Augustine here introduces Marcus Varro, an author contemporary with Cicero (i.e. ~1st century BC) who wrote much about the Roman religion, apparently not believing it himself but preserving it nonetheless as a valuable tradition. Augustine specifically seems to think he feared the popular response should they find that he had denied their gods. Which leads Augustine to praise his education but condemn his devotion to the truth and highlight Varro himself as an example of fallen human nature, even as Augustine uses his writings to advance the Gospel:
What ought we to think but that a most acute and learned man,—not, however made free by the Holy Spirit,—was overpowered by the custom and laws of his state, and, not being able to be silent about those things by which he was influenced, spoke of them under pretence of commending religion?Chapter 3-4:
Augustine first gives an outline of Varro's writings on traditional pagan religion (VI.3) and then discusses what we learn from such an outline (VI.4). Namely, that Varro places 'human things' and the state first, and only then deals with 'divine things' and the theology of the gods, even at times explicitly saying that humanity comes first and then shapes the gods to fit its own ends. As a result, from the lips of the most learned of pagans we see that there can be no possible hope of eternal life from worldly religion.