Casullo, Albert

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MODERN ACCOUNTSArmstrong, D. M. Belief, Truth, and Knowledge. Cambridge,U.K.: Cambridge University Press, 1973.Audi, Robert. Epistemology: A Contemporary Introduction to theTheory of Knowledge. 2nd ed. New York: Routledge, 2003.Austin, John. “Other Minds.” In his Philosophical Papers.London: Oxford University Press, 1962.Ayer, A. J. The Foundations of Empirical Knowledge. London:Macmillan, 1940.Ayer, A. J. The Problem of Knowledge. London: Macmillan,1956. Chs. 1–2.BonJour, Lawrence. The Structure of Empirical Knowledge.Cambridge, MA: Harvard University Press, 1985.Brewer, Bill. Perception and Reason. Oxford: Clarendon Press,2002.Chisholm, Roderick. The Foundations of Knowing.Minneapolis: University of Minnesota Press, 1982.Chisholm, Roderick M. Perceiving: A Philosophical Study.Ithaca, NY: Cornell University Press, 1957. Part I.Dretske, Fred. Seeing and Knowing. London: Routledge andKegan Paul, 1969.Foley, Richard. Working without a Net. New York: OxfordUniversity Press, 1993.Goldman, Alvin. Epistemology and Cognition. Cambridge, MA:Harvard University Press, 1986.Harman, Gil. Thought. Princeton, NJ: Princeton UniversityPress, 1973.Hintikka, Jaakko. Knowledge and Belief. Ithaca, NY: CornellUniversity Press, 1962.Klein, Peter. Certainty: A Refutation of Scepticism. Minneapolis:University of Minnesota Press, 1981.Lehrer, Keith. Theory of Knowledge. Boulder, CO: WestviewPress, 1990.Lewis, C. I. Mind and the World-Order. New York: Scribners,1929. Ch. 9.Malcolm, Norman. Knowledge and Certainty. Englewood Cliffs,NJ: Prentice Hall, 1963.Moore, G. E. Philosophical Papers. London: Allen and Unwin,1959.Plantinga, Alvin. Warrant and Proper Function. Oxford: OxfordUniversity Press, 1993.Popper, Karl R. Conjectures and Refutations. London:Routledge, 1963. See the introduction.Prichard, H. A. Knowledge and Perception. Oxford: ClarendonPress, 1950.Russell, Bertrand. Problems of Philosophy. London: Williamsand Norgate, 1912. Chs. 5, 13.Ryle, Gilbert. The Concept of Mind. London: Hutchinson, 1949.Ch. 2.Sosa, Ernest. Knowledge in Perspective: Selected Essays inEpistemology. Cambridge, U.K.: Cambridge University Press,1991.Wilson, John Cook. Statement and Inference. Oxford:Clarendon Press, 1926. Part 1, Chs. 2, 4; Part II, Chs. 1–3.Woozley, A. D. Theory of Knowledge: An Introduction. London:Hutchinson, 1949. Ch. 8.Anthony Quinton (1967)Bibliography updated by Benjamin Fiedor (2005)knowledge andmodalityThe prominence of the modalities (i.e., necessity andcontingency) in epistemological discussions is due to theinfluence of Immanuel Kant (1965), who maintainedthat:(1) All knowledge of necessary propositions is a pri-ori; and(2) All propositions known a priori are necessary.Saul Kripke (1971, 1980) renewed interest in Kant’saccount of the relationship between the a priori and thenecessary by arguing that some necessary propositionsare known a posteriori and some contingent propositionsare known a priori. A cogent assessment of the contro-versy requires some preliminary clarification.The distinction between necessary and contingentpropositions is metaphysical. A necessarily true (false)proposition is one that is true (false) and cannot be false(true). The distinction between a priori and a posterioriknowledge is epistemic. S knows a priori that p just incase: (a) S knows that p; and (b) S’s justification forbelieving that p does not depend on experience. Condi-tion (b) is controversial. On the traditional reading, (b) isequivalent to (c): S’s belief that p is nonexperientially jus-tified. Hilary Putnam (1983) and Philip Kitcher (1983),however, argue that (b) is equivalent to (d): S’s belief thatp is nonexperientially justified and cannot be defeated byexperience. Albert Casullo (2003) rejects the Putnam-Kitcher reading on the grounds that it yields an analysisof a priori knowledge that excludes the possibility thatsomeone knows a posteriori a proposition that can beknown a priori.The expression “knowledge of necessary proposi-tions” in (1) is ambiguous. The following definitionsremove the ambiguity:(A) S knows the general modal status of p just in caseS knows that p is a necessary proposition (i.e.,either necessarily true or necessarily false) or Sknows that p is a contingent proposition (i.e.,either contingently true or contingently false);(B) S knows the truth value of p just in case S knowsthat p is true or S knows that p is false (assumingtruth is always bivalent);(C) S knows the specific modal status of p just in caseS knows that p is necessarily true or S knows thatp is necessarily false or S knows that p is contin-gently true or S knows that p is contingently false.KNOWLEDGE AND MODALITYENCYCLOPEDIA OF PHILOSOPHY100 • 2 n d  e d i t i o neophil_K  11/2/05  3:40 PM  Page 100(A) and (B) are logically independent. One can know thatGoldbach’s Conjecture is a necessary proposition but notknow whether it is true or false. Alternatively, one canknow that some mathematical proposition is true but notknow whether it is a necessary proposition or a contin-gent proposition. (C), however, is not independent of (A)and (B). One cannot know the specific modal status of aproposition unless one knows both its general modal sta-tus and its truth value.(1) is crucial for Kant, because it is the leading prem-ise of his only argument in support of the existence of apriori knowledge:(1) All knowledge of necessary propositions is a pri-ori.(3) Mathematical propositions, such as that 7 + 5 =12, are necessary.(4) Therefore, knowledge of mathematical proposi-tions, such as that 7 + 5 = 12, is a priori.(1), however, is ambiguous. There are two ways of read-ing it:(1T) All knowledge of the truth value of necessarypropositions is a priori, or(1G) All knowledge of the general modal status of nec-essary propositions is a priori.The argument is valid only if (1) is read as (1T). Kant,however, supports (1) with the observation that althoughexperience teaches that something is so and so, it does notteach us that it cannot be otherwise. Taken at face value,this observation states that experience teaches us that aproposition is true and that experience does not teach usthat it is necessary. This supports (1G), not (1T).Kripke rejects (1) by offering examples of necessarytruths that are alleged to be known a posteriori. First, hemaintains that if P is an identity statement betweennames, such as “Hesperus = Phosphorus,” or a statementasserting that an object has an essential property, such as“This table is made of wood,” then one knows a priorithat:(5) If P then necessarily P.Second, he argues that because one knows by empiricalinvestigation that Hesperus = Phosphorus and that thistable is made of wood, one knows a posteriori that:(6) P.Kripke concludes that one knows by modus ponens that:(7) Necessarily P.(7) is known a posteriori because it is based on (6), whichis known a posteriori.How do Kripke’s examples bear on (1)? Once again,a distinction must be made between (1G) and (1T).Kripke’s examples, if cogent, establish that (1T) is false:They establish that one knows a posteriori that some nec-essary propositions are true. They do not, however, estab-lish that (1G) is false: They do not establish that oneknows a posteriori that some necessary propositions arenecessary. It may appear that Kripke’s conclusion that onehas a posteriori knowledge that necessarily P entails that(1G) is false. Here a distinction must be made between(1G) and:(1S) All knowledge of the specific modal status of nec-essary propositions is a priori.Kripke’s examples establish that (1S) is false: They estab-lish that one knows a posteriori that some necessarypropositions are necessarily true. Because knowledge ofthe specific modal status of a proposition is the conjunc-tion of knowledge of its general modal status and knowl-edge of its truth value, it follows from the fact that one’sknowledge of the truth value of P is a posteriori that one’sknowledge of its specific modal status is also a posteriori.However, from the fact that one’s knowledge of the spe-cific modal status of P is a posteriori, it does not followthat one’s knowledge of its general modal status is also aposteriori.(1G) has not gone unchallenged. Kitcher (1983)argues that even if knowledge of the general modal statusof propositions is justified by nonexperiential evidence,such as the results of abstract reasoning or thought exper-iments, it does not follow that such knowledge is a prioribecause the nonexperiential justification in question canbe defeated by experience. Casullo (2003) rejects (1G) onthe grounds that the Kantian contention that experiencecan provide knowledge of only the actual world overlooksthe fact that much practical and scientific knowledgeinvolves counterfactual conditionals, which provideinformation that goes beyond what is true of the actualworld.Kripke also argues that some contingent truths areknown a priori. His examples are based on the observa-tion that a definite description can be employed to fix thereference—as opposed to give the meaning—of a term.Consider someone who employs the definition descrip-tion “the length of S at t0” to fix the reference of theexpression “one meter.” Kripke maintains that this personknows, without further empirical investigation, that S isone meter long at t0. Yet the statement is contingentKNOWLEDGE AND MODALITYENCYCLOPEDIA OF PHILOSOPHY2 n d  e d i t i o n • 101eophil_K  11/2/05  3:40 PM  Page 101because “one meter” rigidly designates the length that isin fact the length of S at t0 but, under different conditions,S would have had a different length at t0. In reply, AlvinPlantinga (1974) and Keith Donnellan (1979) contendthat, without empirical investigation, the reference fixerknows that the sentence “S is one meter long at t0”expresses a truth, though not the truth that it expresses.Gareth Evans (1979) disputes this contention.B i b l i o g r a p h yCasullo, Albert. A Priori Justification. New York: OxfordUniversity Press, 2003.Donnellan, Keith S. “The Contingent A Priori and RigidDesignators.” In Contemporary Perspectives on the Philosophyof Language, edited by P. French et al. Minneapolis:University of Minnesota Press, 1979.Evans, Gareth. “Reference and Contingency.” Monist 62 (1979):161–189.Kant, Immanuel. Critique of Pure Reason. Translated byNorman Kemp Smith. New York: St. Martin’s Press, 1965.Kitcher, Philip. The Nature of Mathematical Knowledge. NewYork: Oxford University Press, 1983.Kripke, Saul. “Identity and Necessity.” In Identity andIndividuation, edited by M. K. Munitz. New York: New YorkUniversity Press, 1971.Kripke, Saul. Naming and Necessity. Cambridge, MA: HarvardUniversity Press, 1980.Plantinga, Alvin. The Nature of Necessity. Oxford: OxfordUniversity Press, 1974.Putnam, Hilary. “‘Two Dogmas’ Revisited.” In Realism andReason: Philosophical Papers. Vol. 3. Cambridge, U.K.:Cambridge University Press, 1983.Albert Casullo (1996, 2005)knowledge and truth,the value ofQuestions concerning the value of knowledge and truthrange from those that suggest complete skepticism aboutsuch value to those that reflect more discriminating con-cerns about the precise nature of the value in questionand the comparative judgment that one of the two ismore valuable than the other.the comparative question andthe pragmatic accountThe history of epistemology has its conceptual roots inthe dialogues of Plato, and the question of the value ofknowledge and truth arises there as well. In Plato’s Meno,Socrates and Meno discuss a number of issues, includingthe issue of the nature and value of knowledge. Socratesraises the question of the value of knowledge, and Menoanswers by proposing a pragmatic theory: knowledge isvaluable because it gets us what we want. Socrates imme-diately proposes a counterexample, to the effect that trueopinion would work just as well: If you want to get toLarissa, hiring a guide who has a true opinion of how toget there will have the same practical results as hiring aguide who knows the way. Meno then voices a philosoph-ically deep perplexity, wondering aloud why knowledgeshould be more prized than true opinion and whetherthere is any difference between the two. Meno thus ques-tions two assumptions, the first being the assumptionthat knowledge is more valuable than true opinion, andthe second that knowledge is something more than trueopinion.Socrates’s counterexample suggests another: If youwant to get to Larissa, it matters not whether your guidehas true opinion or merely empirically adequate views onthe matter. To see the counterexample, we need to under-stand that an empirically adequate theory is one that“saves the appearances,” in other words, one that wouldnever be refuted by any sensory experience. The simplestway to see that such a theory is not the same thing as atrue theory is to consider skeptical scenarios such as RenéDescartes’s evil demon world. The denizens of such aworld will have roughly the same views as we do, andtheir views will be as empirically adequate as ours. Sincethe demon is so skillful at carrying out his intentions,however, their views will be false even if ours are true. Insuch a world, there are no guides with true opinionsabout how to get to Larissa. Instead, the best one couldhope for is a guide who has an empirically adequate viewof the matter. Yet, if we compare the two situations, theone in the actual world where the hired guide has a trueopinion, and the one in the demon world where the hiredguide has only an empirically adequate opinion, no suf-fering accrues to the traveler in the demon world thatdoes not also accrue to the traveler in the actual world,and no benefits are experienced by the traveler in thedemon world that are not also experienced by the travelerin the actual world. That is to say, their experiences areindistinguishable, leaving us to wonder what practicaladvantage truth has over empirical adequacy.skepticism about the value ofknowledge and truthBesides this Platonic threat to the value of knowledge andtruth, there are other threats. One arises from the specterof skepticism. If we grant that there is no adequate answerto the skeptic, we might have the experience of philo-KNOWLEDGE AND TRUTH, THE VALUE OFENCYCLOPEDIA OF PHILOSOPHY102 • 2 n d  e d i t i o neophil_K  11/2/05  3:40 PM  Page 102

Knowledge and Modality

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Knowledge and Modality

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