🚀 go-pugleaf

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