Definitions of Knowledge — Summary Notes Summary & Study Notes

🧭 Overview

These notes focus on definitions of propositional knowledge (knowledge that P). Philosophers have proposed several accounts: Justified True Belief (JTB) and variants, JTB + No False Lemmas, Reliabilism, Virtue Epistemology, and Infallibilism. A central task is to give necessary and sufficient conditions for knowledge.

🧠 Kinds of Knowledge

There are three broad types of knowledge. This summary concerns the third type.

• Ability (know‑how): e.g. “I know how to ride a bike.”
• Acquaintance (know‑of): e.g. “I know Fred.”
• Propositional (know‑that): e.g. “I know that London is the capital of England.”

📚 Justified True Belief (Tripartite) — The Classic Account

The tripartite account (from Plato’s Theaetetus) says knowledge = belief + truth + justification. Each condition seems necessary: belief is required for knowledge, truth is required for knowledge, and justification rules out lucky true beliefs. The hope was that these three together would be sufficient.

⚠️ Gettier Problems — Counterexamples to JTB

Edmund Gettier produced cases showing that a person can have a justified true belief without having knowledge, because the truth arises from luck.

• Gettier Case 1 (Smith/Jones): Smith’s justified belief about “the man who will get the job has 10 coins” is true by coincidence (Smith, not Jones, gets the job and he also has 10 coins). The belief is justified and true but intuitively not knowledge.
• Gettier Case 2 (Disjunction): From a justified (but false) belief that Jones owns a Ford, Smith infers “Either Jones owns a Ford or Brown is in Barcelona.” By disjunction introduction the disjunction is justified; it turns out true because Brown is in Barcelona. Again, justified true belief fails to be knowledge. These cases show JTB is not sufficient.

🧩 Responses: Modify the Third Condition

Philosophers typically try to preserve truth and belief and refine the third condition so it rules out Gettier luck.

🚫 JTB + No False Lemmas (NFL)

This adds the requirement that the belief was not inferred from any false premises (no false lemmas). The NFL fix handles many Gettier cases where a false intermediate claim explains the justified belief (e.g. Smith’s belief inferred from the false lemma “Jones will get the job”). Problem: Fake Barn County. Henry looks at many fake barns and, by luck, sees the one real barn. His belief “there’s a barn” is true, justified, and not inferred from a false lemma, yet intuition says this is not knowledge because of the deceptive environment.

⚙️ Reliabilism

Reliabilism says S knows that P iff P is true and S’s belief that P was produced by a reliable cognitive process (one that tends to produce true beliefs). This explains how animals and young children can have knowledge: reliable perceptual processes can produce knowledge even without articulate justification. Advantage: accommodates children and animals. Problem: the fake barn case can also plague reliabilism: Henry’s visual process is reliable in normal contexts, but the local environment makes his true belief seem like luck; reliabilism may incorrectly count it as knowledge.

🌱 Virtue Epistemology

Virtue theories link knowledge to the exercise of intellectual virtues (traits like carefulness, intellectual skill, conscientious inquiry).

• Zagzebski’s critique: any definition framed as “true belief + X” is vulnerable to a Gettier‑style construction. She offers a formulation: start with a belief that meets X but is false due to bad luck, then tweak it so the belief is true by luck; the definition still classifies the second as knowledge. To solve this, Zagzebski emphasizes that knowledge must arise from an act of intellectual virtue, where the agent both intends truth and succeeds through virtuous cognitive activity. She treats truth as linked to virtuous success rather than a separate add‑on.

• Sosa’s account: distinguishes accuracy (belief is true), adroitness (skillful cognitive performance), and aptness (the belief is true because of the skill, not luck). Knowledge requires aptness, which supplies a direct link between the agent’s cognitive virtue and the truth, blocking Gettier luck.

Virtue approaches can avoid Gettier cases by insisting the truth must be because of the agent’s intellectual virtue. Objection: this may struggle to include very young children or animals as knowers if they lack the required intellectual virtues.

🔒 Infallibilism

Infallibilism demands that justification be strong enough to make the belief certain—immune to doubt—so that true, justified belief amounts to certainty. This blocks Gettier cases because those cases allow room for doubt. Problem: Infallibilism is often too demanding. Most ordinary beliefs (e.g. “water boils at $100^\circ C$”) can be doubted in extreme scenarios, so infallibilism risks denying that we know almost anything.

🔎 Zagzebski’s General Challenge

Zagzebski supplies a general formula generating Gettier‑style counterexamples against any theory that treats knowledge as “true belief + third condition” without adequately tying the truth to the third condition. The core insight: you must link truth to the epistemic condition (make the true result arise because of the epistemic good), not merely conjoin two independent properties.

✅ Summary and Comparative Notes

• The classic JTB account is intuitive but fails because of Gettier cases (luck undermines sufficiency).
• No False Lemmas repairs some Gettier cases but fails in environmental cases like fake barn county.
• Reliabilism handles animals and children by focusing on reliable processes but can be vulnerable to situation‑specific luck.
• Virtue epistemology (Zagzebski, Sosa) emphasizes that knowledge must arise from intellectual virtue and that truth must be linked to virtuous cognitive success (aptness), which blocks Gettier luck.
• Infallibilism avoids Gettier problems by requiring certainty but is implausibly strict.

Key takeaway: contemporary debates focus on how to connect truth to the epistemic condition (justification, reliability, or virtue) so that true belief is not merely accidental. Effective accounts must exclude lucky true beliefs while allowing ordinary knowledge (including that of animals and children) where appropriate.