Nozick, Knowledge and Skepticism (from Philosophical Explanations) Flashcards
What is the skeptic’s argument about knowledge?
The skeptic argues that we cannot know ordinary facts (e.g., “I am reading a book”) because we cannot rule out radical possibilities like:
- Being deceived by an evil demon.
- Dreaming or hallucinating.
- Being a brain in a vat with artificial experiences.
These scenarios are logically possible and indistinguishable from reality, undermining claims to knowledge.
What are Nozick’s four conditions for knowledge?
To know that p, the following must hold:
Truth: p is true.
Belief: S believes that p
Sensitivity to Falsehood: If p were false, S wouldn’t believe p (not-p
p → not- (S believes p)).
Sensitivity to Truth: If p were true,
S would believe p (p → S believes p).
This ensures the belief “tracks” the truth.
How does Nozick’s theory handle the brain-in-a-vat scenario?
A brain in a vat believes it’s reading a book, but this fails condition 4: If it were reading a book (which it isn’t), it wouldn’t believe it (since the vat would simulate otherwise).
Thus, the brain doesn’t track the truth, so it lacks knowledge, even if its belief is true.
How does Nozick use subjunctive conditionals and possible worlds?
Subjunctive conditions (e.g., “If p were false, S wouldn’t believe p”) assess belief in nearby possible worlds where p’s truth value changes.
“Closeness” of worlds is key: Skeptical worlds (e.g., brain-in-a-vat) are distant, so they don’t disrupt knowledge in nearby worlds (e.g., ordinary perception).
Why does Nozick reject the closure principle?
Closure Principle: If
S knows p, and p entails q, then S knows q.
Nozick argues knowledge isn’t closed because condition 3 (sensitivity) can fail for q even if it holds for p.
Example: I know I’m in Jerusalem (p), which entails I’m not a brain in a vat (q). But I don’t track q (if q were false, I’d still believe q), so I don’t know q.
How does Nozick reconcile skepticism with everyday knowledge?
We don’t know skeptical hypotheses are false (e.g., “I’m not a brain in a vat”) because we fail to track them.
But we do know ordinary facts (e.g., “I’m reading”) because we track them in nearby worlds.
Key Insight: Knowledge is non-closed, so skepticism about radical scenarios doesn’t imply skepticism about everything.
What are “doxically identical worlds,” and why do they matter?
Definition: Worlds where S has the same beliefs as in the actual world, but these beliefs may be false (e.g., brain-in-a-vat worlds).
Importance: Shows knowledge is mediated—our beliefs can match reality or a perfect deception. Skepticism exploits this gap, but Nozick argues we still track truth in ordinary cases.
How does Nozick explain Hume’s “skepticism vanishes outside the study”?
Hume notes skepticism feels compelling in theory but fades in practice (e.g., playing backgammon).
Nozick explains: In daily life, we track ordinary facts (fulfilling conditions 1–4), making skepticism psychologically unsustainable when focusing on these truths.
What advantages does Nozick’s theory have?
- Handles Gettier Cases: Explains why justified true belief isn’t enough (e.g., Ford example fails condition 3).
- Explains Skepticism’s Appeal: Shows why we can’t know skeptical hypotheses are false.
- Preserves Everyday Knowledge: Allows knowledge of ordinary facts while conceding skepticism’s limits.
What are potential weaknesses of Nozick’s account?
- Non-Closure Controversy: Rejecting closure clashes with intuitive reasoning (e.g., knowing
p but not its obvious consequences). - Vagueness of “Closeness”: No clear metric for “nearby” possible worlds.
- Overemphasis on Subjunctives: Conditions 3–4 may be too stringent, ruling out plausible knowledge (e.g., beliefs formed via reliable but non-subjunctive processes).
