Some Reflections on Contemporary Attitudes to Scepticism

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  • Slide 1
  • Some Reflections on Contemporary Attitudes to Scepticism
  • Slide 2
  • Lecture Plan 1.Closure Principles and Transmission 2.Contextualism 3.Externalism 4.Theories of Perception
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  • 1. Closure Knowledge is NOT closed under entailment: If K(P) and (P Q), it does not follow that K(Q) Otherwise mathematics would be easy! This is not valid: 1.K(I am in Shanghai) 2.If I am in Shanghai, then I am not being deceived by and evil demon 3.So, K(I am not being deceived)
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  • Known Entailment Is knowledge closed under known entailment? If K(P) and K( P Q ), then K(Q) This looks like it must be true Are there exceptions? Crispin Wright and Martin Davies have both suggested that there may be special cases where transmission of warrant fails warranted = permissible to claim to know
  • Slide 5
  • Failure of closure Suppose I see some zebras in the zoo. I am warranted in asserting the zoo has zebras. I know that if the zoo has zebras then the animals I saw were not cleverly disguised horses. I am not warranted in asserting the zoo has not replaced all its zebras with cleverly disguised horses.
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  • Explanation K(P), K(P Q), ~K(Q) why? Because the permissibility of claiming K(P) on basis of what I see Presupposes that Q is true. So I cannot transmit warrant from P to Q, because warrant for P depends upon Q being warranted.
  • Slide 7
  • Application to evil demon 1.K(there is a chair in front of me) This is warranted by my perceptual experience 2.K(if there is a chair in front of me, then I am not being deceived by the evil demon) 3.Therefore, K(I am not being deceived ) The warrant for 1. presupposes I am not being deceived Sceptical argument (not-3 therefore not-1) fails
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  • Problems Only applies to Cartesian scepticism Cogency relies on defeasibility of warrant: I have warrant for P and P Q and but not for Q But if I do know P and P Q, then Q must be true So either: one of those warrants holds despite not knowing, or: Q is true If ~K(P) then sceptic wins, so we would have to show that despite having warrant, ~K(P Q)
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  • 2. Contextualism Ascriber relative standards: Is the floor flat? You: Yes Movie camera crew: No Do I know that the flight will land on time? You: Yes [delays are rare and not much depends on it] Passenger with transfer: No [I havent checked there are no delays]
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  • Contextualism: It is the context of the ascriber, not the subject, which determines relevant standards for knowledge N.B. Warrant is self-ascription of knowledge, so as well as interpersonal differences of standards, there can be intrapersonal variations over time. Contrast: Subject Sensitive Invariantism: The practical interests of the subject determine standards for knowledge. This doesnt help against sceptic.
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  • Application to scepticism 1.K(there is a chair in front of me) 2.K(if there is a chair in front of me, then I am not being deceived by the evil demon) 3.K(I am not being deceived ) In ordinary contexts, 1 and 2 are true and 3 follows. If the ascriber is in a context where scepticism is relevant, then 3 is false, but since 2 is still true, 1 is false. (David Lewis, Elusive Knowledge)
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  • Commitments 1.The contextualist must give a semantics in which truth values can change with context of assertion. I.e. know does not have a constant semantic value 2.The contextualist must give a theory of contexts which shows that scepticism is not relevant in ordinary contexts. Especially for someone who has been exposed to sceptical arguments
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  • Problems 1.The semantics makes this look like we are just changing the topic From certainty to moral certainty But that is not what the Cartesian sceptic cares about 2.This needs to show more than Humes point that we do in fact ignore scepticism in ordinary life Must show we are justified to do so That looks question-begging
  • Slide 14
  • 3. Externalism Two versions: 1.Modest strategy: Hilary Putnam, Reason, Truth and History (1981) 2.Bold strategy: Gregory McCulloch, The Life of the Mind (2003)
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  • Modest Strategy 1.Meaning is not an intrinsic property Obvious with words Less obvious with images Even less obvious with thoughts 2.The relations which partially determine the meaning (content) of thoughts are causal 3.The evil demon / brain-in-a-vat (BIV) sceptical scenario involves changing world-to-mind causal relations
  • Slide 16
  • 4.These changes will change the content of the deceived subjects thoughts 5.If I am not BIV, then my thought that I am not BIV will be true 6.If I am BIV, then my thought that I am not BIV will be true. 7.So whether or not the sceptical hypothesis is true, my thought that I am not BIV is true.
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  • Why modest? Modest because allows that sceptical hypothesis describes a possible situation Bold strategy will deny this Also only applies to certain sceptical hypotheses E.g. does not rule out that I was BIV yesterday But does rule out that I know nothing about the external world Fodor: We are all BIV anyway Question is whether we are BIV in touch with reality
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  • Problems 1.At best, we know that whatever the BIV means when she thinks that I am not BIV, it will not be the same as what we think. But that doesnt make it true. 2.From the sceptics perspective, Putnam has only established the meta-linguistic claim: the sentence I am not a BIV is true. 3.Since we dont know whether BIV or not, and that changes the content of our thoughts, we dont know what we are thinking.
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  • Bold Strategy The bold externalist strategy is: We can only have any thoughts at all if we are connected to the world in the right way The right way is the way we appear to be connected to the world in the Manifest Image So all forms of Cartesian scepticism and Scientific Realism are ruled out But not Pyrrhonism
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  • Problem Most philosophers argue: 1.Conceivability entails possibility 2.The sceptical scenarios are conceivable 3.So, the sceptical scenarios are possible 4.Phenomenological externalism entails sceptical scenarios are not possible 5.So, phenomenological externalism is false.
  • Slide 21
  • My own view I agree with McCullochs conclusion but for different reasons (coming later) But the argument against is strong The only effective way out is to accept there are impossible worlds Conceivability entails true at some world But maybe only at impossible worlds. E.g. impossible time travel stories
  • Slide 22
  • 4. Perception All sceptical arguments have a common assumption: our perceptual experiences could be false The world could be other than how we perceive it to be It was central to Berkeleys rejection of scepticism to deny this Can we deny it without accepting immaterialism?
  • Slide 23
  • Aside: Davidsons view Donald Davidson, Epistemology Externalized (1991) That EACH perception might be false does not entail that they might ALL be false E.g. counterfeit money In order to understand our experiences as perceptions as of an external world, At least some must be true E.g. crazy robot with random inputs not responding to environment at all. But which ones??
  • Slide 24
  • Disjunctivism (Snowdon 1980, McDowell 1994): What we call perceptual experiences come in two distinct kinds with no common factor. 1.Veridical (true) perceptual experiences are not the kind of thing that could occur without the world being as it seems to be 2.Illusions and hallucinations are the kind of thing which can, and often do, occur when the world is not as it seems to be So the relation between a veridical experience and the world is not contingent
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  • How does this help? Cartesian scepticism required that the connection between my mental states and the world was contingent. According to the disjunctivist, the state of veridically perceiving is not one I could have in the sceptical scenario So being in such a state rules out scepticism and gives me knowledge
  • Slide 26
  • How does this work? This looks like the asymmetric structure of Descartes response to the dreaming argument, but applied to the evil demon While dreaming is cognitively disabling The evil demon is perceptually disabling: He prevents me getting in to the perceptual states I am in when not deceived Thus when not deceived I have an epistemic resource (perception) not available in the sceptical scenario
  • Slide 27
  • Problems 1.Veridical and non-veridical experiences, though of different kinds, are reflectively indistinguishable So while this gives me knowledge, it does not let me know that I know (KK Principle false) Is that sceptical? Perhaps not 2.Vulnerable to Pyrrhonist opposing accounts arguments But one set of appearances is not mere appearance
  • Slide 28
  • A more radical approach What if we denied that that there are illusions or hallucinations or dreams? What if the only perceptual experiences are the veridical ones? Then no forms of perceptual scepticism would be possible This is the perceptual version of McCullochs externalism: In the sceptical scenario I simply would not be having conscious perceptual experiences
  • Slide 29
  • To make such an iconoclastic view


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