Postmodernism made some valid critiques of modern epistemology but also went too far in some ways: 1) It changed the modal ontology from "possible, actual, and probable" to "possible, actual, and whatever," opening an undecidable epistemic category of "huh?" 2) While undecidability is a valid concept, postmodernism erred in betting all its chips on inconsistency rather than consistency. 3) Postmodernism properly challenged theories of knowledge but wrongly challenged the concept of truth itself without valid logical arguments.

1. In a rather predictable way, there have always been persons
and even peoples at early stages of development (intellectual,
moral, aesthetic, social and/or religious) who have perverted
the meanings of humankind's latest authentic insights,
inevitably twisting them to their transparently selfish (and
puerile) ends of either avoiding pain (and fear) or pursuing
pleasure (and security), above all other goals (otherwise,
there's nothing intrinsically unworthy about those ends). To
wit: Science sometimes devolves into scientism, faith into
fideism, philosophy into rationalism, culture into
provincialism, ritual into ritualism, law into legalism, dogma
into dogmatism, common sense realism into fundamentalism(s)
and the postmodern critique into postmodernism.
What the critique had suggested is that the categories of our
modal ontology be changed from 'possible, actual & necessary'
to 'possible, actual & probable' and that our corresponding
epistemic categories reflect a new semantical vagueness where
such first principles as noncontradiction [NC] & excluded
middle [EM] alternately hold or fold for each of those
categories: possible [NC folds, EM holds], actual [NC & EM
hold] and probable [NC holds, EM folds].
What postmodernism did is to change our modal ontology to
'possible, actual and whatever' and, in doing so, broke open a
new epistemic category: 'huh?' [undecidability]. Now,
undecidability is a valid working concept, proven, in fact, by
Godel's incompleteness theorems, which tell us that we can
have either consistency or completeness but not both. But, as
even Stephen Hawking would later come to believe and point out
- the good money's always been placed on consistency, while
abiding with incompleteness. That is to say that postmodernism
erred in betting all its chips on inconsistency, as if that
were the 'complete ' non-answer.
The postmodern critique properly (& hygienically) challenged
our theory of knowledge, leaving our theory of truth
untouched. Postmodernism challenged truth, itself, but only
for all practical purposes, for there is no challenge to truth
on theoretical grounds, employing logical arguments. However,
while there is no logical adjudication of these alternate
approaches, the normative sciences have always had other tools
at their disposal, measures such as the practical and the
absurd.
http://www.independent.co.uk/arts-
entertainment/art/features/pomo-everybodys-doing-it-
2353050.html
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