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Gail Stine, "Skepticism, Relevant Alternatives, and Deductive Closure"

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Gail Stine, G. C. STINE SKEPTICISM, RELEVANT ALTERNATIVES, AND DEDUCTIVE CLOSURE (Received 2 February, 1975) Discussionsof skepticism,defined with varyingdegrees of precision,are of courseperennial in philosophy.Some recentdiscussions of the issue1 giveprominence to the notionof 'relevantalternatives', according to which a claimto knowthat p is properlymade in the contextof a limitednumber of competingalternatives to p; to be justifiedin claimingto knowp (or simplyto knowp) it is sufficientto be ableto ruleout alternativesrelevant to that context.This seemsto me to be a correctand hearteningdevelop- ment. Recent epistemologicaldiscussions have also broughtup a rela- tively new subject,which is the validityof the generalform of argument: (A) a knows that p a knows thatp entailsq .,. a knows that q I shall call this the principleof epistemicdeductive closure, or simply,in this paper, deductive closure.2 What is interesting about recent comments on this principleis that it is perceivedto have somethingto do with skepticism- in fact to leadto it - and henceis currentlyof verybad repute. And 'relevantalternatives' views of knowledgevis-'a-vis skepticism are supposedto show us the falsity of the principle. In this paper I propose to do three things. First, to give a qualified argumentfor deductiveclosure. Second, to give a qualifiedargument againstskepticism which will make use of the relevantalternatives idea. It will be similarto othersin leavingrather indeterminate the way in which the contextdetermines what is takento be a relevantalternative, although I shall distinguishdifferent sources of this indeterminatenessand draw some furtherconclusions. Third, I shall give an unqualifiedargument to the effect that the questionsof the validity of the principleof epistemic deductiveclosure and skepticismare completely irrelevant to one another, and that in fact properattention to the idea of relevantalternatives tends to confirmthe principle.This, of course,puts me in directconflict with the recenttrend I have mentioned. PhilosophicalStudies 29 (1976) 249-261. All Rights Reserved Copyright? 1976 by D. ReidelPublishing Company, Dordrecht-Holland This content downloaded from 128.122.149.154 on Wed, 11 Sep 2013 01:11:58 AM All use subject to JSTOR Terms and Conditions 250 G. C. STINE 1. EPISTEMICDEDUCTIVE CLOSURE I am in principle suspicious of all principles of epistemic logic on the general grounds that while the logic of a knower who is in some way simplifiedand idealizedmay be usefulfor limitedpurposes, what we are ultimately interested in are actual knowers who can be pretty obtuse and idiosyncratic,yet still lay claim to knowledge.For this, among other reasons, I have elsewhere been concerned with epistemic logic which eschews possible worlds semantics imposing strong constraints on knowers.3Certainly, I would rejectthe patternwhich goes: (B) a knows that p p entails q .. a knows that q However,the patternwhich I have labeled epistemicdeductive closure does seem to representa certainbare minimum.One looks naturallyfor counter-instances involving failure of belief where p and q are very com- plicated,but any such case I can imagineturns out to be apparentonly becauseit invariablyraises doubts about the truth of the secondpremise which are as strongas the doubts about the truth of the conclusion.The principleseems to be on a par with epistemicconjunction, to wit: (C) a knows p a knows q .,.aknowspandq There have, of course, been problemsin reconcilingthis principlewith commitmentsto rationalbelief in terms of degreesof confirmationand knowledgein terms of rationalbelief,4 but one feels stronglyinclined to the view that the adjustmentmust be made in the area of these commit- ments and not in the principleof conjunction. In additionto failureof belief, one may look for counter-examplesto the principle of epistemic deductiveclosure in the area of failure of evidence or warrant.One's initial reaction to this idea is that if one's evidenceis not sufficientfor knowingq, it is not sufficientfor knowingp, either, wherep is known to entail q. I shall be returningto this subject later, for some philosophers to whom I have referred deny this point This content downloaded from 128.122.149.154 on Wed, 11 Sep 2013 01:11:58 AM All use subject to JSTOR Terms and Conditions SKEPTICISM AND RELEVANT ALTERNATIVES 251 which seems, initially,fairly obviousand I shall arguethat their reasons are mistaken. Actually,if instead of (A) we adopt the strongerepistemic deductive closureprinciple: (D) a knowsp a knows q a knows(p *q entailsr) .,. a knows r (A) and (C) may be seen as instancesof a common principle,provided we allow 'a knows (p q entails p q)' as an uncontroversial instance of the third premise.5(D) is, ultimately,what we need, anywayto capture the idea of knowingthe knownlogical consequencesof what one knows, for (A) covers only the known consequencesof the things one knows taken individually,not the known consequencesof one's whole body of knowledge.And although(D) is strongerthan (A), the argumentsfor (A) workjust as stronglyfor (D), and, so far as I can see, thereare no argu- ments that anyone might seriouslyoffer against(D) which do not also applyto (A). However,for the sake of simplicityand conformityto other discussionsin the literature,I shall continueto discussdeductive closure in the form of (A). In summary,I am not absolutelyconvinced of the validityof the prin- ciple of epistemicdeductive closure, as I am not absolutelyconvinced of the validityof the principleof epistemicconjunction, but in neithercase can I think of an objection,and in both cases, apparentproblems they lead to (skepticism,inconsistency) are eitherapparent only or are better handledby givingup other less obvious principles. 2. SKEPTICISM In Belief, Truth and Knowledge, D. M. Armstrongargues: It is not a conclusiveobjection to a thermometerthat it is only reliablein a certainsort of environment.In the same way, reliabilityof belief, but only within a certainsort of environment,would seem to be sufficientfor the believerto earnthe accoladeof knowl- edge if that sort of environmentis part of his boundary-conditions.6 For example,I know that the stripedanimal I see in the zoo is a zebra.7 I know this despitethe fact that I have no particularevidence that it is This content downloaded from 128.122.149.154 on Wed, 11 Sep 2013 01:11:58 AM All use subject to JSTOR Terms and Conditions 252 G. C. STINE not a mule paintedto look like a zebra (I have not looked for a paint can, tried paint removeron the animal, etc.). In this context - under normalcircumstances, in zoos of integrity,etc. - that an animalon display has been deliberatelydisguised to fool trustingzoo-goers is just not a relevanthypothesis, one that I need trouble myself about rejecting.If the skeptictries to persuademe to his position by stressingmy lack of evidenceagainst such an hypothesis,my properresponse is to turna deaf ear. He has ensnaredme by impropermeans and is more than halfway to (illegitimately)winning his point if he gets me to agree that I must arguewith him, go look for furtherevidence, etc. This view, which I call the relevantalternative view, seemsto me fun- damentallycorrect. It does leave a lot of thingsunsaid. What are normal circumstances?What makes an alternativerelevant in one context and not in another?However, in ordinarylife, we do exhibit ratherstrong agreementabout what is relevantand what is not. But there are grey areas.Alvin Goldmanmakes this point nicelywith the followingexample which he attributesto Carl Ginet: if on the basis of visual appearances obtainedunder optimumconditions while drivingthrough the country- side Henry identifiesan object as a barn, normallywe say that Henry knowsthat it is a barn.Let us suppose,however, that unknownto Henry, the region is full of expertlymade papier-machefacsimiles of barns.In this case, we would not say Henryknows that the objectis a barn,unless he has evidenceagainst it being a papier-machefacsimile, which is now a relevantalternative. So much is clear, but what if no such facsimiles exist in Henry'ssurroundings, although they do in Sweden?What if they do not now exist in Sweden,but they once did? Are either of these cir- cumstancessufficient to makethe hypothesisrelevant? Probably not, but the situationis not so clear. Another area of obscurityresides not in the natureof the case but in the formulationof the view in question. Goldman seems to hold what I regardas the correctversion of it, which is that: (1) an alternativeis relevantonly if thereis some reasonto think that it is true. But there is also the view that: (2) an alternativeis relevantonly if thereis some reasonto think it couldbe true. This content downloaded from 128.122.149.154 on Wed, 11 Sep 2013 01:11:58 AM All use subject to JSTOR Terms and Conditions SKEPTICISM AND RELEVANT ALTERNATIVES 253 Clearly,the force of the 'could'cannot be merelogical possibility,or the relevantalternative view would lose its distinguishingfeature. However, if the 'could'is readin some strongerway, we could still have a versionof the relevant alternativeview. Dretske's 'ConclusiveReasons' 8 paper, espousing a view accordingto which if one knows, then given one's evidence,one couldnot be wrong(he reads'could' as 'physicallypossible') suggeststhat we should consideran hypothesisa live one unless it could not be true,given one's evidence. Hence any alternativewould be relevant, in the sense of blockingknowledge, if one has not the evidenceto rule it out, so long as it is physicallypossible, given one's evidence.Also, the passagein 'EpistemicOperators' where Dretske says: "A relevantalter- native is an alternativethat might have been realized in the existing circumstancesif the actualstate of affairshad not materialized",9is more akin to (2) than (1), althoughso taking it dependson the force of his 'might'.This, I think, is the wrong way to take the relevantalternative view. First of all, howeverunclear it may be as to when there is some reasonto think an alternativeis true, it is muchmore unclearas to when thereis reasonto think it could be true. Certainly,if thereis a difference between(1) and (2), (2) is weaker,allows more to count as a relativealter- native.
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