White, M. “Pluralism and Secularism in the Political Order: St. Augustine and Theoretical Liberalism.” The University of Dayton Review, Vol. 22 (1994), pp. 137-53.  

Abstract (from FindingAugustine.org):

“White examined the nature of Augustine’s pragmatic political philosophy in light of contemporary discussions of theoretical pluralism, secularism, liberalism and church-state separation.”