Many Reformed theologians acknowledged the virtue of pagans and their ability to know the natural law as it relates to human social relations—even to the point of acknowledging a sort of natural sociability. Reformed theologians “have always fully acknowledged,” writes Dutch Reformed theologian Herman Bavinck,
the existence and moral value of [the virtue of pagans.] Since after the fall people have remained human and continue to share in the blessings of God’s common grace, they can inwardly possess many virtues and outwardly do many good deeds that, viewed through human eyes and measured by human standards, are greatly to be appreciated and of great value for human life. But this is not to say that they are good in the eyes of God and correspond to the full spiritual sense of his holy law.
Calvin affirms a distinction between “earthly” objects (“matters of policy and economy, all mechanical arts, and liberal studies”) and “heavenly” objects (“true righteousness and future blessedness”), and when man is focused on the former he can achieve “some result,” proving that “some principle of civil order is impressed on all. And this is ample proof that…no man is devoid of the light of reason.” Though man “lost all understanding” on matters related to heaven, not all was lost on earthly matters. Man can still be “very acute and sagacious” on earthly matters, but not on heavenly matters. Man’s “supernatural” virtues—those which relate to heaven and the eschaton, such as “the light of faith and righteousness”—were “withdrawn,” but the natural gifts were only “corrupted,” ensuring that there is still “civil order impressed on all.”
Hence, within the Reformed framework there is potential great optimism concerning man’s ability to reach sound conclusions on natural duties. This is why the Reformed political theorist, Johannes Althusius can consistently state, “But in political life even an infidel may be called just, innocent, and upright.” Turretin argues for the existence of the natural law by citing the “consent of the nations, among whom…”
some law of the primitive nations obtains, from which even without a teacher they have learned that God should be worshipped, parents honored, a virtuous life be led and from which as a fountain have flowed so many laws concerning equity and virtue enacted by heathen legislators, drawn from nature itself. And if certain laws are found among some repugnant to these principles, they were even with reluctance received and observed by a few, at length abrogated by contrary laws, and have fallen into desuetude.
More evidence and analysis to come…
 Herman Bavinck, Reformed Dogmatics: Holy Spirit, Church and New Creation Translated by John Vriend (Grand Rapids: Baker Academic, 2008), 256-7.
 Calvin, Institutes, 2.2.13.
 Calvin, Commentary on the Book of Isaiah 44:18.
 See Calvin, Institutes, 2.2.13.
 Calvin, Commentary on the Book of Isaiah, 44:18.
 See Calvin, Institutes, 2.2.12, 13.
 Johannes Althusius, Politica: An Abridged Translation of Politics Methodically Set Forth and Illustrated with Sacred and Profane Examples, ed. and Trans. Frederick S. Carney (Indianapolis: Liberty Fund, 1964), 147. The Canons of Dordt (1619), a major statement of Reformed theology, states that fallen man “shows some regard for virtue and for good outward behavior” (3/4.4).
 Turretin, 11.1.13. Emphasis mine.