Lecture 9.2 Response to skepticism

Lecture Overview

  • Course: phil20490 Knowledge and Scepticism

  • Lecture Number: 9.2

  • Topic: Responses to Scepticism

Argument for External World Scepticism

  • Key Points:

      1. Evidence does not completely rule out the possibility that I am a brain-in-a-vat (BIV).

      1. Knowledge (p) is only gained if evidence completely rules out the possibility that p is false.

      1. Therefore, one does not know they are not a BIV.

      1. To know one has a body, one must know they are not a BIV.

      1. Hence, if one does not know they are not a BIV, they cannot know they have a body.

    • Conclusion: One does not know they have a body.

Sceptical Reasoning

  • Sceptic's Argument:

      1. You do not know you are not a BIV.

      1. If you do not know you are not a BIV, you do not know you have hands.

      1. Therefore, you do not know you have hands.

  • Counter Reasoning:

      1. I know you have hands.

      1. If I know you have hands, I know you are not a BIV.

      1. Thus, I know you are not a BIV.

  • Moore's Challenge: Which inference should we prefer?

The Contextualist Response

  • Definition:

    • Epistemic contextualism holds that key epistemic terms vary by context, affecting their meaning.

    • Examples: Terms like 'I', 'you', 'that', 'good', 'bad', etc. are context-sensitive.

  • Contextualism about Knowledge:

    • Contextualism asserts that 'knows' is context-sensitive and reflects language theory rather than knowledge definition.

Simplified Contextualism Model

  • Definition (S knows that p):

    1. S believes that p.

    2. p is true.

    3. S’s evidence rules out contextually relevant possibilities where p is false.

    • Condition (3) differs based on context but aligns with the Evidence Principle.

Questions Raised by Contextualism

  • Question 1: What defines our evidence?

    • Potentially includes perceptual experiences and memories.

    • Supports an internalist view of justification and knowledge.

  • Question 2: What does it mean for evidence to rule out relevant possibilities?

    • E.g., seeing a cat rules out the possibility there is no cat unless countered by hallucination or deception.

The Role of Context in Knowledge

  • Knowledge Contexts:

    • Some contexts permit knowing (e.g., belief and evidence rule out false possibilities), while others do not (considering deceptive scenarios).

  • Acknowledges that knowledge can fluctuate between contexts without contradicting itself.

Contextualism's Interaction with Scepticism

  • Contextualists argue scepticism arises from excessively demanding contexts, while less stringent contexts allow for knowledge.

  • Philosophers debate the balance between scepticism and the assertion of knowledge in adverse scenarios.

Contextualism: Benefits and Costs

  • Benefits:

    • Explains why scepticism seems compelling without altering behavior; people recognize scepticism in high-stakes contexts but revert to low-stakes contexts easily.

    • Illustrates dynamic knowledge understanding in conversations.

  • Costs:

    • Difficulty expressing the theory consistently due to conflicting knowledge standards.

    • Challenges in communicating shared knowledge across contexts.

Further Reading and Watching

  • Recommended articles and sources for deeper understanding.

    • Stanford Encyclopedia of Philosophy: Contextualism in Epistemology.

    • Hannon, M. ‘Scepticism and Contextualism’.

    • DeRose, K. ‘Solving the Sceptical Problem’.

The Sensitivity Response

  • Moore and the Sceptic's Agreement:

    • Holds to the Closure Principle (CP): Knowledge can be inferred from known premises.

  • Arguments:

    • Sceptic's Argument vs. Moore's Proof using CP:

        1. BIVs lack hands.

        1. If I have hands, I'm not a BIV.

        1. I have hands.

      • Conclusion from (2) and (3) leads to the assertion of knowledge.

Arguments For and Against Closure Principle

  • In Favor:

    • Intuitively seems logical to think knowledge extends to valid inferences.

  • Against:

    • Some propositions may be too difficult to know, despite logical inference.

Applications of Sensitivity and Closure Principle

  • Lottery Case:

    • Knowledge claimed based on logical recognition of unlikely events, but may not truly be known.

  • Philosophical Implications:

    • Challenges the connection between knowledge and deceived perceptions of reality (e.g. cleverly painted mules vs. zebras).

Nozick's Sensitivity Condition

  • Understanding the Condition:

    • A subject S knows that p if:

      1. S believes p.

      2. In closest possible scenarios where p is false, S does not believe p.

  • Implications:

    • Fails for false beliefs.

Application Examples: Gettier Cases and Scepticism

  • Gettier Cases:

    • Demonstrate sensitivity failure through situational similarities.

  • Impact on Scepticism:

    • Queries about sensitivity inform beliefs regarding BIV scenarios and physical traits like having hands.

Conclusion of Sensitivity Response

  • Evaluation of Claims:

    • Nozick's position conflicts with CP, recognizing limits of knowledge assertions.

    • Skepticism produces challenges for consistent relations between knowledge and reality.