The word ‘philosophy’ is derived from ancient Greek—a combination of the words philos (“loving, friend of”) and sophía (“wisdom”)—and roughly translates to “love of wisdom.” Generally, there are five major branches of philosophy: metaphysics, epistemology, ethics, logic, and aesthetics. Each branch focuses on specific areas of study, though they often overlap.

These branches and their areas of study are as follows:

Metaphysics: The study of the fundamental nature of reality, existence, and being.
•Metaphysics asks: What is ultimately real? What does it mean for something to exist? Why is there something rather than nothing? What is time?
•Notable metaphysicians: Plato, Aristotle, Gottfried Leibniz, George Berkeley, Immanuel Kant, Baruch Spinoza, G.W.F. Hegel
•Famous Thought Experiment: The Ship of Theseus

Epistemology: The study of the nature, origin, and limitations of knowledge.
•Epistemology asks: What can we know? What is truth? How are our beliefs justified? What are the limits of knowledge? What are the sources of knowledge? Can we trust our senses?
•Notable epistemologists: Plato, Socrates, George Berkeley, René Descartes, David Hume, John Locke, Immanuel Kant, Bertrand Russell, Edmund Gettier
•Famous Thought Experiment: The Cow in the Field (Gettier Problem)

Ethics: The study of morality, moral values, and principles.
•Ethics asks: How should we live? What makes an action morally right or wrong? Are there objective moral truths? Is it ever ok to lie? Is war ever justified? Should everyone have equal rights? Should capital punishment exist? Can AI make moral decisions?
•Notable ethicists: Socrates, Plato, Aristotle, Immanuel Kant, John Stuart Mill, David Hume, Thomas Aquinas, Thomas Hobbes, Friedrich Nietzsche, John Rawls
•Famous Thought Experiment: The Trolley Problem

Logic: The study of reasoning and argumentation.
•Logic asks: What makes reasoning good or bad? What makes an argument valid/sound? What is a contradiction? What does “if…then” mean?
•Notable logicians: Aristotle, Ludwig Wittgenstein, Gottlob Frege, Kurt Gödel, George Boole, Gottlob Frege, Bertrand Russell
•Famous Paradox: The Liar Paradox

Aesthetics: The study of beauty and art.
•Aesthetics asks: What is beauty and art? What makes art good? Why does art matter? Is beauty subjective? Does the artist’s intention dictate the meaning of a work?  How does culture shape aesthetic preferences?
•Notable philosophers of aesthetics: Plato, Aristotle, David Hume, G.W.F. Hegel, Friedrich Nietzsche, Edmund Burke, Immanuel Kant
•Famous Thought Experiment: The Perfect Forgery

As mentioned previously, many of these branches overlap, and many notable philosophers are known for their contributions to multiple branches.

Under each of these five main branches of philosophy, you will find an assortment of sub-branches, including (but not limited to):

Social Philosophy: The study of social institutions, societal structures, and how society should be governed. Ex: How should we share wealth, power, and duties?
(Often overlaps with ethics)
•Famous Thought Experiment: The Veil of Ignorance

Political Philosophy: The study of government, justice, liberty, and rights. Ex: Why do we need a government?
(Often overlaps with ethics)
•Famous Thought Experiment: The State of Nature (Hobbes)

Philosophy of Mind: The study of the nature of the mind. Ex: What is it like to be a different creature, such as a bat?
(Often overlaps with metaphysics, epistemology, and ethics)
•Famous Thought Experiment: Mary’s Room

Philosophy of Religion: The study of the nature of religion. Ex: If God is all-knowing, all-powerful, and perfectly good, why does evil exist?
(Often overlaps with metaphysics, epistemology, and ethics)
•Famous Thought Experiment: Pascal’s Wager

Philosophy of Science: The study of the nature of science. Ex: What is the difference between science and pseudoscience?
(Often overlaps with metaphysics and epistemology)
•Famous Thought Experiment: The Problem of Induction

Philosophy of Language: The study of the nature of language. Ex: How does language convey meaning?
(Often overlaps with logic, epistemology, and metaphysics)
•Famous Thought Experiment: The Beetle in a Box