What is epistemology?
Epistemology (from Greek episteme, knowledge) is the study of knowledge. It asks three big questions:
- What is knowledge? How is it different from belief or opinion?
- How do we get it? From reason, the senses, memory, other people?
- How sure can we be? Can we ever be certain?
Types of knowing: knowing that (facts: water boils at 100 °C at sea level), knowing how (skills: riding a cycle) and knowing by acquaintance (knowing a person or a place).
Knowledge as justified true belief
An old idea, going back to Plato, says you know something when three conditions hold:
- Belief: you accept it.
- Truth: it is actually so.
- Justification: you have good reasons or evidence.
A lucky guess is not knowledge because it has no justification. Plato also separated opinion (changeable, based on appearances) from knowledge (stable, based on reasons). Aristotle stressed knowing the causes of things through observation and logic.
The Gettier problem
In 1963 Edmund Gettier showed cases where a belief is true and justified but true only by luck. Example: you look at a stopped clock that happens to show the right time. You have a reason (clocks usually work), it is true, but you do not really know the time. So many thinkers add a fourth condition, such as "no luck" or "reliable method".
Reason and experience
Rationalism (Descartes, Leibniz): the most certain knowledge comes from reason, like mathematics and logic. Descartes doubted everything he could and found one thing he could not doubt: "I think, therefore I am."
Empiricism (Locke, Hume): knowledge comes from experience through the senses. Locke said the mind starts like a blank slate.
Kant joined them: experience gives the content, but the mind gives the structure (space, time, cause). Many other traditions discuss sources of knowledge too; for example, classical Indian philosophy lists pramanas such as perception (pratyaksha), inference (anumana) and reliable testimony (shabda).
Ways of knowing include sense perception, reason, language, emotion, imagination, faith, intuition and memory. Each helps and each can mislead.
What is truth?
- Correspondence theory: a statement is true if it matches the facts. "Snow is white" is true if snow really is white.
- Coherence theory: a statement is true if it fits well with a whole system of other beliefs we accept.
- Pragmatic theory: a belief is true if it works and is useful when we act on it.
Science mostly uses correspondence (test against the world) plus coherence (fit with other theories). Truth is different from belief: people once believed the Sun went round the Earth, but that did not make it true.
Doubt, scepticism and the context of knowledge
Scepticism questions whether we can know anything for certain. Senses mislead (a stick in water looks bent), memory fades, and dreams can feel real. Healthy doubt makes us test claims, look for evidence and check sources.
Context: what counts as good evidence depends on the area. In mathematics we need proof; in science, repeatable experiments; in history, reliable sources; in law, evidence beyond reasonable doubt. Religious and moral language raise their own questions: some treat such claims as matters of faith and meaning rather than things tested in a lab. Knowledge is also shared: we depend on experts, books and communities, so trust must be earned.
Key formulas and definitions
- Knowledge (classic) = Belief + Truth + Justification (JTB)
- Rationalism: knowledge from reason; Empiricism: knowledge from experience
- Truth theories: correspondence, coherence, pragmatic
- Knowing that / knowing how / knowing by acquaintance
- A priori (known before experience) vs a posteriori (known from experience)
Worked examples
1. Riya guesses the answer to a quiz question and gets it right. Did she know it?
No. Her belief was true, but she had no justification. A lucky guess is not knowledge.
2. Classify: (a) all triangles have three sides, (b) water boils at 100 °C at sea level.
(a) A priori, known by reason from the meaning of the words. (b) A posteriori, known from experience and experiment.
3. A man looks at a clock that stopped exactly 12 hours ago; it shows the correct time. Does he know the time?
This is a Gettier case: his belief is true and justified, but it is true by luck. Most philosophers say he does not know.
4. A rumour says a bridge is closed. How can you turn it into knowledge?
Check reliable sources: official traffic updates, the city website, or see it yourself. If the claim is true and your reasons are good, you now know.
Common mistakes
- Thinking belief and knowledge are the same. You can believe something false.
- Thinking that if many people believe it, it must be true.
- Saying empiricists reject all reasoning, or rationalists reject all experience. Most use both.
- Treating scepticism as "nothing matters". It means asking for good reasons.