The City of God stands as Augustine's masterwork of theological defense and construction, written over thirteen years in response to accusations that Christianity brought ruin upon Rome. This first volume contains the first ten books of sustained refutation—demolishing pagan claims that traditional worship secured either temporal prosperity or eternal happiness—followed by the beginning of his positive vision in Books Eleven through Thirteen, where he traces the origin of two societal orders to the primordial division among the angels. What emerges is not merely an apology for Christianity but a philosophy of history that subordinate the fate of empires to the hidden providence of the one true God, whose sovereignty extends from creation through the fall to the final judgment.
Augustine strengthens his case by pointing to twins of different sexes. He personally knows a brother and sister, twins now grown to adulthood, who share a family resemblance yet have pursued completely divergent paths. The brother serves as a military count, constantly abroad on campaign; the sister has never left her native region. More striking still, he is married with numerous children, while she has consecrated herself as a sacred virgin. If the stars at conception were identical for both, they failed to determine even so fundamental a characteristic as sex. Yet astrologers would have us believe that the stars at birth determine the vast difference between the married state and consecrated virginity. Augustine concedes that celestial bodies may influence certain physical phenomena—the seasons, the tides, the growth of certain creatures—but this hardly implies that human wills are subject to stellar domination. The will remains free, and the gifts of God are freely bestowed.
The practice of choosing auspicious days for marriage, planting, or conception further exposes the incoherence of astrological thinking. If the stars truly governed all outcomes, then selecting a favorable day would accomplish nothing, for the natal horoscope would already have determined the result. Yet people believe they can improve their fortunes by choosing the right moment. A learned man, according to one story, selected a specific hour to lie with his wife in hopes of begetting an illustrious son. But if he could alter his destiny through such a choice, then the stars did not fix his destiny after all. The astrologers cannot have it both ways: either the natal chart is supreme and human choice is powerless, or human choice can modify outcomes and astrology is false. Moreover, if the stars rule over all terrestrial things, then one must account for the countless multitudes of plants and animals that come into existence at the same moment yet meet vastly different ends. When a field is sown, innumerable grains germinate simultaneously, yet some are destroyed by disease, some consumed by birds, and some harvested by men. Did each grain have its own distinct constellation? The very suggestion is absurd.
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