Oliver O’Donovan lays out an extremely helpful overview of the structure of City of God 19, which includes an explanation of why Augustine must wait until book 19 to return to themes discussed in book 2. As he observes, Augustine used the “space” to develop and to make clear his distinction between true, perfect peace attainable only in eschatological fulfillment and earthly, imperfect peace attainable in part in the present age. More specifically, O’Donovan contends that from the start, it was Augustine’s intention “to develop his discussion of the social coherence of the two cities around their respective ideas of peace into thoughts on the status of the earthly commonwealth.” Regarding the imperfect earthly peace, Augustine instructs the “pilgrims” of the “Heavenly City” living in this world not to destroy the particular “customs, laws, and institutions by which earthly peace is achieved or maintained,” but to uphold these so long as they do not hinder the Christian’s ability to worship God. In fact, Augustine acknowledges, and by implication affirms, the Heavenly City’s employment of “earthly peace” and the co-laboring with likeminded others “in the attaining of those things which belong to the mortal nature of man.” Once again, the only caveat given is that these joint efforts and common pursuits do not harm the pilgrim’s pursuit of “true godliness and religion.” Whether we have in view Augustine’s political setting or our own, this striving toward “earthly peace” involves working together with like-minded others (both inside and outside the Christian tradition) to promote human flourishing. In a contemporary setting, such shared activity might include deliberating about current and future legislation on important issues such as healthcare, education, racial profiling, affirmative action, child welfare, incarceration, social assistance programs for the poor, underprivileged, and undereducated, and so forth. Augustine’s own affirmation of the value of those “customs, laws, and institutions by which earthly peace is achieved or maintained” suggests that he also recognizes that non-Christian others possess intellectual and moral virtues and have something worthwhile to contribute to the public good.
O’Donovan continues his analysis and cautions against overemphasizing idealist and realist interpretations of Augustine. The former tend to place too much stress on the Augustinian impulse regarding the impossibility of a perfectly just society in this world. The latter tend to accent the Augustinian impulse regarding the possibility of cooperation between the two cities constituted by different and competing ultimate loves. When either position is pushed to its extreme, O’Donovan argues, Augustine is misrepresented. My own impulse desires a third way, comprised of elements of both views and which upholds, as Eric Gregory puts it, “the dialectical relation between love and sin.” That is, even if Augustine does not advocate for a purely “neutral” public square, I see no reason why a contemporary Augustinian could not appeal to areas of ethical and socio-political overlap between those whose hold different and even conflicting comprehensive views of the world and humanity. For example, both the secular humanist and the Christian may share common views about a civic right to marry, universal human rights, and the need to protect exploited and marginalized groups. Even if their ultimate, rock-bottom reasons for their views are motivated differently, nonetheless, they can and do work together in common pursuits advancing human flourishing and freedom.
 See, Oliver O’Donovan, “The Political Thought of City of God,” in Bonds of Imperfection: Christian Politics Past and Present, (Grand Rapids: Eerdmans, 2004): pp. 48–72, esp. pp. 52-9.
 Ibid., p. 54.
 Augustine, City of God, pp. 946–47 [De civ. Dei,19.17].
 Ibid., p. 947 [De civ. Dei,19.17].
 Oliver O’Donovan, “The Political Thought of City of God,” 55–6.
 Gregory, Politics and the Order of Love, p. 21. See also, James Wetzel, “Splendid Vices and Secular Virtues: Variations on Milbank’s Augustine,” Journal of Religious Ethics 32 (2004): pp. 271–300. I resonate with Wetzel’s aim, “to transform a dramatic choice—pagan or Christian—into a common hope for better wisdom” (ibid., p. 283).
 John Duns Scotus, an heir of the Augustinian tradition, continues and develops this Augustinian motif. That is, Scotus articulates a robust, multidimensional view of freedom, which not only promotes human flourishing but also condemns oppressive practices that hinder one’s ability to develop one’s moral and intellectual capacities. In particular, in Ordinatio IV.36.1 Scotus argues that slavery as described by Aristotle in book I of the Politics is incompatible with natural law (see Wolter, Will and Morality, 325; Scotus, Ord. IV, d. 36, q. 1. [Wolter’s translation is based on his transcription of the authoritative Codex A; the critical edition for this text is not yet available]. Scotus’s position is not without its problems—particularly his statements toward the end of the article in which he affirms the status quo based his interpretation of certain biblical texts—nonetheless, it is a Christian position within the Augustinian line voicing clear moral and intellectual dissatisfaction with its own tradition’s, as well as previously held (Aristotle et al.) dominant discourses on slavery.