Condition 3: An Externalist Condition Requiring Relevant Premises
The addition of externalist condition 3 as a necessary condition for 'S knows p' to be true
is what gives this
theory the name the 'predominately externalist' definition of knowledge.
It is stated that whether a person has knowledge,
is in significant part, contingent upon one's external material environment.
Traditionally it was thought that a person's having
knowledge is something completely internal to a cognizer's accessible perceptions, beliefs,
background beliefs,
menory, reasoning, and epistemic responsibility in assessing available evidence.
More recent externalist theories
of knowledge, in contrast, believe that a person's having knowledge is crucially a function of
external facts that a cognizer may (or may not) have access to.
Condition 3 requires that S's reasons for believing p must be 'relevant' (i.e., truth-connecting,
pertinent, or applicable) for why p is true. The evidence that is
actually relevant for why p should be believed true, is
presumed objective and independent of persons.
Condition 3 makes no normative (nor contextual) claim about how much relevant evidence is 'adequate' or
'sufficient' to believe p, and doesn't imply that S needs to be conscious of (or be able to recount) the
reasons for believing p, except in situations of critical doubt.
Condition 3 can be compared to, and is an alternative to other externalist relations that have been suggested such as causation,
subjunctive tracking, or reliable belief formation.
This condition is similar to reliabilism in
that it is an externalist condition, but it makes no reference to reliable processes.
Process reliabilism states that a belief is justified if and only if the belief is the result of a
'reliable belief forming process.' A belief forming process is reliable if and only if it (in fact)
yields a high proportion of true beliefs in a large and varied run of experiences that we usually encounter.
Condition 3 is stronger. As a condition for knowledge, it asserts that a justified belief is a function of
premises that are truth-connecting for why p should be believed and not just premises (or reliable mechanisms)
that are truth-conducive for why p should be believed.
Condition 3 doesn't imply that all of S's premises for believing p must be true and relevant.
Suppose Mary has strong evidence for p:
'Some people in my work place own a Ford truck.'
Mary's evidence (e1 to e5) for believing p is that five persons at
her work place own Ford trucks:
Tom owns a Ford truck,
Jennifer owns a Ford truck,
Fred owns a Ford truck,
Ken owns a Ford truck, and
Carol owns a Ford truck.
All of these persons are long-time Ford
truck owners, and she saw two of these co-workers park Ford trucks in the company parking lot this morning. But,
unknown to Mary, one of the five workers sold his truck yesterday, and presently owns no vehicle.
Does Mary still
know that some people in her work place own Ford trucks? Does one false evidential premise make it false that Mary
knows p? Intuitively, we would maintain that Mary still knows p. In order for condition 3 to be satisfied,
Mary's evidence can consist of true (and relevant) premises for why p should be believed without requiring that every
single piece of evidence be true or relevant for why p should be believed.
It should be noted that even if four out
of five premises are false, condition 3 would still be satisfied because Mary would still possess objectively (weak)
relevant evidence for the weak claim that 'some people in my work place own a Ford truck.' But, if Mary continued
to believe this true p, even though only one of her five premises were true, we may be inclined to say that Mary no
longer knows p, based upon a violation of condition 4b.
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