Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!husc6!rutgers!lll-lcc!pyramid!thirdi!sarge From: sarge@thirdi.UUCP (Sarge Gerbode) Newsgroups: sci.philosophy.tech Subject: Justified true belief Message-ID: <90@thirdi.UUCP> Date: Wed, 12-Aug-87 02:02:10 EDT Article-I.D.: thirdi.90 Posted: Wed Aug 12 02:02:10 1987 Date-Received: Fri, 14-Aug-87 04:20:45 EDT Reply-To: sarge@thirdi.UUCP (Sarge Gerbode) Distribution: world Organization: Institute for Research in Metapsychology Lines: 56 Keywords: knowledge belief truth Summary: It isn't knowledge Awhile back, when we were discussing knowledge and belief, a couple of people, as I recall, suggested that knowledge was justified true belief. Since then, I have spoken to a philosopher friend, who pointed out that this criterion doesn't hold water, so I thought I'd share his thought with you. The first example is paraphrased from an article by Edmund C. Gettier called "Is justified true belief knowledge?": Consider the case where Smith has good reason for thinking that Jones owns a Ford. Imagine further that Smith has another friend, Brown, whose whereabouts he doesn't know. In this case, Smith has justified belief for: 1. Either Jones owns a Ford or Brown is in Boston. 2. Either Jones owns a Ford or Brown is in Barcelona 3. Either Jones owns a Ford or Brown is in Brest-Litovsk Each of these disjunctions is entailed by "Jones owns a Ford", for which Smith, *ex hypothesi* has justified belief. Now, suppose that Jones in fact doesn't own a Ford but is driving a rented car, and suppose further that Brown just happens to be in Barcelona. Smith then has justified true belief that "Either Jones owns a Ford or Brown is in Barcelona", but would we say that he *knows* this? A second counter-example is a causal one (not from the same article). Suppose a certain pyromaniac has a box of "Shur-Fire" matches and that he has very good reason for believing that if he strikes a match it will light. Say he strikes a match and it does, in fact, light, but it's actually a defective match and would not have lit except that a burst of "Q-radiation" came in from the stratosphere and hit it just as he scratched it across the box (or suppose an improbable concentration of high-energy molecules just happened to congregate in a certain location on the match, causing it to light). He had justified true belief that it would light, but did he *know* it would light? Each of these examples uses a chain of inferences (logical or causal) in which a term earlier than the final one in the chain is one for which a person has justified belief but which is not in fact true, and an ultimate term that happens to be true and deducible from, or could be caused by, the term that is false. In order to avoid this problem, it seems that one would have to add another proviso to the "justified true belief" criterion, namely that one would require justified true belief also in each of the non-ultimate terms in a causal or explanatory chain. A possible difficulty with this formulation is that the notion of where an explanatory chain or a causal chain *starts* is somewhat up in the air, to say the least. So you would have a lot of work showing that you had justified true belief for anything all the way back to the beginning of the chain. So you would have trouble, using this criterion, saying that you know anything. -- "Absolute knowledge means never having to change your mind." Sarge Gerbode Institute for Research in Metapsychology 950 Guinda St. Palo Alto, CA 94301 UUCP: pyramid!thirdi!sarge