"Simplifying to the extreme, I define postmodern as incredulity toward metanarratives. This incredulity is undoubtedly a product of progress in the sciences: but that progress in turn presupposes it. To the obsolescence of the metanarrative apparatus of legitimation corresponds, most notably, the crisis of metaphysical philosophy and of the university institution which in the past relied on it. The narrative function is losing its functors, its great hero, its great dangers, its great voyages, its great goal. It is being dispersed in clouds of narrative language elements--narrative, but also denotative, prescriptive, descriptive, and so on. ... Where, after the metanarratives, can legitimacy reside?" (-- Jean-Francois Lyotard)
A "metanarrative" is a grand narrative, or a singular, overarching plan over history. Or, ultimate purpose to all of history. Postmodernism likes narratives, but rejects any such transcendent narrative.
But when you've removed a Creator, moral absolutes, transcendent authority, or ultimate meaning to history, upon what do you build? What meaning or purpose is there to education, other than to become technicians without a conscience? Jesus answers...
"Everyone then who hears these words of mine and does them will be like a wise man who built his house on the rock. And the rain fell, and the floods came, and the winds blew and beat on that house, but it did not fall, because it had been founded on the rock. And everyone who hears these words of mine and does not do them will be like a foolish man who built his house on the sand. And the rain fell, and the floods came, and the winds blew and beat against that house, and it fell, and great was the fall of it." And when Jesus finished these sayings, the crowds were astonished at his teaching, for he was teaching them as one who had authority, and not as their scribes." (Matthew 7:24-29 ESV)
And finally, who does the postmodern person give thanks to on Thanksgiving? He or she may feel thankful, and perhaps give thanks to others for good circumstances provided by them. But not in any ultimate sense, since most of our blessings are beyond our control, and actually beyond the control of others. So, do you thank "time, chance and matter"?
I give thanks to God for all things good, and for all things which work for good through Jesus Christ. He alone is the true God.