The Definition of Knowledge

Tripartite definition of knowledge

Knowledge is Justified True Belief (JTB).

Who proposed the tripartite definition of knowledge?

Plato, in Theaetetus

What does 'tripartite' mean?

It has three parts: Justified, True, Belief.

What does JTB aim to do?

Provide the necessary and sufficient conditions for knowledge.

What does 'necessary condition' mean?

Something that must be present for the thing to count (e.g. being male is necessary to be a bachelor).

What does 'sufficient condition' mean?

Something that, if present, is enough to make the thing count (e.g. being an unmarried man is sufficient to be a bachelor).

What does 'individually necessary' mean (in JTB)?

Each condition (justification, truth, belief) must be present for knowledge.

What does 'jointly sufficient' mean (in JTB)?

Together, all three conditions should be enough to count as knowledge.

Why is truth necessary for knowledge?

You can't know something false - e.g. 'I know the moon is made of cheese' is false, so not knowledge.

Why is belief necessary for knowledge?

You can't know something you don't believe - 'I know today is Monday but don't believe it' makes no sense.

Why is justification necessary for knowledge?

Luck isn't enough - guessing Pluto has 5 moons is true but unjustified, so not knowledge.

What did Gettier challenge?

The sufficiency of the tripartite definition (JTB).

What does Gettier argue?

Some justified true beliefs are true only by luck and should not count as knowledge.

Gettier Case 1 Summary

Smith believes 'the man who will get the job has 10 coins.' It's justified and true—but true only by coincidence (he himself gets the job).

What does Gettier Case 1 show?

JTB can be true by coincidence, not genuine knowledge.

Gettier Case 2 Summary

Smith believes 'Either Jones owns a Ford or Brown is in Barcelona.' Jones doesn't, but Brown happens to be in Barcelona - true by luck.

What does Gettier Case 2 show?

Even justified true beliefs can be true for the wrong reason (disjunction condition), so JTB isn't sufficient for knowledge.

Definition: Lemma

A step or assumption used in reasoning to reach a conclusion.

Is justification necessary?

Possibly not - animals and children seem to know things without being able to justify them.

Is truth necessary?

Some philosophers like Zagzebski remove 'truth' as an explicit condition, replacing it with intellectual virtue.

Is belief necessary?

You might 'know' something subconsciously even if you don't consciously believe it (e.g., forgotten facts recalled correctly).

What is the 'no false lemmas' definition?

Knowledge is JTB plus 'not inferred from anything false.'

Formal version of JTB + N

P is true; you believe P; your belief is justified; and your belief is not inferred from any false lemma.

How does ‘No False Lemmas’ solve Gettier Case 1?

Smith's belief was based on the false lemma 'Jones will get the job,' so it isn't knowledge.

Why is 'no false lemmas' better than JTB?

It fixes Gettier cases by excluding beliefs that rely on false premises.

Problem with JTB + N (Fake Barn County)

Henry's belief 'there's a barn' is justified, true, not inferred from falsehood—but true by luck, so still not knowledge.

What is reliabilism?

Knowledge is a true belief formed by a reliable cognitive process.

Examples of reliable methods

Good eyesight, memory, sense perception, introspection

Examples of unreliable methods

Guessing, wishful thinking, biased sources.

Strength of reliabilism

Explains how animals and young children can have knowledge through reliable sensory processes.

Problem with reliabilism (Fake Barn County)

Henry's vision is reliable, but his true belief is still lucky—so reliabilism wrongly says he knows.

What is virtue epistemology?

Defines knowledge as a true belief that is formed through the exercise of intellectual virtues.

T+B+Virtue

Response to Gettier Case

Intellectual virtues

Traits like rationality, careful reasoning, and truth-seeking that contribute to the acquisition of knowledge.

Analogy to moral virtue

Just as moral virtues lead to good actions, intellectual virtues lead to true beliefs.

Zagzebski's critique of 'true belief + X'

Any definition of 'true belief + some condition' can be defeated by Gettier-style luck cases.

Zagzebski's formula for Gettier cases

Take a case where a belief is false due to bad luck, then make it true due to good luck - it still fits 'true belief + X' but isn't knowledge.

Zagzebski's definition of knowledge

James knows that P if: 1. James believes P, 2. James's belief arises from an act of intellectual virtue.

Link between truth and virtue

Virtuous acts aim at and achieve truth; true beliefs must arise because of intellectual virtue, not luck.

Sosa's 'AAA' model

A model in Virtue Epistemology consisting of Accuracy (belief is true), Adroitness (belief formed through intellectual skill), and Aptness (belief is true because of that skill).

Apt belief

A belief that is true due to the believer's intellectual virtue, not coincidence.

Fake Barn County

A scenario where Henry's belief isn't apt - true only by luck, not through intellectual skill.

Infallibilism

A belief counts as knowledge only if it is true and justified in such a way that it cannot possibly be wrong.

Infallibilism's rejection of Gettier cases

Smith's belief isn't certain; it could be mistaken, so it's not knowledge.

Main problem with infallibilism

It sets the bar too high - almost nothing can be known with absolute certainty.

Example showing infallibilism's strictness

Even 'water boils at 100°C' could be doubted (thermometer error, brain-in-vat scenario, etc.).

Summary of infallibilism's issue

Gettier shows JTB is too lenient; infallibilism goes too far the other way - it makes knowledge nearly impossible.

Tripartite Definition (JTB) - Strengths

Simple, intuitive, long-standing; captures three core aspects of knowing.

Tripartite Definition (JTB) - Weaknesses

Fails due to Gettier cases; allows 'lucky' true beliefs to count as knowledge.

JTB + No False Lemmas - Strengths

Solves Gettier's original examples by ruling out beliefs based on false premises.

JTB + No False Lemmas - Weaknesses

Still fails under Fake Barn County (true belief by luck, not inference).

Reliabilism - Strengths

Explains how animals and children can have knowledge; focuses on real-world reliability.

Reliabilism - Weaknesses

Luck (Fake Barn County) still passes; 'reliable' can be vague or context-dependent.

Virtue Epistemology - Strengths

Links truth and justification through intellectual virtue; handles luck via 'aptness.'

Virtue Epistemology - Weaknesses

Excludes children/animals; defining intellectual virtue can be subjective.

Infallibilism - Strengths

Guarantees certainty; rules out all Gettier cases.

Infallibilism - Weaknesses

Unrealistic; makes knowledge almost impossible since nearly everything can be doubted.

Overall Evaluation of the Debate

Philosophers continually refine the definition of knowledge to avoid luck-based Gettier cases, but each new condition faces its own counterexamples.

Three types of knowledge

Acquaintance knowledge, ability knowledge, and propositional knowledge.

Acquaintance knowledge

Knowledge of something through direct experience or familiarity, e.g. 'I know Paris well' or 'I know my friend.'

Ability knowledge

Knowledge how to do something, e.g. 'I know how to play the piano' or 'I know how to swim.'

Propositional knowledge

Knowledge that something is the case, e.g. 'I know that Paris is the capital of France.'

Difference between types of knowledge

Acquaintance = familiarity, Ability = skill, Propositional = factual or truth-based knowledge.

Focus of epistemology

Propositional knowledge.

A priori knowledge

knowledge gained/justified independently of, or prior to, experience

A posteriori knowledge

knowledge containing propositions that cannot be determined independently from experience, and rely on sensory observations and empirical data

Standard form for JTB

P is knowledge if:

- P is true

- S believes in P

- S is justified in believing in P

Standard form for Reliabilism

P is knowledge if:

- P is true

- S believes in P

- S's belief that P was formed by a reliable cognitive process