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Revision notes 'A Defense of Skepticism' - Peter Unger
? "[E]very human being knows, at best, hardly anything to be so."
? It's not just the concept of 'certainty' that is problematic, but also a host of other, similar terms such as 'flat'. o These are basic absolute terms. o When you use constructions of degree with them, you are really talking about how close something comes to being accurately described by them.
? However with relative terms this isn't the case.
? Certainty is an absolute concept, whereas confidence is a relative one.
? "[A]s a matter of logical necessity, if a surface is flat, then there never is any surface which is flatter than it is." o So we shouldn't believe there are physical objects with flat surfaces. Neither should we believe we can be certain of things.
? But does knowing require being certain?
o Yes. "[I]t is by being wrongly serious about this casual
[everyday] talk that philosophers...have come to think it rather easy to know things to be so."
? "[W]hatever analysis of knowledge is adequate, if any such there be, it must allow that the thesis of scepticism be at least fairly plausible." DeRose & Warfield
? Argument by sceptical hypothesis: o I don't know that not-H o If I don't know that not-H, then I don't know that O o So, I don't know that O [Uses the closure principle]
? Semantic Externalism: the contents of at least some of one's thoughts are not completely determined by "internal" facts about what is going on inside one's head, but are at least partially determined by such "external" facts as the nature of the items one has been in contact with.
? Putnam's BIV argument seems to rely on this? (So that BIVs' terms don't refer).
? Putnam assumes that BIVs have always been BIVs, but if one has been recently envatted then one can have experienced objects and therefore refer to them with language. So even on semantic externalism a BIV can be falsely thinking, "I am not a BIV".
? NB with internalism/externalism debate, very difficult to distinguish between internal and external factors anyway.
? "Perhaps the lesson of scepticism is that we don't know that we know the things in question, or that we can't show that we know them, or some other such thing."
Perhaps our whole concept of justification is based on how we use propositions in relation to each other and therefore cannot be applied to all propositions needing to be justified by something else that is not a member of that set. Epistemic closure principle: If you know P, and you know that P entails Q, then you also know that Q. 'Relevant alternatives' theory of knowledge: true belief + being in a position to rule out all the relevant alternatives to what one believes. (Dretske) o "You can know that P without knowing everything that you know that P entails, for P will entail the falsity of all the contraries or alternatives to P, but you need only know the falsity of the relevant alternatives to P in order to know that P."
? But then you need a criterion of relevance. Contextualism as a response to scepticism: Lewis says the sceptic exploits the "Rule of Attention" according to which those alternatives to which we're paying attention are relevant. They make relevant those alternatives that we typically (and properly) ignore. Unger admits that varying standards for knowledge govern our use of sentences of the form "S knows that P" but does not endorse contextualism. The varying standards are simply standards of whether it is 'appropriate' to say that S knows, but truth conditions are constant and obviously context-independent. o 'Invariantism'.
'Elusive Knowledge' - David Lewis
? "Maybe epistemology is the culprit. Maybe this extraordinary pastime robs us of our knowledge. Maybe we do know a lot in daily life; but maybe when we look hard at our knowledge, it goes away."
? "Maybe ascriptions of knowledge are subtly context-dependent, and maybe epistemology is a context that makes them go false."
? Lewis doesn't think justification is the mark of knowledge. o It's neither always necessary nor sufficient.
? "Subject S knows proposition P iff P holds in every possibility left uneliminated by S's evidence; equivalently, if S's evidence eliminates every possibility in which not-P."
? The uneliminated possibilities are those in which the subject's entire perceptual experience and memory are just as they actually are.
? Let E have propositional content P. Then E eliminates possibility W iff W is a possibility in which the subject's experience or memory has content different from P. o NOT that E eliminates W iff W is a possibility in which P is false.
? "[I]f I say that every uneliminated possibility is one in which P...I am doubtless ignoring some of all the uneliminated alternative possibilitites that there are. They are outside the domain, they are irrelevant to the truth of what was said."
Rules to tell us what we can and cannot ignore: o The Rule of Actuality: the possibility that actually obtains is never properly ignored; actuality is always a relevant alternative; nothing false may properly be presupposed. (NB by actuality we mean the subject's actuality). o The Rule of Belief: a possibility that the subject believes to obtain is not properly ignored, whether or not he is right to so believe. Neither is one that he ought to believe to obtain, whether or not he does so believe.
? NB this is rough because there are degrees of belief. Plus, don't use the converse to the Rule of Belief. o The Rule of Resemblance: suppose one possibility saliently resembles another. Then if one of them may not be ignored (in virtue of the other rules), neither may the other.
? But this causes problems. Because the possibility that the subject is being deceived by an evil demon resembles actuality in the respect that it is also uneliminated by the subject's evidence. And Lewis does not know how to reformulate this rule to avoid this result.
? "The Rule of Resemblance also is the rule that solves the Gettier problems: Other cases of justified true belief that are not knowledge." In the Ford case, "I do not know, because I have not eliminated the possibility that Nogot drives a Ford he does not own whereas Havit neither drives nor owns a car. This third possibility may not properly be ignored." (Because of all the rules). o The Rule of Reliability: we can ignore possibilities that don't take perception, memory or testimony for granted, within limits.
? This "may be defeated by the Rule of Actuality. Or it may be defeated by the Rules of Actuality and of Resemblance working together."
? "The general presupposition that vision is reliable consists...of a standing disposition to presuppose, concerning whatever particular case may be under consideration, that we have no failure in that case." o The Rules of Method: We are entitled to presuppose that a sample is representative, and that the best explanation of our evidence is the true explanation. o The Rule of Conservatism: Suppose that those around us normally do ignore certain possibilities, and it is common knowledge that they do (and expect each other to, etc.) Then these generally ignored possibilities may properly be ignored. This seems quite suspect...
o The Rule of Attention: when we say that a possibility is properly ignored, we mean exactly that; we do not mean that it could have been properly ignored; a possibility not ignored at all is ipso facto not properly ignored.
"What is and what is not being ignored is a feature of the particular conversational context." When we do epistemology, we are attending to possibilities that we wouldn't usually attend to. So in that context, they cannot be properly ignored. "Sometimes our conversational purposes are not altogether shared, and it is a matter of conflict whether attention to some far-fetched possibility would advance them or impede them." "[P]resuppositions alone are not a basis on which to claim knowledge." "Better knowledge is more stable knowledge: it stands more chance of surviving a shift of attention in which we begin to attend to some of the possibilities formerly ignored." o So does knowledge admit of degrees?
Ascriptions of knowledge "are a handy but humble approximation." "The premise 'I know that I have hands' was true in its everyday context, where the possibility of deceiving demons was properly ignored. The mention of that very possibility switched the context midway." "If we evaluate the conclusion for truth not with respect to the context in which it was uttered, but instead with respect to the different context in which the premise was uttered, then truth is preserved."????
'Skepticism' - Nozick
? S knows that p iff:
1. S believes p;
2. p is true;
3. If p were true, S would believe p;
4. If p were not true, S would not believe p
? In sceptical cases, "the p he believes is false, and he believes it even though it is false." Thus not all of Nozick's conditions for knowledge are satisfied anyway.
? R: Even if p were false, S still would believe p.
? But, R is stronger than the skeptic needs in order to show that 4 is false.
? "Perhaps the possibility the skeptic adduces is not enough to show that R is true, but it appears at least to establish the weaker T; since this T denies 4, the skeptic's possibility appears to show that 4 is false."
? "However, the truth of 4 is not incompatible with the existence of a possible situation where the person believes p though it is false."
? "[S]ubjunctive conditionals differ from entailments; the subjunctive 4 is not a statement of entailment"
? "Not every possible situation in which p is false is the situation that would hold if p were false...the subjective 4 speaks of the not-p
???????world that is closest to the actual world, or of those not-p worlds that are closest to the actual world." o "What happens in yet other more distant not-p worlds is not concern of the subjunctive 4." Call the sceptic's possibilities 'SK'. SK count against 4 only if they would or might obtain if p were false; only if one of these possibilities is in the not-p neighbourhood of the actual world. "According to our account of knowledge, S knows that the skeptic's situation SK doesn't hold if and only if 1) SK doesn't hold 2) S believes that SK doesn't hold 3) If SK were to hold, S would not believe that SK doesn't hold 4) If SK were not to hold, S would believe that it does not." Focus on the third condition. Sceptic chooses SK so that 3) doesn't hold > we do not know that SK doesn't hold. "The skeptic asserts we do not know his possibilities don't obtain, and he is right. Attempts to avoid scepticism by claiming we do know these things are bound to fail." "Let us say that a situation (or world) is doxically identical for S to the actual situation when if S were in that situation, he would have exactly the beliefs (doxa) he actually does have." "More generally, two situations are doxically identical for S if and only if he would have exactly the same beliefs in them." Nozick agrees with the sceptic that we do not know SK, but says that this doesn't stop one from knowing. The sceptic "intends...to work things backwards, arguing that since the person does not know that q, assuming...that he does know that p entails q, it follows that he does not know that p." "Knowledge is not closed under known logical implication." "That you were born in a certain city entails that you were born on earth. Yet contemplating what (actually) would be the situation if you were not born in that city is very different from contemplating what situation would hold if you weren't born on earth." "There is no reason to assume the (closest) not-p world and the (closest) not-q world are doxically identical for you, and no reason to assume, even though p entails q, that your beliefs in one of these worlds would be a (proper) subset of your beliefs in the other." "Because what is preserved under logical implication is truth, any condition that is preserved under known logical implication is most likely to speak only of what happens when p, and q, are true, without speaking at all of what happens when either one is false. Such a condition is incapable of providing "varies with"; so adding only such conditions to true belief cannot yield a adequate account of knowledge." "A belief's somehow varying with the truth of what is believed is not closed under known logical implication. Since knowledge that
p involves such variation, knowledge also is not closed under known logical implication." "The skeptic cannot easily deny that knowledge involves such variation, for his argument that we don't know that we're not floating in that tank, for example, uses the fact that knowledge does involve variation." But the other part of his argument does rely on the closure principle, and he thus can't be right in both parts. "Only by fixating on the skeptical possibilities SK can he maintain his skeptical virtues; otherwise, unsurprisingly, he is forced to confess to sins of credulity."
'Epistemic Operators' - Dretske
? (Sentential) operators: those that, when affixed to a sentence or statement, they operate on it to generate another sentence or statement. E.g. 'it is true that', 'it is a fact that', 'it is necessary that', 'it is possible that'.
? With these 4 prefixes, "if Q is a necessary consequence of P, then the statement we get by operating on Q with one of these four operators is a necessary consequence of the statement we get by operating on P with the same operator." o If P entails Q, then O(P) entails O(Q) for these operators. o These are (fully) penetrating operators.
? Not all sentential operators are like this! E.g. epistemic operators such as 'reason to believe that', 'know that'. o Also 'it is strange that', 'it is accidental that'. o The above are 'nonpenetrating'.
? All epistemic operators are semi-penetrating operators.
? "[O]ur epistemic operators will turn out not to be penetrating because, and perhaps only because, the agents in question are not fully cognizant of all the implications of what they know to be the case, can see to be the case, have a reason to believe is the case, and so on."
? Assume that when Q is a necessary consequence of P, every relevant agent knows that it is. o Wants to show that even under this restriction, the epistemic operators are only semi-penetrating.
? Almost all scepticism seems to trade on the idea that the epistemic worth of a proposition is hereditary under entailment: 'if S doesn't know whether or not Q is true, then for all she knows it might be false. If Q is false then P must also be false. So for all S knows, P may be false. Therefore S does not know that P is true.'
? "[T]he traditional sceptical arguments exploit precisely those consequences of a proposition to which the epistemic operators do not penetrate, precisely those consequences which distinguish the epistemic operators from the fully penetrating operators." o E.g. having reason to believe the church is empty does not entail having reason to believe that it is a church.
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