30 Mark Perlman
D6 S knows that h iff (i) h is true, (ii) S is justifi ed in believing that h (that is, there is a true body
of evidence e such that S is justifi ed in believing e and e justifi ed h), (iii) S believes that h on the
basis of his justifi cation and (iv) S’s justifi cation for h is indefeasible (that is, it is not logically pos-
sible that there is a body of evidence e’ such that the conjunction of e and e’ fails to justify h).
This is followed by various revisions of clause (iv) culminating in the following:
(ivg) S’s justifi cation for h is indefeasible (that is, there is an evidence-restricted alternative Fs
to S’s epistemic framework Fs such that (i) “S is justifi ed in believing that h” is epistemically deriv-
able from the other members of the evidence component of Fs and (ii) there is some subset of
members of the evidence component of Fs* such that (a) the members of this subset are also
members of the evidence component of Fs and (b) “S is justifi ed in believing that h” is epistemically
derivable from the members of this subset).
I quote this defi nition at length as a warning—let us resist the urge to produce similarly
out-of-control overblown defi nitions for teleological functions. Yet that is exactly the
direction we have been headed since 1984.
This is especially ironic because Wright’s infl uential 1973 paper on functions was a
huge step in simplifying the philosophical defi nitions of functions. In the 1950s and 60s,
the Deductive-Nomological model of explanation was still dominant, and highly complex
defi nitions of function from Hempel (1959), Beckner (1959), Nagel (1961), and Canfi eld
(1966) were just what Wright was reacting against in devising his elegant and concise
view of function. The point is not that complexity is bad in itself or that explanations are
never complicated. But the basic principles of nature do indeed tend to be simple (i.e.,
E = mc^2 ), though they are instantiated in complex ways. Thus one could hope that a
few simple notions of function should be the basis for multifaceted explanations of
phenomena.
To continue our brief tour through epistemology, what emerged were three competing
approaches—Foundationalism, Coherentism, and Reliabilism.^7 (Reliabilism is related to
the additional camp known as Naturalized Epistemology, which seeks to step out from
armchair theorizing and base epistemology on empirical results in cognitive science.) For
some period these three big camps battled it out over the correct approach to the defi nition
of knowledge and the nature of justifi cation. Then in the late 1980s, the smoke cleared,
and people stopped worrying about the Gettier problem, and the three camps quieted the
battles. It wasn’t that the Gettier problem had been solved but rather that people recognized
that it was not productive to continue to make it the central focus of epistemology. More-
over, it began to look as if each of these three big camps of Anglo-American epistemology
had something to offer, and perhaps they might be arguing past one another. Many phi-
losophers began to think that defi ning the necessary and suffi cient conditions as to when
S knows that p isn’t so vital after all, and shouldn’t be the exclusive focus of epistemology.
More important are the conditions of justifi cation. Even there, it seems to have become
clear that there are simply different senses of justifi cation, and each has a role to play in