Antithetical Cities?

Question:

Back in chapter 1: City on a Hill, Darryl wrote, “But as antithetical as the two cities were in Augustine’s mind, and as much as that antagonism might seperate believers from nonbelievers… (pg. 39).

I am confused by this reading of Augustine. In this age, can the two cities be understood as really antithetical? In one sense it is certainly true but are these cities not confounded and mixed together in a way that cannot be seperated in this age? Are we to understand Augustine’s metaphor in the simplistic division between church and state?

Copelston writes: “the ideas of the heavenly and earthly cities are moral and spiritual ideas, the contents of which are not exactly coterminus with any actual organization. For instance, a man may be a Christian and belong to the Church; but if the principle of his conduct is self-love and not love of God, he belongs spiritually and morally to the City of Babylon. Again, if an official of the State is governed in his conduct by the love of God, if he pursues justice and charity, he belongs spiritually and morally to the City of Jerusalem. ‘We see now a citizen of Jerusalem, a citizen of the kingdom of heaven, holding some office upon earth; as, for example, wearing the purple, serving as magistrate, as aedile, as proconsul, as emperor, directing the earthly republic, but he hath his heart above if he is a Christian, if he is faithful…’” (History of Philosophy, Vol. 2, pg. 103, citing Augustine, In Ps., 51,6).