Introduction to philosophy lecture 8 epistemology 1
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Introduction to Philosophy Lecture 8 Epistemology #1. By David Kelsey. Epistemology. Epistemology: the theory of knowledge. analyzes concepts such as belief, truth, knowledge, justification and opinion. Some epistemological questions include: What is knowledge?

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Introduction to Philosophy Lecture 8 Epistemology #1

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Introduction to PhilosophyLecture 8Epistemology #1

By David Kelsey


  • Epistemology:

    • the theory of knowledge.

    • analyzes concepts such as belief, truth, knowledge, justification and opinion.

  • Some epistemological questions include:

    • What is knowledge?

    • Which of my beliefs do I know?

    • How do I know them?

Defining Knowledge

  • Knowledge: is often contrasted with mere opinion or mere belief.

  • Beliefs without knowledge: But knowledge is more than just belief for I can have beliefs about all sorts of things without knowing them.

  • True Belief: so for a belief to count as knowledge the belief must be true.

Knowledge and justification

  • Knowledge: is also more than mere true belief.

    • Example:

  • Justified beliefs: to count as knowledge, my true beliefs must be justified.

    • A held belief is justified: just when one has a reason to hold that belief.

Knowledge as JTB

  • Knowledge as JTB: we might try to define knowledge as justified true belief then.

  • Thus, S knows that p if and only if:

    • S believes that p and

    • P is true and

    • S’s belief that p is justified

  • Individually Necessary: Each of these three conditions is necessary for S to know that p.

  • Jointly sufficient: together the 3 conditions are jointly sufficient for S to know that p.

Gettier & Knowledge

  • Edmund Gettier

    • Born in 1927

    • Philosophy professor at University of Massachusetts Amherst since 1967

    • In his article Is Justified True Belief Knowledge? Gettier argues that something’s being justified true belief is not a sufficient condition for it’s being knowledge.

      • Thus, he argues that one can have a justified true belief and yet not have knowledge.

      • Gettier provides two counterexamples to prove his point.

Smith, the job &10 coins

  • Smith, the job & 10 coins: Smith believes that

    • Jones is the man who will get the job and Jones has 10 coins in his pocket.

    • Smith is justified in this belief:

      • The company president and counting…

  • Smith infers: so Smith infers that The man who will get the job has ten coins in his pocket.

    • He is justified given closure and because he validly inferred it…

  • Smith gets the job: unbeknownst to Smith, not only will he get the job but he also has 10 coins in his pocket.

    • So not only is Smith justified in his belief that the man who will get the job has ten coins in his pocket, but this belief is true.

  • But Smith doesn’t know it…

The Ford &Barcelona

  • Now Smith gains evidence for the proposition: That Jones owns a Ford (‘F’)

    • Smith remembers and Jones drives up in a Ford…

  • Brown is where: Smith has another friend named Brown of whose whereabouts Smith is totally ignorant.

    • Smith then believes: Either Jones owns a Ford or Brown is in Barcelona. (‘H’)

  • A is Justified: Smith is justified in holding H because:

    • Smith is justified in holding F

    • H is entailed by F

    • Smith makes the proper inference from F to H.

  • Brown in Barcelona: now imagine that both Jones doesn’t own a Ford and that Brown really does live in Barcelona.

    • JTB without knowledge…

Replies to Gettier

  • Denying the assumptions: The first way we might reply to Gettier is to deny some of the assumptions he makes. He assumes that:

    • It is possible for a person to be justified in believing a proposition that is false

    • Closure: for any proposition P, if S is justified in believing P &

      • P entails Q &

      • S deduces Q from P &

      • S accepts Q as a result of this deduction, then

      • S is justified in believing Q.

      • Snowing so Freezing…

  • The first assumption is uncontroversial really

  • But maybe we can deny the second assumption…

Denying Closure

  • Denying closure: We could deny Closure by holding an Externalist theory of justification.

    • Externalism is so called because Externalists are not interested in what’s going on internally, I.e. in your head, when you know something.

    • Inference doesn’t guarantee justification: the Externalist can deny that the mental state of inferring can justify one’s beliefs.


  • Here’s an example of an Externalist theory of justification:

    • S is justified in believing that P iff P is formed by a reliable belief forming process.

  • So Justification doesn’t come from inference but reliability…

More replies to Gettier

  • Accepting the counterexamples: We might also reply to Gettier by accepting his counterexamples to the traditional definition of knowledge.

    • Finding another analysis: In this case we are then out to find a more adequate analysis of KNOWLEDGE.

    • Infallible evidence:S knows that p iff S believes P, P is true and P is justified for S by infallible or absolutely certain evidence.

Other possible definitions of knowledge

No false steps: Knowledge is justified true belief where the reasoning your belief is based on doesn’t proceed through any false steps.

  • A false step: is just some belief you hold in your pattern of reasoning which is false.

Last thoughts on defining knowledge

  • Knowledge is a graded concept:

    • Conceptual analysis is impossible: This reply is more a reply to being able to define concepts at all.

      • Some people think that finding adequate definitions for our concepts is near impossible.

      • Some people go so far as to say conceptual analysis is impossible in and of itself.

    • Graded: One reply to this kind of worry is to say that concepts have a graded nature.

      • Knowledge is of a scale…

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