience.

Phenomena vs. noumena: We know only phenomena (things as they appear), not noumena (things in themselves).

H3: Critique of Practical Reason

Moral philosophy based on reason, not consequences. The good will is the only unconditional good. Moral law is discovered through reason, not derived from experience.

Categorical imperative (formulations):

"Act only according to that maxim whereby you can at the same time will that it should become a universal law." (Universalizability)

"Act in such a way that you treat humanity, whether in your own person or in the person of any other, never merely as a means, but always at the same time as an end." (Humanity formulation)

Kingdom of ends: Ideal community where all are both legislators and subjects.

Postulates of practical reason: Freedom, immortality, God—necessary for morality though not provable.

H3: Critique of Judgment

Bridges pure and practical reason through judgments of taste and teleology. The beautiful pleases universally without concept—we feel that others should agree. The sublime involves awe at vastness or power beyond comprehension. Teleological judgment sees nature as purposive, guiding scientific inquiry.

H3: Legacy

Kant synthesized rationalism and empiricism, fundamentally reshaping philosophy. German idealism (Fichte, Schelling, Hegel) developed his insights. His ethics influenced Rawls, Habermas. His epistemology set terms for subsequent debate. Perpetual Peace essay envisioned international cooperation.

H3: Søren Kierkegaard (1813-1855)

"Father of Existentialism." Attacked Hegelian system, abstract thinking. Emphasis on individual existence, subjective truth. Three stages: aesthetic (pleasure), ethical (duty), religious (faith).

Fear and trembling—Abraham's faith beyond ethical. Concept of anxiety—freedom's possibility. Sickness unto death—despair. Leap of faith—not rational but passionate commitment. Attack on Christendom—authentic Christianity requires risk.

H3: Friedrich Nietzsche (1844-1900)

Critique of morality, religion, philosophy. "God is dead"—decline of Christian morality. Genealogy of Morals—master morality (good/bad) vs slave morality (good/evil). Ressentiment—slave morality inverts values.

Will to power—fundamental drive, not just survival. Übermensch (Overman)—creator of new values, beyond good and evil. Eternal recurrence—would you live life over infinitely? Amor fati—love of fate.

Perspectivism—no objective facts, only interpretations. Thus Spoke Zarathustra—poetic/philosophical. Influenced existentialism, postmodernism, psychology.

H3: Jean-Paul Sartre (1905-1980)

"Existence precedes essence"—humans first exist, then define themselves through choices. No predetermined human nature. Radical freedom—condemned to be free. Bad faith (mauvaise foi)—denying freedom by pretending determined.

Being and Nothingness—phenomenological ontology. For-itself (consciousness) vs in-itself (things). Anguish—awareness of freedom. No exit—"Hell is other people." Existentialism is a Humanism—defends existentialism as optimistic, empowering.

H3: Albert Camus (1913-1960)

Often associated with existentialism but rejected label. Myth of Sisyphus—the absurd: conflict between human desire for meaning and universe's indifference. Sisyphus symbolizes human condition—endless futile labor, but finds meaning in struggle.

The Stranger—Meursault detached, society demands conventional emotion. The Plague—solidarity in facing absurd. The Rebel—rebellion against absurdity and oppression.

H3: Gottlob Frege (1848-1925)

Founder of analytic philosophy. Distinguished sense (Sinn) and reference (Bedeutung). "The morning star" and "the evening star" have same reference (Venus) but different sense. Developed predicate logic, foundation of modern logic.

H3: Bertrand Russell (1872-1970)

With Whitehead, Principia Mathematica attempted to derive mathematics from logic. Theory of descriptions—analyzing definite descriptions ("the present King of France") solves philosophical puzzles. Logical atomism—world consists of logical atoms. Influential on logic, epistemology, social philosophy.

H3: G.E. Moore (1873-1958)

Defended common sense against skepticism. "Here is one hand" argument. Principia Ethica—identified the "naturalistic fallacy," argued goodness is simple, non-natural property known by intuition.

H3: Logical Positivism

Vienna Circle (Schlick, Carnap, Neurath). Verification principle—meaningful statements must be empirically verifiable. Rejected metaphysics as meaningless. Influenced by Wittgenstein's Tractatus. Ayer's Language, Truth, and Logic popularized logical positivism in English.

H3: Early Wittgenstein: Tractatus Logico-Philosophicus

The world is the totality of facts, not things. Language pictures facts through logical form. Propositions are truth-functions of elementary propositions. What can be said at all can be said clearly; what cannot be spoken about must be passed over in silence.

The limits of language are the limits of my world. Ethics, aesthetics, religion are transcendental—cannot be said, only shown. The book's structure (1, 1.1, 1.11...) reflects logical hierarchy. Wittgenstein believed he had solved all philosophical problems.

H3: Later Wittgenstein: Philosophical Investigations

Rejected his earlier views. Meaning is use—words get meaning from how they're used in language games. Family resemblances—concepts don't have essential features but overlapping similarities. Language is a form of life, embedded in practices.

Private language argument—a private language (sensations only I can know) is impossible because language requires public criteria. Philosophy is therapy—dissolves confusions rather than solving problems. "Don't think, but look!"

H3: Confucius (Kong Qiu, 551-479 BCE)

China's most influential philosopher. His teachings compiled in Analects (Lunyu). Focus on ethics, social harmony, not metaphysics or religion. Key concepts:

Ren (仁): Benevolence, humaneness, perfect virtue. The highest Confucian virtue, involving love for others and treating them with humanity.

Li (禮): Ritual propriety, rites, customs. Proper behavior in social contexts, from daily etiquette to state ceremonies. Li shapes character and maintains social order.

Xiao (孝): Filial piety—respect and care for parents and ancestors. Foundation of all virtue.

Junzi (君子): The exemplary person—moral ideal cultivated through learning and practice.

H3: Five Relationships

Society consists of five key relationships, each with reciprocal duties:

1. Ruler-subject: benevolence from ruler, loyalty from subject

2. Parent-child: kindness from parent, filial piety from child

3. Husband-wife: righteous conduct from husband, obedience from wife

4. Elder-younger: gentility from elder, respect from younger

5. Friend-friend: mutual faithfulness

When each person fulfills their role, society harmoniously functions.

H3: Mencius (372-289 BCE)

Second most important Confucian. Argued human nature is good—everyone has sprouts of virtue (compassion, shame, respect, right-wrong). These must be cultivated through education and practice. Developed concept of right to revolution—if ruler fails to be virtuous, people may replace him.

H3: Xunzi (310-235 BCE)

Countered Mencius—human nature is evil, goodness results from conscious activity. Ritual (li) and education are necessary to transform human nature. Influenced Legalism.

H3: Laozi (Lao Tzu) and the Dao De Jing

Traditional author of Dao De Jing (Tao Te Ching), probably compiled around 4th-3rd century BCE. The book's 81 short chapters present Daoist philosophy in poetic, paradoxical form.

Dao (道): The Way—ultimate reality, source of all things, beyond conceptualization. "The Dao that can be spoken is not the eternal Dao." It is nameless, formless, yet gives rise to everything.

De (德): Virtue, power—the manifestation of Dao in individual things.

Wu wei (無為): Non-action, effortless action—acting in harmony with Dao, without forcing or striving. "Do nothing, and nothing is left undone."

Pu (樸): Uncarved block—simplicity, natural state before social conditioning.

H3: Zhuangzi (Chuang Tzu, 369-286 BCE)

Zhuangzi's book uses humor, paradox, and stories to convey Daoist insights. Famous story: he dreamed he was a butterfly, and upon waking, wasn't sure if he was Zhuangzi who dreamed butterfly or butterfly dreaming Zhuangzi.

Relativism of perspectives—no absolute standard; what's right from one perspective is wrong from another. Freedom through going beyond conventional distinctions. Uselessness as usefulness—the useless tree survives while useful ones are cut down.

H3: The Buddha (Siddhartha Gautama, c. 5th century BCE)

Born a prince, encountered old age, sickness, and death, renounced luxury, sought enlightenment through asceticism and meditation. Attained enlightenment under bodhi tree, taught until death at 80.

Four Noble Truths

1. Life is suffering (dukkha)—birth, aging, sickness, death, separation from loved ones, not getting what we want.

2. Suffering arises from craving (tanha)—desire for sensual pleasures, existence, non-existence.

3. Suffering ceases when craving ceases—nirvana, extinction of desire.

4. The Eightfold Path leads to cessation of suffering.

H3: The Eightfold Path

Divided into wisdom, ethical conduct, and mental discipline:

Wisdom: Right view (understanding Four Noble Truths), Right intention (renunciation, goodwill, harmlessness).

Ethical conduct: Right speech (no lying, gossip, harsh words), Right action (no killing, stealing, sexual misconduct), Right livelihood (honest work).

Mental discipline: Right effort (cultivate wholesome states), Right mindfulness (awareness of body, feelings, mind, phenomena), Right concentration (meditative absorption).

H3: Key Buddhist Concepts

Anatman (no-self): No permanent, unchanging self. What we call "self" is five aggregates (skandhas): form, feeling, perception, mental formations, consciousness. All are impermanent and dependently arisen.

Pratityasamutpada (dependent origination): All phenomena arise in dependence on causes and conditions. Nothing exists independently.

Karma and rebirth: Intentional actions have consequences, shaping future rebirths. Goal is liberation from cycle of rebirth (samsara).

H3: Major Buddhist Schools

Theravada ("Way of Elders"): Oldest surviving school, dominant in Sri Lanka, Southeast Asia. Focus on monastic practice, ideal of arhat (enlightened one).

Mahayana ("Great Vehicle"): Developed in India, spread to East Asia. Ideal of bodhisattva—one who postpones nirvana to help all beings. Includes Zen (Chan), Pure Land, Tibetan Buddhism.

Madhyamaka (Nagarjuna): Emptiness (shunyata) of all phenomena—everything is empty of inherent existence, dependently arisen.

Yogacara: Mind-only (cittamatra)—reality is constructed by consciousness.

H3: Ontology

Substance: What exists independently. Aristotle: primary substances (individuals) vs secondary (species). Descartes: thinking substance (mind) vs extended (body). Spinoza: one substance (God/Nature). Leibniz: infinitely many substances (monads).

Universals vs particulars: Do properties (redness, justice) exist independently? Realism (Plato)—universals exist abstractly. Nominalism—only particular things, universals just names. Conceptualism—universals exist only in mind.

Possibility and necessity: Modal metaphysics. Possible worlds (Leibniz, Lewis). Essence—necessary properties. Accidents—contingent properties.

H3: Causation and Free Will

Causation: Hume's regularity theory—causation just constant conjunction. Kant—causality necessary category for understanding. Mackie—INUS conditions. Counterfactual theories—c causes e if without c, e wouldn't occur. Probabilistic causation—c raises probability of e.

Free will: Determinism—every event caused. Libertarianism—free will incompatible with determinism, we have free will. Hard determinism—incompatibilism, no free will. Compatibilism—free will compatible with determinism (Hume, Mill, Frankfurt).

H3: Time and Space

A-theory (tensed): Past, present, future real, present privileged. B-theory (tenseless): All times equally real, tense illusion (McTaggart). Presentism: Only present exists. Eternalism: Past, present, future all exist. Growing block: Past and present exist, future not.

Space: Absolute (Newton) vs relational (Leibniz). Kant: space is form of intuition.

H3: Mind-Body Problem

Dualism: Mind and body distinct (Descartes, interaction problem). Idealism: Only mind exists (Berkeley). Materialism: Only matter exists. Behaviorism: Mental states behavioral dispositions. Identity theory: Mental states identical with brain states. Functionalism: Mental states functional roles. Property dualism: Mental properties non-physical. Panpsychism: Consciousness fundamental.

H3: What is Knowledge?

Plato's definition: justified true belief (JTB). S knows that p if: p true, S believes p, S justified in believing p. Gettier problems (1963)—counterexamples where JTB but not knowledge (justified true belief by luck).

Responses: strengthen justification (no false lemmas), causal theory, reliabilism, virtue epistemology. Some argue knowledge isn't JTB—contextualism, invariantism.

H3: Skepticism

Pyrrhonian skepticism: Suspend judgment (epochē) achieve ataraxia. Academic skepticism: Knowledge impossible. Cartesian skepticism: Methodological doubt, evil demon. Brain-in-vat hypothesis.

Responses: Moore's proof of external world, contextualism, relevant alternatives, reliabilism.

H3: Sources of Knowledge

Perception: Sensory experience. Memory: Retains knowledge. Introspection: Knowledge of own mental states. Reason: A priori knowledge. Testimony: Knowledge from others.

A priori vs a posteriori: A priori—independent of experience (logic, mathematics). A posteriori—dependent on experience (empirical science). Kant: synthetic a priori (mathematics, metaphysics). Quine: analytic-synthetic distinction problematic.

H3: Justification

Foundationalism: Beliefs based on foundational beliefs (sense data, self-evident truths). Coherentism: Beliefs justified by coherence with other beliefs. Reliabilism: Belief justified if produced by reliable process. Evidentialism: Justification determined by evidence. Internalism: Justification accessible to subject. Externalism: Justification can be external (reliabilism).

H3: Normative Ethics

Consequentialism: Rightness depends on consequences. Utilitarianism (Bentham, Mill)—maximize happiness (hedonic calculus). Act vs rule utilitarianism. Problems: demandingness, justice, calculation.

Deontology: Rightness depends on duty, rules (Kant). Categorical imperative—universalizability, humanity as end. W.D. Ross—prima facie duties. Scanlon—contractualism.

Virtue ethics: Rightness depends on character (Aristotle). Eudaimonia—flourishing. Cardinal virtues: wisdom, justice, courage, temperance. Contemporary revival (MacIntyre, Hursthouse).

Care ethics: Emphasizes relationships, care (Gilligan, Noddings).

H3: Metaethics

Moral realism: Moral facts objective (Railton, Boyd). Naturalism—moral facts natural properties. Non-naturalism (Moore)—"open question argument," intuitionism.

Moral anti-realism: No moral facts. Error theory (Mackie)—moral claims systematically false. Emotivism (Ayer, Stevenson)—moral language expresses emotion. Prescriptivism (Hare)—moral language prescribes. Projectivism (Blackburn)—project attitudes onto world.

Constructivism (Rawls, Korsgaard)—moral principles constructed by rational agents.

H3: Applied Ethics

Bioethics: Abortion, euthanasia, genetic engineering, research ethics. Business ethics: Corporate responsibility, whistleblowing. Environmental ethics: Value of nature, animal rights (Singer, Regan). Just war theory: Jus ad bellum, jus in bello. Information ethics: Privacy, AI ethics. Neuroethics: Ethical issues in neuroscience.

H3: Deductive Logic

Deductive argument—premises guarantee conclusion. Valid—if premises true, conclusion must be true. Sound—valid + true premises.

Syllogism (Aristotle): All men are mortal; Socrates is man; therefore Socrates mortal. Categorical propositions: All S are P, No S are P, Some S are P, Some S are not P.

Propositional logic: Connectives: and (∧), or (∨), not (¬), if-then (→). Truth tables. Modus ponens: P→Q, P, therefore Q. Modus tollens: P→Q, ¬Q, therefore ¬P.

Predicate logic: Quantifiers: ∀ (all), ∃ (some). First-order logic standard.

H3: Inductive Logic

Inductive argument—premises make conclusion probable. Strong/weak, cogent/not cogent. Induction by enumeration—observing many instances. Statistical syllogism. Analogy. Inference to best explanation (abduction).

Problem of induction (Hume)—no rational justification for expecting future to resemble past.

H3: Fallacies

Formal fallacies: Error in logical form. Affirming the consequent: P→Q, Q, therefore P. Denying the antecedent: P→Q, ¬P, therefore ¬Q.

Informal fallacies: Error in content. Ad hominem—attack person. Straw man—misrepresent. Appeal to authority—irrelevant authority. Appeal to popularity—many believe. False dilemma—limited options. Slippery slope—exaggerated consequences. Begging the question—assuming what to prove. Hasty generalization—small sample. Post hoc ergo propter hoc—false cause.

H3: Formal Systems

Axiomatic systems—axioms, rules of inference, theorems. Consistency—no contradictions. Completeness—all truths provable. Decidability—algorithm for determining truth. Gödel's incompleteness theorems—arithmetic cannot be both consistent and complete.