Augustine on hedonism

"It is the decided opinion of all who use their brains, that all men desire to be happy" (City of God p303)

I'm not quite sure how Augustine escaped being quoted in John Piper's Desiring God: Meditations of a Christian Hedonist. In any case, I would say that the human pursuit of felicity (happiness) is the central thread that runs through the first nine books of the City of God. Indeed, the major claim I have seen thus far is this: God alone is able to give eternal happiness. The founders of Rome sought it through virtue, and their successors through the worship of the gods. Yet neither virtue nor worship of the gods offered hope of eternal felicity. This the one true God alone can give.

Why does it matter that Augustine made so much of the human desire to be happy? Augustine got this perspective from the Scriptures, and brought it to bear on his adversaries. He recognized the pursuit of happiness as the common ground through which he could proclaim the ability of Christ alone to grant that which they sought. He has already taught me much about evangelistic engagement.