What Is Philosophy? Branches & Methods

Core Philosophical Problems

Course 3 · Chapter 1 · What Is Philosophy? Branches & Methods

Courses 1 and 2 told philosophy's own story chronologically — one era, one tradition, one thinker at a time. This course does something different: it takes the full cast those twenty chapters already introduced and organizes them by question instead of by century, cutting straight across two and a half thousand years in a single chapter whenever the topic calls for it.

What "Philosophy" Actually Means

The word comes from the Greek philosophia — philos ("loving" or "friend of") plus sophia ("wisdom"): love of wisdom. A popular story credits Pythagoras with coining the term himself, deliberately choosing to call himself a "lover of wisdom" rather than claiming the grander title of sophos, "wise man" outright.

An Honest Uncertainty — that Pythagoras story is genuinely unconfirmed, not a settled fact. It's a real, old, widely repeated tradition, but the historical record simply doesn't establish it with confidence. Fitting, for a course opening on the discipline that spends most of its time asking "how do you actually know that?"

The Major Branches

Philosophy is standardly organized into four core branches, each asking a genuinely different kind of question:

Metaphysics

What is there, and what is it really like? Reality's most general features — existence, objects, causation, space and time.

Epistemology

What can we know, and how do we know it? The nature, sources, and limits of knowledge itself.

Ethics

What ought we to do? Right and wrong conduct, and what makes an action or a life good.

Logic

What makes an argument good? The formal study of correct reasoning itself.

Several further, more specialized subfields build directly on these four: aesthetics (beauty and art, extending value theory the way ethics extends it to action), political philosophy (justice and the state, largely applied ethics at the level of a whole society), philosophy of mind (a genuinely specialized corner of metaphysics, focused specifically on consciousness and mental states), and philosophy of religion (arguments for and against religious claims, drawing on both metaphysics and epistemology at once). This course devotes a chapter to each.

Philosophical Method: Argument and Thought Experiment

Philosophy's own core tool is the argument — a set of premises offered in support of a conclusion, built to be evaluated on whether the premises are actually true and whether the conclusion genuinely follows from them (Chapter 2 covers this properly). Its second major tool is the thought experiment: a carefully constructed hypothetical scenario designed to isolate one specific intuition and test it directly, stripped of the noise of a real, messy situation.

The Trolley Problem

Philosophy's own most famous modern thought experiment began with Philippa Foot's real 1967 paper, built originally to examine the doctrine of double effect in the abortion debate — a pilot deciding whether to divert a crashing plane toward a more or less populated area, or a tram driver choosing which track to steer onto. Judith Jarvis Thomson's own 1976 article gave the scenario its now-famous name and developed it into the many variations (including the well-known "Fat Man" case) that fill philosophy classrooms today. The method's real value: when two scenarios with functionally identical outcomes produce genuinely different moral verdicts, that gap reveals something real about the actual structure of moral reasoning — something a bare statement of principle alone would never expose.

A Preview of What's Ahead The trolley problem is, in effect, a direct live test of the exact disagreement Course 2 already introduced: does only the aggregate outcome matter, as Bentham and Mill's utilitarianism (Course 2, Ch.6) would suggest, or does the type of action matter independently of outcome, as Kant's categorical imperative (Course 2, Ch.4) would insist? Chapters 5 and 6 of this course pick that live disagreement up directly.

How This Course Uses Its Own Cast

Rather than introducing an entirely new set of thinkers, this course draws repeatedly on the cast Courses 1 and 2 already built — organized here by the question each branch asks, not by when each thinker lived.

Chapter	Branch	Draws heavily on
Ch.2	Logic & Critical Thinking	Aristotle (C1.4), Frege & Russell (C2.7)
Ch.3	Epistemology	Descartes, Locke, Berkeley, Hume (C2.2-3), Kant (C2.4)
Ch.4	Metaphysics: Free Will, Personal Identity & Mind	Aristotle, Descartes, Hume (C2.3), Chalmers (C2.9)
Ch.5-6	Ethics	Aristotle (C1.4), Kant (C2.4), Bentham & Mill (C2.6)
Ch.7	Political Philosophy	Locke (C2.3), Mill (C2.6), Rawls (C2.9)
Ch.8	Philosophy of Religion	Aquinas (C1.10), Hume (C2.3)

	Courses 1 & 2	Course 3 (This Course)
Organized by	Chronology — one era at a time	Theme — one branch at a time
A single chapter might span	A century or two	Two and a half thousand years
Best for	Seeing how one idea led to the next	Seeing how a single question has been answered differently across all of history at once

Where This Goes Next — Chapter 2 covers logic properly: the structure of a good argument, validity and soundness, and the common fallacies that make a bad argument look convincing anyway — the toolkit every later chapter in this course will lean on directly.

Questions to Sit With

Reflection 1

Does organizing philosophy by branch (this course) or by chronology (Courses 1 and 2) change what you actually take away from it? Which structure do you expect to find more useful, and why?

Reflection 2

The trolley problem strips away real-world complexity to isolate one moral intuition at a time. Is that simplification a genuine strength of the method, or does it risk testing intuitions about a situation too artificial to tell us much about real moral life?

Reflection 3

Metaphysics, epistemology, ethics, and logic are presented here as the four core branches, with everything else built on top of them. Can you think of a genuine philosophical question that doesn't fit cleanly into any of the four?

Quick Reference — Chapter 1

Etymology — philosophia, "love of wisdom"; the Pythagoras coinage story is real but genuinely unconfirmed
Four core branches — metaphysics (what is there?), epistemology (what can we know?), ethics (what ought we to do?), logic (what makes an argument good?)
Extended subfields — aesthetics, political philosophy, philosophy of mind, philosophy of religion
Method — the argument (premises → conclusion) and the thought experiment
The trolley problem — real origin in Philippa Foot's 1967 paper, named by Judith Jarvis Thomson's 1976 article
This course organizes by branch, drawing repeatedly on the full cast already introduced in Courses 1 and 2