Skepticism (Stanford Encyclopedia of Philosophy) Cite this entry Search the SEP • Advanced Search • Tools • RSS FeedTable of Contents• What's New• Archives• Projected ContentsEditorial Information• About the SEP• Editorial Board• How to Cite the SEP• Special CharactersSupport the SEPContact the SEP ©Metaphysics Research Lab,CSLI,Stanford University  Open access to the SEP is made possible by a world-wide funding initiative. Please Read How You Can Help Keep the Encyclopedia FreeSkepticismFirst published Sat Dec 8, 2001; substantive revision Wed Aug 31, 2005Much of epistemology has arisen either in defense of or inopposition to various forms of skepticism. Indeed, one could classifyvarious theories of knowledge by their responses to skepticism. Forexample, rationalists could be viewed as skeptical about thepossibility of empirical knowledge while not being skeptical withregard to a priori knowledge and empiricists could be seen as skepticalabout the possibility of a priori knowledge but not so with regard toempirical knowledge. In addition, many traditional problems, forexample the problem of other minds or the problem of our knowledge ofGod's existence, can be seen as restricted forms of skepticismwhich hold that we cannot have knowledge of any propositions in someparticular domain thought to be within our ken. This essay will focuson the general forms of skepticism which question ourknowledge in many, if not all, domains in which we ordinarily thinkknowledge is possible. Since this essay is not primarily devoted to adiscussion of the history of philosophical skepticism, the generalforms of skepticism to be discussed are those which contemporaryphilosophers still find the most interesting.1. Philosophical Skepticism vs. Ordinary Incredulity2. Two Basic Forms of Philosophical Skepticism3. Academic Skepticism4. The Argument for Academic Skepticism Employing the Closure Principle5. The Cartesian-style Argument for Academic Skepticism Employing the Eliminate All Doubts Principle6. Contextualism7. Pyrrhonism8. The Mode to Respond to the Foundationalist9. The Mode to Respond to the Coherentist10. The Mode to Respond to the Infinitist11. The Overall Effect of the ModesBibliographyOther Internet ResourcesRelated Entries1. Philosophical Skepticism vs. Ordinary IncredulityEven before examining the various general forms of skepticism, it iscrucial that we distinguish between philosophical skepticism andordinary incredulity because doing so will help to explain whyphilosophical skepticism is so intriguing. Consider an ordinary case inwhich we think someone fails to have knowledge. Suppose Anne claimsthat she knows that the bird she is looking at is a robin and that Ibelieve that if Anne were to look carefully, she would see that itscoloration is not quite that of a robin. Its breast is too orange.Further, I believe that it flies somewhat differently than robins do.This bird seems to flitter more than a typical robin.Thus, there are two grounds for doubting that Anne knows that thisis a robin:The color of this bird isn't typical of robins;The flight pattern of this bird is not typical of robins.Now, what makes this a case of ordinary doubt is that there are, inprinciple, two ways of removing the basis for doubt: Anne could show that the alleged grounds for doubt are false;orAnne could show that the grounds for doubt, though true, can be neutralized.[1]Taking alternative (i), Anne could show that there are many robinswith the coloration of the bird in question by citing the AudubonField Guide for Birds in which many of the pictured robins havevery orange breasts. In other words, Anne could show that (a) isfalse.But in order to remove grounds for doubt, it is not necessary thatAnne show that the alleged grounds are false. Consider ground (b). Itcould be granted that the bird in question flies in a way that is notat all typical of robins. But suppose that on closer inspection we seethat some of its tail feathers have been damaged in a way that couldaccount for the unusual flight pattern. Because the bird has difficultygliding and flying in a straight line, it flaps its wings much morerapidly than is typical of robins. Thus, although we can grant that (b)is true, we would have explained away, or neutralized, the grounds fordoubt.The point here is that in this case, and in all ordinarycases of incredulity, the grounds for the doubt can, in principle, beremoved. As Wittgenstein would say, doubt occurs within the context ofthings undoubted. If something is doubted, something else must be heldfast because doubt presupposes that there are means of removing the doubt.[2] We doubt that the bird is a robin because,at least in part, we think we know how robins typically fly and whattheir typical coloration is. That is, we think our general picture ofthe world is right — or right enough — so that it doesprovide us with both the grounds for doubt and the means forpotentially removing the doubt. Thus, ordinary incredulity, say aboutsome feature of the world, occurs against a background of sequesteredbeliefs about the world. We are not doubting that we have any knowledgeof the world. Far from it, we are presupposing that we do know somethings about the world. To quote Wittgenstein, "A doubt without an endis not even a doubt" (Wittgenstein 1969, ¶ 625).In contrast, philosophical skepticism attempts to render doubtfulevery member of a class of propositions that we think fallswithin our ken. One member of the class is not pitted against another.The grounds for either withholding assent to the claim that we can havesuch knowledge or denying that we can have such knowledge are such thatthere is no possible way to either answer them or neutralize them byappealing to another member of the class. Thus, philosophic doubt orphilosophical skepticism, as opposed to ordinary incredulity, does not,in principle, come to an end. Or so the philosophic skeptic willclaim!To clarify the distinction between ordinary incredulity andphilosophical doubt, let us consider two recent movies: "The TrumanShow" and "The Matrix." In the former, a character is placed, withouthis knowledge, in a contrived environment so that his "life" can bebroadcast on television. But he begins to wonder whether the worldsurrounding him is, in fact, what it appears to be. Some events seem tohappen too regularly and many other things are just not quite as theyshould be. Eventually, Truman obtains convincing evidence that all hisworld is a stage and all the men and women are merely players. Thecrucial point is that even had he not developed any doubts, there is,in principle, a way to resolve them had they arisen. Such doubts,though quite general, are examples of ordinary incredulity.Contrast this with the deception practiced in The Matrix. Wheneverything is running as programmed by the machines, there is nopossible way for the "people" in the matrix to determine that the worldas experienced is only a "dream world" and not the real world (theworld of causes and effects). The only "reality" that it is possible toinvestigate is a computer generated one. (See Irwin 2002, 2005 forcollections of articles on The Matrix.)The Truman Story is a depiction of a case of ordinary incredulitybecause there is some evidence available for determining what's reallythe case; whereas The Matrix depicts a situation similar to thatimagined by the philosophic skeptic in which it is not possible toobtain evidence for determining that things are not as they seem (atleast when the virtual reality is perfectly created). Put another way,the philosophic skeptic challenges our ordinary assumption that thereis evidence available that can help us to discriminate between the realworld and some counterfeit world that appears in all ways to beidentical to the real world. Ordinary incredulity arises within thecontext of other propositions of a similar sort taken to be known, andit can be removed by discovering the truth of some further propositionof the relevant type. On the other hand, philosophical skepticism abouta proposition of a certain type derives from considerations that aresuch that they cannot be removed by appealing to additionalpropositions of that type — or so the skeptic claims.These movies illustrate one other fundamental feature of thephilosophical arguments for skepticism, namely, that the debate betweenthe skeptics and their opponents takes place within the evidentialistaccount of knowledge which holds that knowledge is at least true,sufficiently justified belief. The debate is over whether the groundsare such that they can make a belief sufficiently justified so that aresponsible epistemic agent is entitled to assent to the proposition.[3] The basic issue at stake is whether thejustification condition can be fulfilled. A corollary of this is thatstrictly reliabilist or externalist responses to philosophic skepticismconstitute a change of subject. A belief could be reliably produced,i.e., its causal pedigree could be such that anything having thatcausal etiology is sufficiently likely to be true, but the reasonsavailable for it could fail to satisfy the standards agreed upon byboth the skeptics and their opponents.2. Two Basic Forms of Philosophical SkepticismConsider some proposition, p. There are just three possiblepropositional attitudes one can have with regard to p's truthwhen considering whether p is true. One can either assent top, or assent to ~p or withhold assenting both top and to ~p. Of course, there are other attitudes onecould have toward p. One could just be uninterested thatp or be excited or depressed that p. But thoseattitudes are either ones we have when we are not consideringwhether p is true or they are attitudes that result from ourbelieving, denying or withholding p. For example, I might behappy or sorry that p is true when I come to believe that itis. I just spoke of "assent" and I mean to be using it to depict thepro-attitude, whatever it is, toward a proposition that is required forknowing that proposition. Philosophers have differed about what thatattitude is. Some take it to be something akin to being certain thatp or guaranteeing that p (Malcolm 1963, 58-72).Others have taken it not to be a form of belief at all because, forexample, one can know that p without believing it as in casesin which I might in fact remember that Queen Victoria died in 1901 butnot believe that I remember it and hence might be said not to believeit (Radford 1966). For the purposes of this essay we need not attemptto pin down precisely the nature of the pro-attitude toward pthat is necessary for knowing that p. It is sufficient for ourpurposes to stipulate that assent is the pro-attitude toward prequired to know that p.Let us use "EI-type" propositions to refer to epistemicallyinteresting types of propositions. Such types of propositionscontain tokens some of which are generally thought to be known givenwhat we ordinarily take knowledge to be. Thus, it would not beepistemically interesting if we did not know exactly what the rainfallwill be on March 3 ten years from now. That kind of thing (a finegrained distant future state) is not generally thought to be knowngiven what we ordinarily take knowledge to be. But it would beepistemically interesting if we cannot know anything about the future,or anything about the contents of someone else's mind, or anythingabout the past, or anything at all about the "external world." We thinkwe know many propositions about those types of things.Now, consider the (meta) proposition concerning the scope of ourknowledge, namely: We can have knowledge of EI-typepropositions. Given that there are just three stances we can havetoward any proposition when considering whether to assent to it, wecan:Assent that we can have knowledge of EI-type propositions.Assent that we cannot have knowledge of EI-type propositions.Withhold assent to both that we can and that we cannot haveknowledge of EI-type propositions.Let us call someone with the attitude depicted in (i) an "Epistemist."[4] Such a person assents to the claim that wecan have knowledge of EI-type propositions.The attitude portrayed in (ii) has gone under many names. I willfollow the terminology suggested by Sextus Empiricus. He used the term"Academics" to refer to the leaders of the Academy (founded by Plato)during the 3rd to 1st century B.C. According to Sextus, they assentedto the claim that we cannot have knowledge of what I have calledEI-type propositions — although it is far from clear that thiswas an accurate description of their views. (See the entry on ancient skepticism.) Perhaps theprime example was Carneades (214-129 B.C.). Other philosophers willrefer to this view as "Cartesian skepticism" because of the skepticalarguments investigated by Descartes and his critics in the mid-17thcentury. And still others will refer to it as "switched worldskepticism" or "possible world skepticism" because the arguments for ittypically involve imagining oneself to be in some possible world thatis both vastly different from the actual world and at the same timeabsolutely indistinguishable (at least by us) from the actual world.What underlies this form of skepticism is assent to the propositionthat we cannot know EI-type propositions because our evidence isinadequate.Those assenting neither to the proposition that knowledge of EI-typepropositions is possible nor to the proposition that such knowledge isnot possible can be called "Pyrrhonian Skeptics" after Pyrrho who livedbetween ca 365 - ca 275 B.C. The primary source of PyrrhonianSkepticism is the writing of Sextus Empiricus who lived at the end ofthe second century AD. The Pyrrhonians withheld assent to everynon-evident proposition. That is, they withheld assent to allpropositions about which genuine dispute was possible, and they tookthat class of propositions to include the (meta) proposition that wecan have knowledge of EI-type propositions. Indeed, they sometimesclassified the Epistemists and the Academic Skeptics together asdogmatists because the Epistemists assented to the proposition that wecan have knowledge, while the Academic Skeptics assented to the denialof that claim.[5]Another difference between Academic and Pyrrhonian Skepticism isclosely related to the charge by the latter that the former is really adisguised type of dogmatism. The Academic Skeptic thinks that her viewcan be shown to be the correct one by an argument (or by arguments).The Pyrrhonian would point out that the Academic Skeptic maintainsconfidence in the ability of reason to settle matters — at leastwith regard to the extent of our knowledge of propositions in theEI-class. One way of understanding the so-called problem of the"Cartesian circle" illustrates the Pyrrhonian point: Descartes isrelying throughout the Meditations on his power of reasoningto remove the skeptical doubts that he raises, but to do so means thathe has exempted the faculty of reasoning from the doubts that he raisedin the "First Meditation" about the epistemic reliability of ourfaculties. A Cartesian reply could be as simple as paraphrasing Luther:Here I stand, as a philosopher with confidence in reason, and as such Ican do no other.[6] Regardless of the adequacy of that kind ofresponse, the point here is that the Pyrrhonians did not think thatthey had a convincing argument whose conclusion was that withholdingassent to non-evident propositions was the appropriate epistemicattitude to have.I think it is fair to say that Academic Skepticism is usually whatis meant when most contemporary philosophers write about skepticism.Thus, it is that form of skepticism to which we will now turn and it isthat form that will be the primary focus of this essay, although I willdiscuss some aspects of Pyrrhonism later.3. Academic SkepticismA way to motivate Academic Skepticism and to clearly distinguish itfrom ordinary incredulity is to trace the way in which Descartesexpanded the realm of what was doubtful (and hence not worthy ofassent) in the "First Meditation."[7] Descartes begins bynoting that the senses have deceived him on some occasions and, in thevoice of his skeptical interlocutor, he conjectures that it is neverprudent to trust what occasionally misleads. So, we don't have"certain" knowledge of the external world based upon the testimony ofour senses. However, in the voice of the non-skeptical interlocutor, hereplies that even though the senses have misled him, he can neutralizethat purported basis for doubt by pointing out that we are able todetermine when our senses are not trustworthy. Thus, this is a case ofordinary incredulity because he appeals to some knowledge of the worldgained through our senses to neutralize this basis for doubt. Forexample, in looking at a straight stick in water, even though itappears bent, we know not to accept the testimony of our senses at facevalue. We can neutralize the potentially knowledge-robbing propositionthat my senses have deceived me on some occasions by adding toit another proposition to which we assent, namely, I can distinguishbetween the occasions when my senses are trustworthy and those whenthey are not. Some propositions in the EI-type (propositions about theexternal world) can be used to rebuff the grounds for ordinaryincredulity. Thus, no basis for (philosophical) Academic Skepticism hasbeen located. Descartes next considers dreaming. What if he were dreaming at thatvery moment? Would he still have some knowledge of the external world?Yes; because in dreams and in waking life there are some common generalfeatures. So, if he were dreaming, he would not know in particular whatis going on about him at that moment, but that does not imply that hefails to have any knowledge at that moment. For example, he still couldknow that there are hands. More importantly, even more simple thingsabout nature "in general" are not thereby made doubtful. We have notfound any reason for doubting that there are material objects or thatthey have a spatial location, or are in motion or at rest, or can existfor a long or short period of time. Again, no basis for AcademicSkepticism has been established.But then Descartes thinks of a grounds for doubt for which he sayshe "certainly has no reply." He puts it this way:… In whatever way [it is supposed] that I havearrived at the state of being that I have reached — whether [itis attributed] to fate or to accident, or [made] out that it is by acontinual succession of antecedents, or by some other method —since to err and deceive oneself is a defect, it is clear that thegreater will be the probability of my being so imperfect as to deceivemyself ever, as is the Author of my being to whom [is assigned] myorigin the less powerful. (Meditations, 147)In other words, at this point in the Meditations, since helacks an argument for the claim that whatever is causally responsiblefor his "state of being" is capable of making his being such that toerr would not be natural for it, assenting to propositions arrived atby his "state of being" is not legitimate. Thus, Descartes believesthat he has located a basis for doubting all of his supposed formerknowledge of the external world that cannot be repulsed by locatinganother such proposition to which he is entitled. He has found aproposition that, if true, would (by itself) defeat the justificationhe has for his assenting to propositions about the external world andwhich is such that (1) he does not (at least at this point in theMeditations) have a way to reject it and such that (2) he hasno way to neutralize its effect. Thus, a basis for philosophicalskepticism has been found because an entire class of EI-typepropositions — propositions that his "nature" has led him toassent to — is now thrown into doubt because he cannot use onemember of the class to reject or neutralize the basis for doubtinganother member of the class. Descartes apparently thinks that something is worthy of assent onlyif it is immune to genuine doubt. It appears that he thinks thatsomething, d, is a grounds for genuine doubt of p forS iff:d added to S's beliefs makes assent to pno longer adequately justified;S is not justified in denying d;[8]S has no way to neutralize d.[9]The final step is to say that some proposition is not worthy of assentif there are genuine grounds for doubting it. Indeed, Descartes grantsthat even after d is located, p might still be morereasonable to believe than to deny (Meditations, 148). Thepoint is that the pro-attitude should not rise to the level requiredfor knowledge because there is a genuine ground for doubt. Thus, acrucial feature of the Cartesian-style argument for Academic Skepticismis that it employs a very stringent requirement on the type of evidencerequired for knowledge. It must make a proposition immune to genuinedoubt. To make that clear, let us state the epistemic principle, which wecan call the "Eliminate All Doubt Principle," that apparently informsthe Cartesian-style argument:Eliminate All Doubt Principle[EAD]: For all propositions x and d, if dsatisfies condition 1. in the definition of genuine doubt thatx, then if assenting to x is adequately justified forS, then S is adequately justified in eliminatingd (either by denying or neutralizing it).In more contemporary terminology, the ground for doubt proposed byDescartes can be put like this: U: My epistemic equipment isuntrustworthy.The Cartesian-style argument for Academic Skepticism can nowbe put like this: If I know that p, then there are no genuine grounds fordoubting that p.U is a genuine ground for doubting thatp.Therefore, I do not know that p.The Cartesian-style argument does not readily lend itself to theobjection that by employing it the skeptic is contradicting herself onthe grounds that the argument purportedly shows that she fails to knowbecause her epistemic equipment is untrustworthy while at the same timeshe is employing the very equipment that, were the argument sound,would be unreliable. The reason is that she is neither asserting thather equipment is untrustworthy nor claiming that there is an argumentwhich shows that her equipment is untrustworthy. She is merely claimingthat U is a genuine ground for doubt. Thus she neitheris holding contradictory beliefs nor is her practice somehowincompatible with her beliefs. The Cartesian-style argument for Academic Skepticism should becontrasted with what many contemporary philosophers take to be thecanonical argument for Academic Skepticism which employs the ClosurePrinciple (CP).[10] Letting "h" stand for an EI-typeproposition, for example, G. E. Moore's famous "here's a hand" andletting "sk" stand for "I am in a switched-world in whichthere are no hands, but it appears just as though there were hands," wecan state the canonical CP-style argument for AcademicSkepticism as follows:CP1. If I am justified in believing that h, then Iam justified in believing that ~sk. CP2. I am not justified in believing that ~sk.Therefore, I am not justified in believing that h.This argument appeals to a form of the Closure Principle in Premise 1.Letting "Jsx" stand for "S is justified in havingsome pro-attitude, J, regarding x," that principlecan be stated as: Closure Principle [CP]: For all propositions x and y, if x entailsy, and Jsx, then Jsy.(In the CP-style argument: x = h and y =~sk.) A crucial feature of CP is that it does not depend upon employing astringent notion of justification. Suppose that (positive)justification comes in degrees, where the lowest degree is somethinglike mere plausibility and the highest degree is absolute certainty. CPcould be recast as follows:CP*: For all propositions, x andy, if x entails y, and Jsx todegree u, then Jsy to degree v (whereu ≤v).Thus, when the Academic Skeptic employs CP (or CP*), she need not beemploying a very stringent notion of justification. That is a primarydifference between the CP-style and the Cartesian-style argument forAcademic Skepticism. Another difference is that the Cartesian-style argument concernsknowledge, whereas the CP-style argument concerns justification (towhatever degree). Nevertheless, that difference is insignificantbecause the debate about the merits of skepticism takes place withinthe evidentialist account of knowledge. Knowledge is taken to entailadequately justified assent and, hence, "knowledge" could be replacedby "adequately justified assent" in the Cartesian style argument.Let us return to the central difference between Cartesian andCP-style arguments, namely the former employs EAD while the lateremploys CP (or CP*). EAD requires that we eliminate any genuine groundsfor doubt and those include more than mere contraries (propositionswhich are such that they both cannot be true, but they both could befalse). In addition, recall that according to the Cartesian to beadequately justified in eliminating d as a ground for doubt forx, either S is adequately justified in denyingd (assenting to ~d) or S is adequatelyjustified in assenting to some neutralizing proposition, n,such that adding (n & d) to S's beliefsfails to make it the case that x is no longer adequately justified.[11] Thus, since every contrary of someproposition is a potential genuine ground for doubt in virtue ofsatisfying condition 1. in the definition of genuine doubt, EAD entailsCP but CP does not entail EAD.[12] To see that, considerany contrary, say c, of a proposition, say h. Theproposition, c, would be a potential genuine ground fordoubting h since if c were added to S'sbeliefs, h would no longer be adequately justified because S'sbeliefs would then contain a proposition, c, that entailed thedenial of h. Furthermore, the only way S couldeliminate c as a ground for doubt would be by denying it,since nothing could neutralize it. Thus, EAD has the consequence thatif S is justified in assenting to h, then S isjustified in denying every contrary of h. But that is just aninstance of CP, since (by hypothesis) h entails ~c.That CP does not entail EAD should be clear since there are grounds fordoubting h that are not contraries of h. For example,the proposition, U, considered above is a grounds fordoubting h, but h and U could bothbe true.Thus, there are two basic forms of Academic Skepticism: TheCartesian-style argument that employs the strong EAD principle and theCP-style that employs the weaker CP. Since the CP-style skeptic employsthe weaker epistemic principle, it will be best to begin by focusing onit because any criticisms of it are likely to redound to the strongerform.4. The Argument for Academic Skepticism Employing the Closure PrincipleThere appear to be only three ways that one can respond to theCP-style skeptical argument: deny at least one premise, deny that theargument is valid, or reluctantly accept the conclusion — ifneither of the first two alternatives succeeds. (I say "appear" becauseI will mention later a fourth alternative that is available to thePyrrhonian Skeptic.) The second alternative — denying thevalidity of the argument — has not been taken seriously by theanti-skeptic because it would lead to embracing an extremely severeform of skepticism. If one were to deny that modus tollens isa valid form of inference, one would also have to deny the validity of(i) disjunctive syllogism or (ii) modus ponens andcontraposition, since it is easy to transform modus tollensarguments into ones employing the other forms of inference. Hence, ifthis alternative were chosen, reasoning would apparently come to acomplete standstill. That, presumably, is why no one has ever seriouslyconsidered this alternative. So, if we are not to reluctantly embrace the conclusion, itappears as though we must reject either the first premise— an instantiation of closure — or the second premise.Consideration of CP1Let us begin an examination of CP1 and the general closure principle ofwhich it is an instantiation. The basic issue is this: Does closurehold for justified belief? Closure certainly does hold for some properties, for example, truth.If p is true and it strictly implies q, thenq is true. It just as clearly does not hold for otherproperties. If p is a belief of mine, and p strictlyimplies q, it does not follow that q is a belief ofmine. I might fail to see the implication or I might be "wired"incorrectly (from birth or as the result of an injury) or I simplymight be epistemically perverse. I might, for example, believe all ofthe axioms of Euclidean plane geometry, but fail to believe (or perhapseven refuse to believe) that the exterior angle of a triangle isequivalent to the sum of the two opposite interior angles.What about justified belief? It is easy to see that, as statedabove, CP (or CP*) is clearly false. Every necessary truth is entailedby every proposition, and we can be justified in believing a falseproposition. But one surely does not want to claim that S isjustified in believing every necessary truth wheneverS has some justified belief in a false proposition. Inaddition, some entailments might be beyond S's capacity tograsp. Finally, there might even be some contingent propositions thatare beyond S's capacity to grasp which are entailed by somepropositions that S does, indeed, grasp. And it might bethought that S is not entitled to believe anything thatS cannot grasp.But it also appears that CP can easily be repaired. We can stipulate(i) that the domain of the propositions in the generalization of CPincludes only contingent propositions that are within S'scapacity to grasp and (ii) that the entailment is "obvious" toS. The skeptic can agree to those restrictions because theskeptical scenarios are posited in such a way as to render it obviousthat our ordinary beliefs are false in those scenarios, and it is takento be a contingent claim that S is in the actual circumstancesas described in the antecedent.There is one other required clarification of the restricted versionof CP. "Justified belief" is ambiguous. It could be used to refer to aspecies of actually held beliefs — namely, those actually heldbeliefs of S that are justified. Or it could refer topropositions that S is entitled to hold — regardless ofwhether S does indeed hold them. If CP is to be acceptable,"justified belief" must be used so as to mean the latter for a reasonalready cited, i.e., belief does not transmit through entailment.We are now in a position to ask: Does the restricted form of closurehold regarding what we are entitled to believe — even ifwe don't, in fact, believe it?There appears to be a perfectly general argument for the restrictedversion. Let p entail q, and let us supposethat S is entitled to believe that p iff Shas (non-overridden) grounds that make p sufficiently likelyto be true:[13]If S is entitled to believe that p, thenS has (non-overridden) grounds that make psufficiently likely to be true. [by the supposition]If S has (non-overridden) grounds that make psufficiently likely to be true, then S has (non- overridden)grounds making q sufficiently likely to be true. [becausep entails q]If S is entitled to believe that p, thenS has (non-overridden) grounds making q sufficientlylikely to be true. [from 1,2]If S has (non-overridden) grounds making qsufficiently likely to be true, then S is entitled to believethat q. [by the supposition]Therefore, if S is entitled to believe that p,S is entitled to believe that q. [from 2,3]The supposition mentioned above seems plausible given that the debateover the merits of Academic Skepticism employs an evidentialist accountof justification. That is, the debate between the Academic Skeptic andthe Epistemist is over whether S has adequate grounds forEI-type propositions such that those grounds make psufficiently likely to be true. Premise 2 contains the key claim. In spite of the fact that theprobabilities (whether subjective or objective) transmit throughentailment, it has been challenged. Fred Dretske and others haveproduced cases in which they believe CP fails and fails preciselybecause Premise 2 in the general argument for CP is false.[14] Dretskewrites:… something's being a zebra implies that it is not amule … cleverly disguised by the zoo authorities to look like azebra. Do you know that these animals are not mules cleverly disguised?If you are tempted to say "Yes" to this question, think a moment aboutwhat reasons you have, what evidence you can produce in favor of thisclaim. The evidence you had for thinking them zebras has beeneffectively neutralized, since it does not count toward theirnot being mules cleverly disguised to look like zebras.(Dretske 1970, 1015-1016)Dretske is speaking of "knowledge" rather than beliefs to which oneis entitled, but that seems irrelevant since the issue concerns thesupposed lack of a sufficient source of evidence or reasons for theclaim that the animal is not a cleverly disguised mule. In other words,Dretske grants that S has (non-overridden) grounds that makeit sufficiently likely that the animals are zebras, but he holds that Sdoes not have (non-overridden) grounds making it sufficiently likelythat the animals are not cleverly disguised mules because S's evidencefor the former has been "effectively neutralized."The crucial thing to note about this proposed counterexample is thatit works only if the Closure Principle entails that the verysame source of evidence that justifies S in believingthat the animals are zebras must justify S inbelieving that they are not cleverly disguised mules. Since the"evidence" for the former has been "effectively neutralized," it is notavailable for the latter. Now, in response one could claim that oncethe question of whether the animals are disguised mules has beenraised, the evidence is "effectively neutralized" for both theformer and the latter, and S is no longer justified inbelieving that the animals are zebras. Thus, it could be held that thisexample could actually be used to support CP.Nevertheless, let us grant that S's evidence for the claimthat the animals are zebras cannot be used to show that they are notcleverly disguised mules. It could be argued that this would not forcegiving up Premise 2 in the general argument for CP.Such an argument could begin by recalling that Premise 2 claimedmerely that whenever S had (non-overridden) grounds that makep sufficiently likely to be true, then S has(non-overridden) grounds for making q sufficiently likely tobe true. It did not require that it was the very same groundsin both cases. Dretske's purported counterexample seems to require thatCP implies that the adequate source of evidence is the same for bothpropositions. Thus, letting "xRy" mean that xprovides an adequate evidence for y, the counter exampledepends upon assuming that if closure holds between p andq, then the evidence "path" must look like this:Pattern 1 … Rp / / …Re \ \ … RqEvidence paths specify what propositions serve as good enoughreasons, ceteris paribus, for believing other propositions.Dretske is supposing that the very same evidence, e, that Ihave for p must be adequate for q whenever pentails q. No doubt this constraint sometimes correctly portrays the relevantevidential relationships when some proposition, p, entailssome other proposition, q. For example, suppose I haveadequate evidence for the claim that Anne has two brothers, then itwould seem that the very same evidence would be adequate for believingthat Anne has at least one brother. But the defender of CP, and moreparticularly the Academic Skeptic, could point out that closure neednot require that type of evidence path in all cases in which oneproposition entails another.Two are two other possibilities for instantiating closure that arecaptured by Premise 2 that can be depicted as follows:Pattern 2 … ReRp … RqPattern 3 … Re(where e includes q) RpIn Pattern 2 cases there is some adequate evidence, e, forp; and p, itself, is the adequate evidence forq, since p strictly implies q. For example,if I have adequate evidence for believing that 2 is a prime number, Ican use that proposition as an adequate reason for believing that thereis at least one even prime. Indeed, consider any belief arrived at as aresult of deductive inference. In such a case, we legitimately inferthe entailed proposition from the conjunction of the premises thatentails it. The plausibility of the famous Gettier cases depends uponPattern 2 type cases in which closure holds. Gettier says: … for any proposition p, if S isjustified in believing p, and p entails q,and S deduces q from p and acceptsq as a result of this deduction, then S is justifiedin believing q. (Gettier 1963, 122)[15]In Pattern 3 cases the order of the evidence is reversed becauseq serves as part of the evidence for p. For example,I am justified in believing that water is present if I am justified inbelieving that there is present a clear, odorless, watery-tasting andwatery-looking fluid at standard temperature and pressure. This patternis typical of abductive inferences. In addition, there are cases inwhich some contraries of h need to be eliminated prior toh's being justified. For example, in the zebra-in-the-zoocase, if I had some reason to think that the animals were cleverlydisguised mules, then it could be argued that such a contrary wouldneed to be eliminated before I would be justified in believingthat the animals were zebras. The crucial point for the discussion here is that granting thatthere is no Pattern 1 type evidence path available to S in thezebra-in-the-zoo case does not require relinquishing premise 2 in thegeneral argument for CP. The reason is simply that CP does not entailthat there is Pattern 1 type evidence available in every case in whichp entails q. Indeed, it could be suggested that theanimals looking like zebras in a pen marked "zebras" is, ceterisparibus, adequate evidence to justify the claim that they arezebras; and once S is entitled to believe that the animals arezebras, S can, using the principle stated by Gettier,justifiably deduce that they are not cleverly disguised mules. That is,S can employ an evidence path like that depicted in Pattern 2.(See Klein 1981, 1995, and 2000a.) Further, if S hadsome reason to think that the animals were cleverly disguisedmules, then S might have to eliminate that possibility beforeshe could justifiably believe that they are zebras. In other words,S might have to employ an evidence path like the one depictedin Pattern 3. The point is that the Dretske-like counterexamples appearto depend upon the false claim that if Premise 2 in the generalargument for CP is true, then the evidential relationship between theentailing and the entailed proposition is always correctly depicted byPattern 1.In addition to the purported counterexamples to closure that we havejust examined, there are some general theories of knowledge in whichclosure fails. Robert Nozick's account of knowledge is the best suchexample. Roughly his account is this (Nozick 1981, 172-187):S knows that p iff: S believes p;p is true;if p were true, S would believe p;if p were not true, S would not believep.This account is often referred to as a tracking account of knowledgebecause whenever S knows that p, S's beliefstrack p. Think of a guided missile tracking itstarget. If the target moves left, the missile moves left. If the targetmoves right, the missile moves to the right. According to the trackingaccount of knowledge our beliefs must track the truth as a guidedmissile tracks its target. There is one important clarification of conditions 3 and 4 discussedby Nozick, namely, that the method by which S acquires thebelief must be held constant from the actual world to the possibleworld. A doting grandmother might know that her grandchild is not athief on the basis of very good evidence, but would still believe thathe wasn't a thief, even if he were, because she loves him. So, we mustrequire that the grandmother use the same method in both the actual andthe near possible worlds, for otherwise condition 4 would exclude someclear cases of knowledge. This is not the place to provide a fullexamination of Nozick's account of knowledge.[16] What is crucial forour discussion is that it is easy to see that closure will fail forknowledge in just the kind of case that the Academic Skeptic is puttingforward because of condition 4. Suppose S knows that there isa chair before her. Would she know that she is not in a skepticalscenario in which it merely appears that there is a chair? If thefourth condition were true, she would not know that because if she werein such a scenario, she would be fooled into thinking that she wasn't.Thus, either condition 4 is too strong or CP fails.There are some reasons for thinking that condition 4 is too strong.Consider a relatively simple case in which S seems to haveknowledge but condition 4 does not obtain. S looks at athermometer that is displaying the temperature as 72 degrees. Thethermometer is working perfectly and S comes to believe thatthe temperature is 72 degrees by reading the thermometer and coming tobelieve what it says. But if the temperature were not 72, suppose thatsomething would affect the thermometer in a way that made it read "72,"so that by employing the same method (looking at the thermometer andcoming to believe what it reads) S would still believe that itwas 72. (One could imagine all kinds of circumstances that would havethat causal result. A comical one: Imagine a lizard that is nowsleeping on the thermometer that would stir were the temperature torise, thus dislodging a small rock that hits the thermometer breakingthe mercury column in a way that makes the thermometer still read72.)Or consider this case in the literature: You put a glass of ice-coldlemonade on a picnic table in your back yard. You go inside and get atelephone call from a friend and talk for half an hour. When you hangup you remember that you had left the ice-cold lemonade outside exposedto the hot sun and come to believe that it isn't ice-cold anymore. Itwould seem that you could know that even if in some near world a friendof yours who just happened to be walking by noticed the glass andhappening to have a cooler full of ice with him put the glass oflemonade in the cooler to keep it ice-cold for you. Thus, if thelemonade were still ice-cold, you would believe that it wasn't. (SeeVogel 1987, 206.)The moral of these cases seems to be that S can know thatp even if there are some near possible worlds in whichp is false but S still believes that p(employing the same method of belief formation). Indeed, it couldplausibly be maintained that what is required for knowledge is that themethod of belief formation work in this world — exactly as it is— even if the method would fail were there to be some slightvariation in the actual world.Further Clarification of ClosureIn order to clarify CP further, it would be useful to contrast it witha stronger principle. I have already pointed out that in some casessome contraries of h need to be eliminated before hbecomes justified. Suppose, however, that the skeptic requires that allcontraries to h be eliminated before h is justified.That is much stronger than CP because CP is compatible withPattern 1 and Pattern 2 type evidential relationships. In neither isevery contrary to h eliminated prior to h. In Pattern 2, thecontrary of h is eliminated after h; in Pattern 1, his arrived at and its contrary is eliminated simultaneously. KeithLehrer might be appealing to the stronger principle when hewrites: … generally arguments about where the burden ofproof lies are unproductive. It is more reasonable to suppose that suchquestions are best left to courts of law where they have suitableapplication. In philosophy [emphasis added] a differentprinciple of agnoiology [the study of ignorance] is appropriate, towit, that no hypothesis should be rejected as unjustified withoutargument against it. Consequently, if the sceptic puts forth ahypothesis inconsistent with the hypothesis of common sense, then thereis no burden of proof on either side … . (Lehrer 1971,53)The passage is open to more than one interpretation, but it willserve to illustrate my point, namely that there is a very strongprinciple — call it the "Eliminate All Contraries FirstPrinciple" [EACF Principle] — which requires that allevidence paths exhibit Pattern 3 and that the denials of all contrariesto a given proposition appear prior to that proposition.If EACF were accepted, there is a really easy route to AcademicSkepticism. If it were required that the evidence, e, for somehypothesis, h, must contain the denials of all the contrariesof h, it is clear that e would have to entailh. To see that, note that (~h & p) aswell as (~h & ~p) are contraries of h,and that it is not possible for both ~(~h & p)and ~(~h & ~p) to be true and h to befalse. Thus, if the skeptic were to adopt the EACF Principle, theevidence for h would have to entail h. (See Klein1981, 100-104.) That requirement seems to be too strong for many, ifnot most, empirically contingent propositions. Hence, it could beplausibly argued that this is an inappropriate way to motivateskepticism because in so far as skepticism remains an interestingphilosophical position, the skeptic cannot impose such an outrageousdeparture from our ordinary epistemic practices.There is a related point worth mentioning. Note that even EAD,although requiring that we be able to reject or neutralize everypotential ground for doubt (i.e., a proposition satisfying condition 1.in the definition of genuine doubt), does not require what EACF does.EAD does not require that we eliminate all of the grounds for doubt(including contraries) before we are justified in believing ahypothesis. Indeed, EAD allows for the possibility that we could useh, itself, or something that h justifies as the basisfor rejecting or neutralizing some grounds for doubt.Consideration of CP2Now, with those clarifications of CP (and EAD) in mind, we can turn toCP2. It claims that we are not justified in denying the skepticalhypothesis — in other words that we are not justified inbelieving that we are not being deceived. What arguments can be givenfor CP2? It is tempting to suggest something like this: The skepticalscenarios are developed in such a way that it is supposed that wecould not tell that we were being deceived. For example, weare asked to consider that there is an Evil Genius "so powerful" thatit could (1) make me believe that there were hands when there were noneand (2) make it such that I could not detect the illusion. Butthe skeptic must be very careful here. She cannot require that in orderfor S to know (or be justified in assenting to) something, sayx, that if x were false, she would not still assentto x. We have just seen (while examining Nozick's account ofknowledge) that this requirement is too strong. So the mere fact thatthere could be skeptical scenarios in which S still believesthat she is not in such a scenario cannot provide the skeptic with abasis for thinking that she fails to know that she is not (actually) ina skeptical scenario. But even more importantly, were that arequirement of knowledge (or justification), then we have seen thatclosure would fail and, consequently, the basis for the first premisein the CP-style argument for Academic Skepticism would be forfeited.[17] In addition, we have also seen that if CP is true, and it did seemto be true, then there is one evidence pattern between entailing andentailed propositions that might prove useful to the Epistemist at thispoint in the discussion. If S could be justified in believingsome proposition that entailed the denial of the skeptical hypothesis,then S could be justified in denying that hypothesis byemploying evidence Pattern 2. Indeed, as G. E Moore suggested (1962,242), what is to prevent the Epistemist from claiming that Sis justified in denying that she is in a skeptical scenario becauseS is justified in believing that she has hands and CP is true?A plausible answer to Moore seems to be something like this: The issuethat is under dispute is whether S is justified in assentingto (or knows that) she has hands. Thus, the Epistemist cannot rejectCP2 by assuming the denial of the conclusion of the skeptical argument.All well and good. But the same sauce cooks the gander, and the skepticcannot claim as the reason for CP2 that since S isnot justified in believing that she has hands, she cannot avail herselfof that as her reason for being justified in believing that she is notin a skeptical scenario.So, what reason can the skeptic give for CP2? I do not know of onethat has been offered that is consistent with the defense of CP andthat does not beg the question. That is not to say that CP2 is false.Far from it. Perhaps it is true. The issue here is whether we arejustified in accepting or rejecting it. It seems that in order toaccept it and CP, the skeptic would have to assert that S isnot justified in believing that she has hands because evidence Pattern2 depicts one way in which S could be justified in denying theskeptical scenario. But that would beg the question because theconclusion of the CP-style argument is nothing other than S is notjustified in believing that she has hands. [18]I had mentioned earlier that although there seemed to be only threeresponses available when confronting the CP-style argument for AcademicSkepticism (accept the conclusion, reject one or both of the premises,or deny the validity of the argument), there is, in fact, a fourthalternative. That alternative is simply to point out that given therequired defense of CP1 against the counterexample proposed by Dretske,there is no good argument for CP2 (because it would beg the question),and, hence, there is no good way to motivate Academic Skepticism with aCP-style argument.Of course, the Pyrrhonian Skeptic might point to the possibilitythat there is also no good argument to the conclusion that wedo have knowledge of EI-type propositions. Some might thinkthat the Academic Skeptic wins in such a stand-off. But recall thatwhat distinguishes the Academic Skeptic from the Pyrrhonian Skeptic isthat only the Academic Skeptic assents to the claim that we cannot haveknowledge. The Pyrrhonian Skeptic withholds judgement regarding whetherwe can have knowledge. And in a stand-off, the Pyrrhonian would seem tohave appropriate attitude.This concludes the discussion of CP-style skepticism. I would nowlike to briefly consider the second form of Academic Skepticism, namelythe Cartesian-style that employs the Eliminate All Doubt Principle.Then, before we conclude our discussion of Academic Skepticism, I wouldlike to consider one quite popular response to it —contextualism.5. The Cartesian-style Argument for Academic Skepticism Employing the Eliminate All Doubt PrincipleThis section can be brief because we can apply the lessons learned inthe discussion of CP-style arguments to an evaluation of theCartesian-style arguments that employ EAD. First, it should be clearthat the general argument for the Closure Principle, consideredearlier, cannot be used as a model for a general argument for EAD. Thatargument depended crucially on the fact that h entailed~sk. (That is what provided the basis for premise 2 in thegeneral argument for CP.) As we saw, the negation of a genuine groundfor doubt need not be entailed by h. So, the skeptic has amuch harder task in motivating EAD. Nevertheless, let us grant that some argument could be provided thatmakes EAD plausible. The same dialectical issues that we haveconsidered in discussing potential counterexamples to CP will recurregarding EAD. Reconsider the zebra-in-the-zoo case. But this timeinstead of the (contrary) proposition "the animals (I am seeing) arecleverly disguised mules," consider a potential ground for doubt, i.e.,"there are cleverly disguised mules within my perceptual field," whichaccording to EAD would have to be rejected or neutralized. Now, if theevidence I had for believing that the animals are zebras wasn'tadequate to deny the former, it is certainly not adequate for thedenying the later. So the EAD skeptic will have to appeal to theanalogs of Pattern 2 and Pattern 3 type cases in order to save theprinciple from a Dretske-like counterexample. Thus, the skepticemploying EAD would be put in the same dialectical situation as theCP-style skeptic because she must provide a basis for the secondpremise in her argument for Academic Skepticism that (1) is compatiblewith her required defense of EAD against Dretske-like objections and(2) does not beg the question or appeal to a requirement that allgrounds for doubt must be eliminated prior to a proposition beingjustified.To sum up: The Cartesian-style skeptic employing EAD is in a worsedialectical position than the skeptic employing CP. Whatever problemsare associated with CP skepticism transfer to EAD skepticism and, inaddition, there appears to be no plausible general argument for EADwhile there was one for CP.6. Contextualism[19]Examining the contextualist diagnosis of Academic Skepticism and itssuggested solution will allow us to explore a question that remainsconcerning CP and EAD. It could be held that such skeptics need notemploy CP or EAD in general, but rather more restricted versions,namely merely their instantiations as they appear in their respectivearguments. The skeptic could maintain that there is something quitespecial about the skeptical hypothesis such that even though closuremight not hold in general between any entailing proposition and everyproposition it entails, it does hold between such propositions as"here's a hand" and "it does not merely appear that here is a hand."Even more strongly, the skeptic could maintain that only the Pattern 3type evidence path correctly depicts the evidential relationshipsbetween those propositions. Hence, in order to be justified inbelieving the former I must first eliminate the latter, whereto eliminate a proposition means (here) nothing more than to bejustified in denying it. The requirement that we eliminate allcontraries to some proposition, h, before we are entitled tobelieve that h is too stringent for ordinary contexts, for the reasonscited, but perhaps when engaged in philosophy we have to be justifiedin believing that the skeptical hypothesis is false before thepropositions of common sense are justified. That is essentially whatthe contextualists claim. They hold that in some contexts —philosophical ones — more stringent standards of evidence obtainthan obtain in ordinary contexts. (For defenses of contextualism, seeCohen 1987, 1988; Lewis 1996; DeRose 1992, 1995) There are two questions we should consider: Is contextualism aboutknowledge (or justified belief) the correct view to hold? If so, willit shed light on Academic Skepticism?In answering the first question, it could be argued thatcontextualism with regard to the attribution of virtually any propertyis true. (Perhaps it doesn't apply to highly technical ones that onlyoccur in one type of context.) For example, suppose that Mr. Lax saysthat Sam is happy. We discover that Lax is using "happy" to mean that aperson is happy just in case he/she has had more happy moments thanunhappy moments during a lifetime. Mr. Stringent demurs. For him, aperson is happy only if he/she hardly ever experiences an unhappymoment.Who is right about whether Sam is happy? Contextualists would saythat they both could be because they are not using "happy" with thesame criteria in mind. But it is crucial to note that given that eachperson recognizes that the other is applying different standards, Mr.Lax and Mr. Stringent can agree that, given what Lax means,Sam is happy and that, given what Stringent means, Sam is nothappy.Now, of course, we cannot employ any standards we pleaseand still be speaking a common language. For example, Mr. Lax cannotlegitimately lower the standards so as to make it the case that Sam ishappy simply because he once was happy for a very short periodand, similarly, Mr. Stringent cannot require that Sam is happy only ifit is logically impossible that Sam experience an unhappymoment. There is a limited range, albeit rather wide, of appropriatestandards for the application of a term.The predicates "having knowledge," "having adequate evidence,""being justified," and the like, do appear to be similar to most otherpredicates in this respect: Within a wide but non-arbitrary range ofstandards, speakers can legitimately demand that S have moreor less of the relevant evidence for p before they will agreethat "S knows that p" or "S has adequateevidence for p." So, the answer to the first question aboutthe truth of contextualism seems to be: Contextualism about knowledgeattributions is correct. It is just one instance of the general truththat standards for the application of a term vary within a wide butnon-arbitrary range as determined by various features of thecontext.Let us turn to the second and much more philosophicallyinteresting question: Does the truth of this version of contextualismshed much, if any, light on Academic Skepticism? If it did, then thecorrect way to diagnose the dispute between the Academic Skeptic andthe Epistemist would be to note that the Epistemist is using a laxstandard and the skeptic a more stringent one. Having one's ordinarycake is compatible with eating one's skeptical cake because in theordinary context we do have knowledge, but as standards rise to thoseemployed by the skeptics, we do not have knowledge.In response, it might be objected that this is not the properdiagnosis of the disagreement between the Academic Skeptic and theEpistemist. What the Academic Skeptic seems to be claiming is that wedo not know what we ordinarily claim to know. We don't know EI-typepropositions. That is, the Academic Skeptic claims that our ordinaryknowledge claims are false. If she is merely claiming that onher standards we don't know, the skeptic's claims — likethose of Mr. Stringent — can be granted and then promptly ignoredbecause nothing that we formerly believed that we knew turns out not tohave been known. The scope of our knowledge or justified beliefs in theordinary context is left intact.Thus, the parallel with the case of Sam's putative happiness seemsto break down. In that case, Mr. Stringent would grant that Mr. Lax iscorrect given what Lax meant by "happy." But the AcademicSkeptic will not grant that the Epistemist is correct when he assertsthat he has knowledge. The skeptic reasons that the Epistemist doesn'tknow that h, even given what the Epistemist means by"know," because the Epistemist's justification for hisn't good enough. Indeed, the Academic Skeptic employing CP (or thestronger EAD) thinks that there cannot be any evidence for~sk no matter how low the standards are set; thus, hcould not be known.The issue seems to boil down to this: In the ordinary context is ittrue — as the Academic Skeptic claims — that in order toknow that there are hands, we must first eliminate the skepticalhypothesis?The Epistemist could argue that this is not required. Suppose we arelooking at Dretske's zebras and someone asks whether we have eliminatedthe possibility that those are cleverly disguised aliens from someplanet thousands of light years from our solar system? Or that they arenot super-robots newly invented by some very clever third graders inMrs. Johnson's English class? Or that they are not members of the losttribe of Israel disguised as zebras who have been hiding out from theAssyrians since the 8th century BC.Those are so far-fetched, the Epistemist could claim, that even ifsomeone advancing those alternatives happens to believe them, thereappears to be no reason why one should have to rise to the bait andeliminate those alternatives prior to being justified in believing thatthe animals are zebras. The Epistemist could continue by claiming thatthe skeptical hypothesis — that we are not in the actual worldbut rather in one which seems identical to it — is just as, orpossibly even more, farfetched.Thus the Epistemist could argue that try as she might, the AcademicSkeptic cannot impose the burden of eliminating a farfetched hypothesismerely by raising it, even were she to believe it. On the other hand,the Epistemist could agree that in Dretske's zebra-in-the zoo case, ifthere really were some evidence, however slight, for the claim that theanimals are painted mules, then Mr. Stringent might be able tolegitimately require that S rule out that possibility prior tobeing justified in believing that the animals are zebras. But absentany evidence of that sort, the skeptic's requirements will fall on deafears. In parallel fashion, if there really were some evidence, howeverslight, that there is an evil genius making it merely appear that thereare hands, then, perhaps the Academic Skeptic could legitimatelyrequire that S eliminate that possibility prior to beingjustified in believing that there are hands.Put another way: The Epistemist can claim that the range of relevantalternatives is bounded by those propositions for which there is some,even minimal, evidence. The Epistemist will claim that it is acontext-invariant feature of knowledge attributions that the relevantevidence does not include the denial of contraries for which there isno evidence whatsoever. The issue seems to be whether our ordinaryknowledge claims are true — not whether they would betrue in some context with requirements more stringent that thoseordinarily applied.7. PyrrhonismAs mentioned at the beginning of this essay, what distinguishesPyrrhonian Skepticism from Academic Skepticism is that the former doesnot deny that we can have knowledge of what I have called EI-typepropositions. They also would not assent to the Epistemist's claim thatwe can have such knowledge. Let us see how they arrived at thatposition. To deny something is merely to assent to its negation. Since thePyrrhonians took assent, i.e., the pro-attitude required for knowledge,to involve a kind of certainty that the matter had been finally andfully resolved, they did not assent to what they took to be non-evidentpropositions.In distinguishing Pyrrhonism from the Academic Skeptics (inparticular, Carneades and Cleitomachus), Sextus writes in Outlinesof Pyrrhonism, [PH]:… although both the Academics and the [Pyrrhonian]Skeptics say that they believe some things, yet here too the differencebetween the two philosophies is quite plain. For the word "believe" hasdifferent meanings; it means not to resist but simply to follow withoutany strong impulse or inclination, as the boy is said to believe histutor; but sometimes it means to assent to a thing of deliberate choiceand with a kind of sympathy due to strong desire, as when theincontinent man believes him who approves of an extravagant mode oflife. Since, therefore, Carneades and Cleitomachus declare that astrong inclination accompanies their credence … while we saythat our belief is a matter of simply yielding without any consent,here too there must be difference between us and them.(PH I:230)So, the Pyrrhonians would not assent to non-evident propositions. Ofcourse, a crucial issue concerns the scope of the non-evident. To tryto resolve that is beyond the scope of this essay (but see Burnyeat& Frede 1997). For our discussion we can suppose that a sufficientcondition for some proposition being non-evident obtains whenever therecan legitimately be disagreement about it. And, taking the cue from ourdiscussion of Academic Skepticism, I think we can also safely stipulatethat there can be legitimate disagreement about some proposition ifthere is some evidence for it and some evidence against it. So, thequestion is whether the proposition S can have knowledge of EI-typepropositions can be the subject of legitimate disagreement.Putting the matter that way seems to make the answer obvious. Thereare arguments for Academic Skepticism which have some plausibility, andsome plausible objections to those arguments that support theEpistemist's view. Plausible arguments for something constitute someevidence for it. So, we can safely conjecture both that it is notevident that we can have knowledge of EI-type propositions and that itis not evident that such propositions necessarily fall outside ourcognizance. Thus, the primary question then becomes this: What promptedthe Pyrrhonian to withhold assent to all non-evident propositions?The answer is that they found over and over again that neitherexperience nor reason was able to settle disputes about thenon-evident. But the Pyrrhonians did not eschew what they called"appearances" or reasoning. Quite the contrary, the Greek for "skeptic"is closely related to the verb "sképtomai" which means"to inquire." Thus, calling oneself a Pyrrhonian Skeptic did not implya disregard for inquiry or reasoning. Indeed, the modes, to bediscussed later, were not designed to inhibit reasoning. Rather, theywere designed to assist the Pyrrhonian in continuing to inquire byshielding her from the disquieting state of dogmatism.Pyrrhonian skepticism was thus a way of life without assent. Assuch, it has been ridiculed. The Pyrrhonian was likened to someone withAlzheimer's — surviving only if someone else were around to savehim from all sorts of perils: falling into pits, being attacked by adog or run over by a chariot. That caricature seems to miss the pointthat the Pyrrhonian only withheld assent with regard to the non-evident propositions.[20] Assent to what was evident (i.e., whatappears to be) or a weaker pro-attitude toward the non-evident werecommonplace.As mentioned above, the Pyrrhonians would practice what they calledthe "modes" in order to try to assure that they were not "perturbed" byassenting. Like piano exercises for the fingers that would result insemi-automatic responses to the printed notes on a sheet of music, themodes were mental exercises that would result in semi-automaticresponses to claims being made by the dogmatists — those whoassented to the non-evident.The Pyrrhonians believed that (but would not have assented to theclaim that) there were two potential sources of knowledge: perceptionand reasoning. When the results of perception were introduced to settlea non-evident matter — say the actual color of an object(as opposed to how it appeared to someone), they would point out someor all of the following (Sextus Empiricus, PHI:40-128):Members of different species of animals probably perceivecolors quite differently because their eyes are constructeddifferently.Members of the same species would have differentperceptions of the color depending upon such things as the condition oftheir eyes, the nature of the medium of perception (varying lightconditions for example), and the order in which objects wereperceived.Being reminded of the relativity of perception could incline a personto refrain from assenting to judgements of perception, when thosejudgements were about the "real" properties of the objects. As Sextuswrote: … When we question whether the underlying object issuch as it appears, we grant the fact that it appears, and our doubtdoes not concern the appearance itself, but the account given of theappearance. (PH I:19-20)Now, perhaps a careful analysis of what is meant by "real" propertiescoupled with a Cartesian-like answer to some of the doubts raisedearlier in the Meditations would suffice to respond to thePyrrhonian concerning the relativity of our senses. For example, if wetook the "real" color of objects to be that property (or state) of theobject, whatever it is, that produces perceptions of a certain sort inhumans under "normal" circumstances and if we could distinguish (asDescartes suggested) normal from abnormal circumstances, then we mighthave a basis for resisting the Pyrrhonian modes concerning perception.But be that as it may, whether we can have knowledge of EI-typepropositions is not a matter that is potentially resolvable by directappeal to our senses. It will only be resolved if either the Epistemistor the Academic Skeptic has a compelling argument. Thus, the issue hereis whether reasoning can settle matters. The Pyrrhonians thought that there were modes which could inducewithholding assent to the results of reasoning. It is to those modesthat we should turn.Perhaps the most influential passage in the corpus of the Pyrrhonianliterature is a section from PH entitled"Five Modes of Agrippa." Although the chapter title mentions fivemodes, two of them repeat those found elsewhere and are similar to theones just discussed concerning perception. They are the modes ofdiscrepancy and relativity and are important because they provide thebackground for understanding the description of the three modesconcerning reasoning. Specifically, it is presumed that the relevantobject of inquiry is subject to legitimate dispute and that reasoningis employed to resolve the dispute. The issue before us then is whetherreasoning can legitimately lead to assent. Sextus writes:The Mode based upon regress ad infinitum is thatwhereby we assert that the thing adduced as a proof of the matterproposed needs a further proof, and this again another, and so onad infinitum, so that the consequence is suspension [ofassent], as we possess no starting-point for our argument … Wehave the Mode based upon hypothesis when the Dogmatists, being forcedto recede ad infinitum, take as their starting-point somethingwhich they do not establish but claim to assume as granted simply andwithout demonstration. The Mode of circular reasoning is the form usedwhen the proof itself which ought to establish the matter of inquiryrequires confirmation derived from the matter; in this case, beingunable to assume either in order to establish the other, we suspendjudgement about both. (PHI:166-169)The question is this: Supposing that the dogmatist assents tosomething, say p, on the basis of a reason, say q,and gives r as his reason for q, etc., how should thePyrrhonian react in order to avoid the snares of dogmatism? Thesuggestion in this passage appears to be to force the dogmatist intoeither an apparently never ending regress or an arbitrary assertion orbegging the question. This strategy seems to be based upon the claim that there are (only)three possible patterns which any instance of reasoning can take. Iwill call the first pattern "infinitism." Today we commonly refer tothe second account as "foundationalism." Finally, I will refer to thethird possibility as "coherentism."The so-called "regress problem," can be stated briefly in this way:There are only three possible patterns of reasoning. Either the processof producing reasons stops at a purported foundational proposition orit doesn't. If it does, then the reasoner is employing afoundationalist pattern. If it doesn't, then either the reasoning iscircular, or it is infinite and non-repeating. There are no othersignificant possibilities.[21] Thus, if none of these forms of reasoningcan properly lead to assent, then no form can.So, we must look briefly at the reasons that a Pyrrhonian might havefor thinking that foundationalism, coherentism and infinitism areinherently incapable of providing an adequate basis for assent.[22]8. The Mode to Respond to the FoundationalistThe Pyrrhonian is not (and cannot consistently be) assenting to theclaim that foundationalism is false. Rather, a Pyrrhonian employingthis mode would be attempting to reassure herself (and perhaps show theEpistemist) that the so-called foundational proposition stands in needof further support. In other words, the Pyrrhonian believes that afoundationalist cannot rationally practice his foundationalism becauseit inevitably leads to arbitrariness — i. e., assenting to aproposition which can legitimately be questioned but is, nevertheless,assented to without rational support. So, how could the Pyrrhonian proceed? To begin to answer thatquestion it is important to note that foundationalism comes in manyforms. But all forms hold that the set of propositions can bepartitioned into basic and non-basic propositions. Basicpropositions have some autonomous bit of warrant that does notdepend (at all) upon the warrant of any other proposition.[23]Non-basic propositions depend (directly or indirectly) uponbasic propositions for all of their warrant.Suppose that an inquirer, say Fred D'Foundationalist, has given somereasons for his beliefs. Fred offers q (where q couldbe a conjunction) for his belief that p, and he offersr (which could also be a conjunction) as his reason forq. Etc. Now, being a foundationalist, Fred finally offers somebasic proposition, say b, as his reason for the immediatelypreceding belief. Sally D'Pyrrhonian asks Fred why he believes thatb is true. Sally adds the "is true" to make clear to Fred thatshe is not asking what causes Fred to believe that b. Shewants to know why Fred thinks that b is true. Now, Fred couldrespond by giving some reason for thinking that b is true evenif b is basic, because basic propositions could have somenon-autonomous warrant that depends upon the warrant of otherpropositions. But that is merely a delaying tactic since Fred is not acoherentist. In other words, he might be able to appeal to theconjunction of some other basic propositions and the non-basicpropositions that they warrant as a reason for thinking that bis true. But Sally D'Pyrrhonian will ask whether he has any reason thatdoes not appeal to another member in the set of basic propositions forthinking that each member in the set is true. If he says that he hasnone, then he has forfeited his foundationalism because he is really acloset coherentist. Being true to his foundationalism, he must thinkthat there is some warrant that each basic proposition has that doesnot depend upon the warrant possessed by any other proposition.The crucial point to note here is that Sally can grant that theproposition has autonomous warrant but continue to press the issuebecause she can ask Fred whether the possession of autonomous warrantis at all truth conducive. That is, she can ask whether a propositionwith autonomous warrant is, ipso facto, at all likely to betrue. If Fred says "yes," then the regress will have continued. For hehas this reason for thinking that b is true: "b hasautonomous warrant and propositions with autonomous warrant aresomewhat likely to be true." If he says "no" then Sally can point outthat he is being arbitrary since she has asked why he thinks b is trueand he has not been able to provide an answer.Let us look at an example. Often it is held that first-personintrospective reports are basic because they have some "privileged"status. My basic reason for thinking that there is an "external" objectof a certain sort is that I am having an experience of a certain sort.Now, what Sally should ask is this: "Why do you think you are having anexperience of that sort? Or, again to emphasize that she is not askingfor an explanation of the etiology of Fred's belief that he is havingan experience of that sort, she could ask: "Why do you think that theproposition ‘I am having an experience of a certain sort’is true?"The dilemma is that either Fred has a reason for thinking thatproposition is true or he doesn't. If he does, then the regress has notstopped — in practice. If he doesn't, then he is beingarbitrary — in practice.Once again, it is crucial to recall that Pyrrhonians arenot claiming that foundationalism is false. They could grantthat some propositions do have autonomous warrant which istruth-conducive and that all other propositions depend for some oftheir warrant upon those basic propositions. What lies at the heart oftheir view is that there is a deep irrationality in being a practicingself-conscious foundationalist. The question to Fred can be put thisway: On the assumption that you cannot appeal to any other proposition,do you have any reason for thinking that b is true? Fred notonly won't have any such reason for thinking b is true, giventhat assumption, he cannot have one (if he remains true to hisfoundationalism). Arbitrariness seems inevitable. Of course,foundationalists typically realize this and, in order to avoidarbitrariness, tell some story (for example, about privileged access)that, if true, would provide a reason for thinking basic propositionsare at least somewhat likely to be true. But then, the regress ofreasons has continued.9. The Mode to Respond to the CoherentistAt its base, coherentism holds that there are no propositions withautonomous warrant. But it is important to note that coherentism comesin two forms. What I choose to call the "warrant-transfer form"responds to the regress problem by suggesting that the propositions arearranged in a circle and that warrant is transferred within the circle— just as basketball players standing in a circle pass the ballfrom one player to another. (See Sosa 1980, and BonJour 1978.) I could,for example, reason that it rained last night by calling forth mybelief that there is water on the grass and I could reason that thereis water (as opposed to some other liquid, say glycerin, that lookslike water) on the grass by calling forth my belief that it rained lastnight. Long ago, Aristotle pointed out that this process of reasoning couldnot resolve matters. As he put it: This is a "simple way of provinganything" (Posterior Analytics, I, iii, 73a5). Thepropositions in the circle might be mutually probability enhancing, butthe point is that we could just as well have circular reasoning to theconclusion that it did not rain last night because the liquid is notwater and the liquid is not water because it did not rain last night.In this fashion anything could be justified — too simply! It isultimately arbitrary which set of mutually probability enhancingpropositions we believe because there is no basis for preferring oneover the other.The warrant-transfer coherentist could reply to this objection byclaiming that there is some property, P, in one of the twocompeting circles that is not present in the other and the presence ofthat property makes the propositions in one and only one of the circlesworthy of assent. For example, in one and only one of the circles arethere propositions that we actually believe, or perhaps believe spontaneously.[24] But, then, it seems clear that thewarrant-transfer coherentist has adopted a form of foundationalismsince he is now claiming that all and only the propositions in circleswith P have some autonomous bit of warrant. And, all that wehave said about the dilemma facing the foundationalist transfersimmediately. Is the possession of P truth conducive or not? Ifit is … You can see how that would go.So much for the warrant-transfer version of coherentism. The secondform of coherentism, what we can call the "warrant-emergent form" doesnot imagine the circle as consisting of propositions that transfertheir warrant from one proposition to another. Rather warrant for eachproposition in the circle obtains because it is a member of a set ofmutually probability enhancing propositions. Coherence itself is theproperty in virtue of which each member of the set of propositions haswarrant. Warrant emerges all at once, so to speak, from the web-likestructure of the set of propositions. The coherentist can then arguethat the fact that the propositions cohere provides each of them withsome prima facie credibility.This might initially seem to be a more plausible view since itavoids the circularity charge. But, aside from the problem that are toomany competing circles that are coherent, the coherentist has, onceagain, embraced foundationalism. The coherentist is now explicitlyassigning some initial positive warrant to all of the individualpropositions in a set of coherent propositions that does not dependupon the warrant of any other proposition in the set. In other words,he is assigning to them what we have called the autonomous bit ofwarrant and, once again, the dilemma facing the foundationalistreturns.10. The Mode to Respond to the InfinitistThe third mode is designed to provide the Pyrrhonian with a way ofresponding to a dogmatist who assents to some EI-type proposition,x, and ceaselessly provides new answers to the question "Whatreason do you have for x?" Since there is always anotherreason, one that has not already been employed, that needs to be givenfor any offered reason, assenting to x would be inappropriate. Sincethe Pyrrhonian (or the Epistemist) does not know either whether thereis such an infinite set of reasons available or whether there is nosuch set available, withholding assent to the proposition thatknowledge of EI-type propositions is possible seems appropriate. For those reasons, infinitism (as far as I can tell) has never beenseriously considered as a model of reasoning suitable for the dogmatistbecause it is obvious that it cannot provide a model of reasoning thatcould lead to assent. A disputed proposition could never be fullyjustified for whenever a reason is provided the infinitist is committedto thinking that in order to settle the matter another, as yet"unused," reason must be provided. Since that process can never becompleted, infinitism cannot provide the dogmatist with a model thatwill settle matters.[25]11. The Overall Effect of the ModesIt appears that the Pyrrhonian has a viable strategy for resistingdogmatism because no process of reasoning is such that assent —that is, holding that the matter in question has been settled —is the appropriate attitude to have toward any non-evident proposition.BibliographyAudi, R., 1988, Belief, Justification and Knowledge,Belmont, California: Wadsworth.BonJour, L., 1978, "Can Empirical Knowledge Have a Foundation?"American Philosophical Quarterly, 15/1, 1-13.------, 1985, The Structure of Empirical Knowledge,Cambridge, Mass: Harvard University Press.Burnyeat, M., and Frede, M., 1997, The Original Sceptics: AControversy, Indianapolis/Cambridge: Hackett Publishing Co.Cohen, S., 1987, "Knowledge, Context and Social Standards,"Synthese, 73, 3-26.-----, 1988, "How to be a Fallibilist," Philosophical Perspectives,2, 91-123.DeRose K., 1992, "Contextualism and Knowledge Attributions,"Philosophy and Phenomenological Research, 52, 913-929.-----, 1995, "Solving the Skeptical Problem," Philosophical Review,104, 1-52.DeRose, K., and Warfield, T. (eds.), 1999, Skepticism: AContemporary Reader, New York and Oxford: Oxford UniversityPress.Descartes, R., Meditations on First Philosophy, in E.Haldane and G. Ross (eds.), Philosophical Works of Descartes,Volume 1, Dover Publications, 1931.Dretske, F., 1970, "Epistemic Operators," Journal ofPhilosophy, 67, 1007-1023.Gettier, E., 1963, "Is Knowledge True Justified Belief?"Analysis, 23, 121-123.Irwin, W., 2002, The Matrix and Philosophy, OpenCourt.-----, 2005, More Matrix and Philosophy, Open Court.Klein, P., 2003, "How a Pyrrhonian Skeptic Might Respond toAcademic Skepticism" in The Skeptics: Contemporary Essays,Steven Luper (ed.), Ashgate Press, 75-94-----, 2002, "Skepticism" in The Oxford Handbook ofEpistemology, P. Moser (ed.), Oxford: Oxford University Press,336-361.-----, 2000a, "Contextualism and the Real Nature of AcademicSkepticism," Philosophical Issues, 10, 108-116.-----, 2000b, "Why Not Infinitism?" Epistemology: Proceedingsof the Twentieth World Congress in Philosophy, R. Cobb-Stevens(ed.), 2000, vol 5, 199-208.-----, 1999, "Human Knowledge and the Infinite Regress of Reasons,"Philosophical Perspectives, 13, J. Tomberlin (ed.),Atascadero: Ridgeview Press, 297-325.-----, 1995, "Skepticism and Closure: Why the Evil Genius ArgumentFails," Philosophical Topics, 23/1 (Spring): 213-236.-----, 1981, Certainty: A Refutation of Scepticism,Minneapolis: University of Minnesota Press.Lehrer, K., 2000, Theory of Knowledge, Boulder, Colorado:Westview Press, second edition.-----, K., 1971, "Why Not Skepticism?"The PhilosophicalForum, 2/3, 283-298. (Page reference is to the reprint in TheTheory of Knowledge, L. Pojman (ed.), Belmont, CA: WadsworthPublishing Company, 1993.)-----, 1997, Self-Trust: A Study of Reason, Knowledge andAutonomy, Oxford: Clarendon Press, Oxford University Press.Lewis, D., 1996, "Elusive Knowledge,"Australian Journal ofPhilosophy, 74, 549-67.Luper-Foy, S., (ed.), 1987, The Possibility of Knowledge,Totowa, NJ: Rowman & Littlefield.Malcolm, N., 1963, Knowledge and Certainty, EnglewoodCliffs, NJ: Prentice-Hall.Moore, G.E., 1962, "Certainty" in Philosophical Papers,New York, NY: Collier Books.Nozick, R., 1981, Philosophical Explanations, Cambridge,Massachusetts: Harvard University Press.Radford, C., 1966, "Knowledge -- By Example," Analysis,27, 1-11.Sextus Empiricus, Outlines of Pyrrhonism[PH], R. G. Bury,trans., Cambridge, Massachusetts: Harvard University Press, 1967.Sextus Empiricus, Against the Logicians, R. G. Bury,trans., Cambridge, Massachusetts: Harvard University Press, 1967.Sosa, E., 1980, "The Raft and the Pyramid," Midwest Studies inPhilosophy, 5, 3-25.Stroud, B., 1984, The Significance of PhilosophicalScepticism, Oxford: Clarendon Press.Unger, P., 1975, Ignorance: A Case for Scepticism, Oxford:Oxford University Press.Vogel, J., 1987, "Tracking, Closure and Inductive Knowledge" inLuper-Foy 1987.Wittgenstein, L., 1969, On Certainty, New York: HarperTorchbooks.Other Internet ResourcesLinks to papers on Skepticism, in the Epistemology Research Guide,maintained by Keith Korcz (U. Louisiana/Fayetteville)Related Entries Descartes, René: epistemology | justification, epistemic: coherentist theories of | justification, epistemic: foundationalist theories of | justification, epistemic: internalist vs. externalist conceptions of | skepticism: ancientAcknowledgmentsI wish to thank Anne Ashbaugh and Laurence BonJour for their help withthis entry. I should also note that some parts of the entry rely uponand, in some cases, significantly repeat sections of Klein 2002. I alsorelied on parts of Klein 1995, 1999, 2000a, and 2003. Copyright © 2005 byPeter Klein <pdklein@rci.rutgers.edu> |
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