In Rome, scholars like Varro recognized three predominant theologies. Genus mythicum, or that of the poets, which irritated Plato enough to vanish their lot. Genus physicum, or the theology of the philosophers such as Plato and Aristotle. And finally the Genus Civilis(by the way, I am going by Arnaldo Momigliano’s article on Roma Religion), the religion of the multitude, of the empire, that had to be maintained because Rome owed it’s strenght to it. It did not matter if the religion could pass the muster of reason, because religion in these times was a practical matter, not a purely theoretical one.
That all said, here is my speculation.
The three really boil down to two, the poet and the people. It was originally the poet (the shamman) that gave something to the people. The role of the poet is theoretical. He sets the formula up. The people role’s is practical. They put into practice the formula. The role of the philosopher is actually the link that closes the circle. He is part people and part poet. When the original formula begins to lose explanatory powers (perhaps because of change of conditions, such as loss of political hegemony), the philosopher, who is part of the people, that is, comes from an established culture and a particular religious formula, begins to highlight the explanatory shortcomings, and sometimes to offer new formulas (as Plato and Nietzsche). Even when their critique is purely negative and prescrive nothing, apparently, in reality they are washing the slate clean for the introduction of something else. Even if Cicero’s work was negative his work was positive in his attempt to remove superstition from religion.
He did not succed, nor could anyone, because it is a primal instinct of ours to find patterns in phenomena.
But his work left the slate clean for the new religions to fill the vacuum, and so the philosopher, this sceptic, opened the door for new poets to give new myths to the people, new formulas to be tried and tested. The poets use the philosopher’s work, if nothing else, to polish their new formulas and correct the deficiencies of the previous formulas, sometimes in an effort to simply reinterpret elements that seem still important from the old religion and other times as a new revelation altogether.
So it goes from poet to people to philosopher and then back to poet. The philosopher’s God is always too empty, to abstract to serve the needs of the people. That is why philosopher’s are more effective at bringing down idols than at setting a replacement…even when they try they still need the help of a poet to vulgarize their high abstractions enough to be popular as religion. Otherwise they remain the interesting muse of eccentrics and mystics.