Epistemology is the branch of [[index|philosophy]] concerned with the nature, sources, and limits of knowledge. The word derives from the Greek episteme (knowledge) and logos (study). It asks: what is knowledge, how do we get it, and how much can we trust it?
- What is knowledge, and how does it differ from mere belief or opinion?
- How do we acquire knowledge — through reason, experience, or both?
- What are the limits of what we can know?
- Is [[Consciousness|conscious]] experience a reliable guide to reality?
Since [[Plato]]'s Theaetetus, knowledge has been defined as justified true belief (JTB):
- You believe p
- p is true
- Your belief in p is justified
This was challenged by Edmund Gettier (1963), who produced counterexamples where JTB seems insufficient. Gettier cases have driven much of contemporary epistemology.
Knowledge is primarily derived from reason and innate ideas, independent of sense experience. Key figures:
- [[Descartes]] — used radical doubt to find the one certain truth: cogito ergo sum
- [[Kant]] — argued some knowledge (a priori) is possible prior to experience
- [[Plato]] — true knowledge is of eternal [[The Forms|Forms]], not changing appearances
Knowledge is derived from sensory experience. Key figures:
- [[Locke]] — the mind begins as a blank slate (tabula rasa); all ideas come from experience
- [[Hume]] — pushed empiricism to skeptical conclusions about causation and the self
- [[Aristotle]] — grounded knowledge in observation of the natural world
[[Kant]] argued that experience provides the content of knowledge, while reason provides its structure (space, time, causality). Neither alone is sufficient.
We cannot be certain of anything, or at least should suspend judgment:
- [[Descartes]]' method of radical doubt: could an evil demon be deceiving me?
- [[Hume]]'s problem of induction: past experience gives no logical guarantee about the future
- [[Wittgenstein]] shifted the question: when and how is doubt even intelligible?
| Term | Meaning |
|---|---|
| A priori | Knowledge prior to experience (e.g., mathematics, logic) |
| A posteriori | Knowledge dependent on experience (e.g., empirical facts) |
| Analytic | True by meaning alone ("all bachelors are unmarried") |
| Synthetic | True by how the world is ("the cat is on the mat") |
| Foundationalism | Knowledge rests on basic, self-evident beliefs |
| Coherentism | Beliefs are justified by their coherence with each other |
| Internalism | Justification depends only on the agent's own mental states |
| Externalism | Justification can depend on factors external to the agent |
- [[Metaphysics]] — what we can know about the nature of reality
- [[Logic]] — the formal tools for evaluating inference and argument
- [[Consciousness]] — raises deep questions about the reliability of perception
- [[Free Will]] — connects to whether rational agents can be genuinely autonomous
- [[Phenomenology]] — investigates the structures of experience from the first-person view
- [[Ethics]] — metaethics asks whether moral knowledge is possible
- [[Plato]] — knowledge of the [[The Forms|Forms]] vs. mere opinion about appearances
- [[Aristotle]] — knowledge grounded in empirical observation and [[Logic]]
- [[Descartes]] — the Meditations as a systematic attempt to ground certain knowledge
- [[Locke]] — Essay Concerning Human Understanding: the mind as blank slate
- [[Hume]] — Enquiry Concerning Human Understanding: skepticism about causation and induction
- [[Kant]] — Critique of Pure Reason: the conditions for the possibility of knowledge
- [[Wittgenstein]] — Philosophical Investigations: knowledge as embedded in social practice