Simplifying to the extreme, I define postmodern as incredulity toward metanarratives.
Incredulity is the wisdom of the fool.
Incredulity is not wisdom.
...the incredulity of mankind, who do not truly believe in anything new until they have had actual experience of it.
Nothing is so contemptible as that affectation of wisdom, which some display, by universal incredulity.
Knowledge of divine things for the most part, as Heraclitus says, is lost to us by incredulity.