Read it, map it, or hear it
The same ideas, three ways. Start wherever suits you; everything is cross-linked.
ReadThe guideSixteen chapters, from the Gettier problem to Bayes' theorem, with worked examples and self-checks.
ExploreThe concept map135 ideas as a living map you can pan and expand, in English and Persian, each with a full entry.
ListenThe audio editionEvery chapter narrated, 14½ hours in all, with section markers and a quiz after each chapter.What this site does
Mastering Epistemology is a free, open-source web app for learning epistemology and critical thinking.
Read, explore and listen
A free guide to knowledge, evidence and critical thinking: sixteen chapters with self-checks, a glossary, a map of the concepts in English and Persian, and every chapter narrated, to play here, offline, or in a podcast app.
Study tools
Highlights and notes, reading progress, spaced review questions, and an optional AI study companion that answers questions about the page you are reading, using your own Claude or ChatGPT API key. Everything works without an account and is kept in your browser.
Optional Google sign-in
Sign in with Google to keep your progress, notes, review deck and settings in sync across your devices. The site uses your name, email and picture only to show who is signed in, and saves your study data in a private app folder in your own Google Drive; it cannot see your other files. There is no server of ours, no ads and no tracking.
Sixteen chapters, each with a masterpiece
Every chapter opens with a painting or photograph that captures its question, from Raphael's School of Athens to the Earthrise photograph.
Foundations
CHAPTER 1What Is Epistemology?
The central questions; three kinds of knowing; belief, credence, and acceptance; the a priori, analytic, and necessary; epistemic versus practical reasons; the map of the field
CHAPTER 2A History of the Theory of Knowledge
From the Presocratics, Socrates, Plato, and Aristotle through Indian, Islamic, and Chinese traditions, Descartes, Locke, Hume, Reid, and Kant, to pragmatism, Popper, Wittgenstein, Quine, and Gettier
CHAPTER 3Logic and the Anatomy of Arguments
Deduction, induction, and abduction; validity and soundness; conditionals and necessary/sufficient conditions; valid forms and formal fallacies; hidden premises; charity; argument mapping; the Toulmin model
CHAPTER 4Language, Concepts, and Definitions
Sense and reference; kinds of definition; ambiguity and vagueness; verbal disputes; loaded language and framing; contested concepts; the is–ought gap; thought experiments; reflective equilibrium
The Core of Epistemology
CHAPTER 5What Is Knowledge?
Justified true belief; the Gettier problem; reliabilism, sensitivity, safety, virtue, and knowledge-first theories; epistemic luck; the value of knowledge; understanding and wisdom
CHAPTER 6Justification: The Structure of Good Reasons
Defeaters; the regress problem; foundationalism, coherentism, infinitism, and their hybrids; internalism versus externalism; evidentialism; the problem of the criterion; fallibilism
CHAPTER 7The Sources of Knowledge
Perception, memory, introspection, reason, and testimony: how each works and how each fails; knowledge by presence; when to trust intuition
CHAPTER 8Skepticism and Its Answers
Pyrrhonian and Cartesian skepticism; the brain in a vat; the closure argument; Moore, contextualism, hinge epistemology, and other responses; healthy versus corrosive skepticism
Evidence, Science, and Truth
CHAPTER 9Induction, Probability, and Bayesian Reasoning
Hume's problem; grue and the ravens; probability; Bayes' theorem with worked examples; base rates, the conjunction fallacy, Monty Hall, regression to the mean, Simpson's paradox; calibration; p-values and risk
CHAPTER 10Science, Evidence, and Explanation
Falsifiability; Duhem–Quine; Kuhn and Lakatos; inference to the best explanation; realism; causation, correlation, and randomized trials; values in science; consensus; the replication crisis; spotting pseudoscience
CHAPTER 11Truth, Relativism, and Objectivity
Theories of truth; the liar paradox; relativism and its critics; social construction; objectivity and perspective; post-truth and bullshit
Knowledge in Society and in the Mind
CHAPTER 12Social Epistemology: Knowing Together
Trust and expertise; choosing between experts; peer disagreement; epistemic injustice; standpoint theory; echo chambers; cascades and crowds; misinformation, propaganda, and conspiracy theories; institutions; AI
CHAPTER 13Intellectual Virtue and the Ethics of Belief
Clifford versus James; intellectual virtues and vices; humility and open-mindedness; pragmatic and moral encroachment; faith, reason, and religious epistemology
CHAPTER 14The Psychology of Reasoning: How Minds Actually Work
Dual-process theories; heuristics and biases; confirmation and myside bias; motivated reasoning; overconfidence; identity-protective cognition; the argumentative theory; what debiasing works; superforecasting
Practice
CHAPTER 15A Field Guide to Fallacies
More than forty fallacies and rhetorical tactics, each with examples, its legitimate cousin, and how to respond; practice exercises
CHAPTER 16The Critical Thinker's Toolkit: Analyzing Discussions and Framing Arguments
A seven-step method for analyzing any discussion; stasis theory; finding the crux; framing your own arguments; burden of proof; razors; the ethics of discussion; five worked case studies; checklists
Appendices
“The duty of the man who investigates the writings of scientists, if learning the truth is his goal, is to make himself an enemy of all that he reads.”