Philosophy is the rational, abstract, and methodical investigation of reality as a whole and of fundamental dimensions of human experience, a usage rooted in the Greek philosophia, “love of wisdom,” and applied across many civilizations’ intellectual histories. According to Encyclopaedia Britannica, philosophy centrally examines reality, knowledge, and value, and has been articulated in multiple branches and traditions since antiquity. Britannica.

Historical development

The discipline emerged in written form in ancient Greece with figures such as Socrates, Plato, and Aristotle, while parallel and independent traditions formed in classical China and India. Britannica characterizes Western philosophy as developing from the Greek world through Hellenistic schools, medieval scholasticism, the Renaissance, and modern and contemporary movements. Britannica. In China, philosophical inquiry spanned classical Confucian, Daoist, and other schools in the 6th–3rd centuries BCE, then evolved through Neo-Daoist/Buddhist and Neo-Confucian periods before modern transformations. Britannica. Indian philosophy comprised orthodox (Nyāya, Vaiśeṣika, Sāṃkhya, Yoga, Mīmāṃsā, Vedānta) and unorthodox (Buddhist, Jain) systems with distinct logical and metaphysical programs across prelogical, logical, and ultralogical periods. Britannica. In the Islamic world (9th–12th centuries), philosophers such as al-Kindī, al-Fārābī, Avicenna, and Averroës engaged Aristotelian and Neoplatonic thought in Arabic, shaping later medieval scholasticism in Latin Christendom. Britannica; Britannica. Medieval European philosophy integrated Greek sources with Christian theology, culminating in scholastic methods of lecture and disputation at universities in Paris and Oxford. Britannica; Britannica.

Key figures often cited as formative include Socrates, whose life and trial shaped ethical inquiry and the “examined life”; Aristotle, whose treatises in logic, metaphysics, ethics, and natural philosophy set enduring agendas; Immanuel Kant, whose “critical philosophy” reframed metaphysics and ethics in the 18th century; and Confucius, whose teachings on ritual, virtue, and governance defined much of East Asian thought. Britannica; Britannica; Britannica; Britannica.

Major branches

• –Metaphysics: the study of what exists and of the ultimate structure of reality, including categories such as substance, properties, space–time, modality, and mind–body relations. The Stanford Encyclopedia of Philosophy (SEP) characterizes contemporary metaphysics as addressing problems from modality and possible worlds to mental causation and material constitution. Stanford Encyclopedia of Philosophy; Britannica.
• –Epistemology: inquiry into the nature, sources, and limits of knowledge, including justification, skepticism, perception, memory, reason, and testimony. SEP’s overview traces epistemology from Plato to contemporary debates about reliability and the analysis of knowledge. Stanford Encyclopedia of Philosophy; Britannica.
• –Ethics: study of value and conduct, encompassing normative ethics (e.g., deontology, consequentialism, virtue theory), metaethics, and applied ethics. SEP surveys normative theories and contrasts ethics with narrower conceptions of morality. Stanford Encyclopedia of Philosophy; Britannica.
• –Logic: analysis of valid inference and argument structure, often via formal languages and proof systems; classical first‑order logic remains a benchmark, though many nonclassical systems are studied. SEP characterizes a logic as a language with deductive system and semantics, highlighting meta-theorems such as soundness and completeness. Stanford Encyclopedia of Philosophy; Britannica.
• –Aesthetics and philosophy of art: investigation of beauty, aesthetic experience, and artistic value, treated historically from Plato and Aristotle through modern debates about interpretation and ontology. Britannica.
• –Political philosophy and philosophy of law: analysis of authority, justice, rights, and institutions from classical sources to modern contractarian and critical traditions. Britannica; Britannica.
• –Philosophy of science: clarification of scientific concepts, methods, explanation, and theory change, addressing ontological commitments and epistemic warrant. Britannica; Stanford Encyclopedia of Philosophy.

Methods and tools

Philosophical work relies on conceptual analysis, the construction and evaluation of arguments, use of formal logic, and the careful deployment of examples and thought experiments to test principles and definitions. Britannica contrasts analytic tendencies toward clarity and part–whole analysis with synthetic tendencies toward systematic unity, reflecting long-standing methodological pluralism in the discipline. Britannica. Formal methods employ languages, proof systems, and model-theoretic semantics to characterize validity and consequence, as detailed in SEP’s account of classical logic. Stanford Encyclopedia of Philosophy. In epistemology and ethics alike, philosophers analyze sources of knowledge (perception, memory, testimony, reason) and patterns of justification, often balancing considered judgments and theoretical principles. Stanford Encyclopedia of Philosophy; Stanford Encyclopedia of Philosophy.

Major traditions and schools

In contemporary classification, Anglophone departments often distinguish between Analytic Philosophy, with its emphasis on clarity, argument, and language, and Continental philosophy, a broad term for diverse European traditions including phenomenology, existentialism, structuralism, and deconstruction. The Internet Encyclopedia of Philosophy (IEP) presents analytic philosophy’s 20th‑century development from Moore and Russell through logical positivism and post‑positivist turns, while Britannica’s overview of continental philosophy highlights movements from Kant to 20th‑century currents. Internet Encyclopedia of Philosophy; Britannica.

Beyond Europe, long-standing traditions continue to shape global philosophy: Confucian ethics and statecraft in East Asia, Indian systems ranging from Nyāya logic to Vedānta metaphysics, and Islamic falsafa and kalām that mediated classical Greek philosophy and influenced medieval Latin thought. Britannica; Britannica; Britannica. Scholarly treatments also document African philosophical currents, including Bantu thought and concepts such as ubuntu, developed within decolonizing and intercultural frameworks. Britannica.

Canonical figures and texts

• –Socrates (c. 470–399 BCE) is presented by ancient sources as exemplifying a life of inquiry and dialectical method, culminating in his trial and death at Athens. Britannica.
• –Aristotle (384–322 BCE) authored foundational works in logic (the Organon), metaphysics, ethics, and natural philosophy that set terms for subsequent inquiry. Britannica.
• –Immanuel Kant (1724–1804) reoriented metaphysics and ethics via his critiques of reason and conceptions of autonomy and the moral law. Britannica.
• –Confucius (551–479 BCE) taught a virtue-ethical program centered on ren, li, and righteous governance, influential throughout East Asia. Britannica.

Standard reference works used by scholars include The Cambridge Dictionary of Philosophy and comprehensive encyclopedias such as SEP and IEP, which commission peer‑reviewed entries maintained by subject experts. Stanford University Philosophy Department; Internet Encyclopedia of Philosophy.

Contemporary areas and applications

Contemporary philosophy addresses specialized subfields—philosophy of mind, language, mathematics, law, biology, religion, and technology—while applied ethics engages bioethics, environmental ethics, and AI ethics using normative and conceptual analysis. These areas draw on and extend core branches such as Epistemology, Metaphysics, and logic to clarify assumptions, evaluate arguments, and guide decision-making in science, policy, and culture. Britannica; Britannica; Stanford Encyclopedia of Philosophy.

Pedagogy and institutions

From medieval disputations to modern departments, philosophy has been taught as a discipline emphasizing argument, clarity, and rigor. Britannica’s histories of medieval scholasticism and Western philosophy describe the institutionalization of philosophical study in universities and its ongoing diversification into global traditions and new research programs. Britannica; Britannica. SEP and IEP exemplify contemporary, open‑access reference infrastructures that curate evolving scholarship through expert editorial processes. Stanford University Philosophy Department; Internet Encyclopedia of Philosophy.

Further reading (selected reference works)

• –The Cambridge Dictionary of Philosophy provides concise, scholarly coverage of terms, figures, and schools across subfields. (book://Robert Audi|The Cambridge Dictionary of Philosophy|Cambridge University Press|1999).
• –Bertrand Russell’s synthetic survey remains a touchstone in intellectual history for Western traditions. (book://Bertrand Russell|A History of Western Philosophy|George Allen & Unwin|1945).
• –Fung Yu‑lan’s overview is a classic introduction to Chinese philosophical development. (book://Fung Yu-lan|A Short History of Chinese Philosophy|Free Press|1948).
• –A Sourcebook in Indian Philosophy anthologizes seminal texts across schools. (book://Sarvepalli Radhakrishnan; Charles A. Moore|A Sourcebook in Indian Philosophy|Princeton University Press|1957).
• –The Cambridge Companion to Arabic Philosophy surveys figures and themes in the Islamic tradition. (book://Peter Adamson; Richard C. Taylor|The Cambridge Companion to Arabic Philosophy|Cambridge University Press|2005).