Augustine’s view of culture and the temporal destiny of civilizations

In his book The Micah Mandate, George Grant wrote:

“According to Augustine, culture is not a reflection of a people’s race, ethnicity, folklore, politics, language, or heritage. Rather, it is an outworking of a people’s creed. In other words, culture is the temporal manifestation of a people’s faith. If a culture begins to change, it is not because of fads, fashions, or the passing of time; it is because of a shift in worldview — it is because of a change of faith. …

“The reason he spent so much of his life and ministry critiquiting the pagan philosophies of the world and exposing the aberrant theologies of the church was that Augustine understood only too well that those things matter not only in the realm of eternity determining the spiritual destiny of masses of humanity, but in the realm of the here and now determining the temporal destiny of whole civilizations.” (emphasis added)

I would guess that Grant presupposes that the “outworking of a people’s creed” would happen within the ethnicity, language, heritage, etc., that are common to a particular people group. What Grant seems to be saying is various “fads and fashions” (media and symbols and expressions) are not the ends within themselves, but an expression of profound, basic assumptions about the universe, its origin, and what it means to be human.