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The Deeper Protestant Conception of Natural Theology

It was most likely between 1888 and 1890, during his time at the Theological School in Grand Rapids, that Geerhardus Vos both delivered his Natural Theology lectures and wrote his Reformed Dogmatics. Together those works present a comprehensive doctrinal system of confessionally Reformed theology and therefore ought to be interpreted in light of one another. 

In Reformed Dogmatics, Vos incisively leverages the Reformed doctrines of the image of God, the covenant of works, and original sin against “the externalist character of Roman Catholic religion”1 that “has in principle appropriated the Pelagian conception of the will as liberum arbitrium.”2 According to Vos, the nature-grace externalism of medieval Roman Catholicism stands in sharp contrast to the “deeper Protestant conception”3 of the image of God and the “deeper conception of original sin”4 entailed by it. 

In the recently published Natural Theology, Vos rejects the “semi-Pelagianism of the Roman Catholic church”5 and identifies a cast of Roman Catholic “scholastics”6 who do not view the “human race” after the fall “as entirely corrupt.”7 He sets this semi-Pelagianism of the medieval Roman Catholic church over against “Augustine’s doctrine of human corruption” that was “revived during the Reformation.”8 He specifically highlights the classically Reformed rejection of the semi-Pelagianism imbedded in traditional Roman Catholic doctrine that sinners can “rely on their own powers for their knowledge of God”9—a view that Vos contends flows directly from a “weakened” conception of original sin.10

Reading Vos’ Natural Theology in light of Reformed Dogmatics illumines his critique of the traditional Thomistic nature-grace anthropology and the semi-Pelagianism that flows from it. Vos’ work from Reformed Dogmatics finds explicit and sweeping application in Natural Theology. Allowing the two works to interpret one another shines the spotlight from Reformed Dogmatics onto Vos’ recurring claim in Natural Theology that the Reformed explicitly rejected traditional Roman Catholic natural theology and forged in its place a distinctively Reformed alternative.

John Fesko fails to understand this central point in his “Introduction” to Vos’ Natural Theology, asserting that “Vos and Aquinas might seem like an ill-matched pair, but the two actually do belong together”11 in their approaches to natural theology. Put a bit differently, Fesko thinks that Aquinas expresses a natural theology that is congenial to Vos’ in the quest for the “retrieval of a Reformed natural theology.”12 While many might view Aquinas and Vos as “oil and water,”13 Fesko argues that such is not the case. According to Fesko, Thomas Aquinas, the Westminster Confession of Faith, and Vos fit coherently within “general patterns of patristic, medieval, and Reformation expressions, that is, in terms of God’s two books, nature and Scripture.”14 Fesko makes these claims about Aquinas and Vos, even though Vos nowhere cites Aquinas in Natural Theology. Nonetheless, Vos does offer a sweeping and penetrating critique of the medieval Roman Catholic nature-grace model of explicit Thomistic provenance. 

In what follows I will propose a reading of Vos’ Natural Theology in light of his Reformed Dogmatics that will challenge Fesko’s interpretations of Vos and Aquinas and will enable a comprehensive engagement with and critique of traditional Roman Catholic natural theology.


  1. Geerhardus Vos, Reformed Dogmatics, ed. Richard B. Gaffin Jr., trans. Richard B. Gaffin Jr., vol. 2 (Bellingham, WA: Lexham Press, 2012–2016),12. “Externalist” captures Vos’ comprehensive argument regarding the traditional Roman Catholic conception of religion. By “externalist” Vos alludes to what traditional Roman Catholic theology understands and sees as extrinsically and supernaturally added to the nature of Adam as the image of God. According to Vos, the traditional Roman Catholic conception of nature (imago) demands the ontological and ethical supplement of externally infused grace (similitudo) that enables a religious relation to God. Thus, Adam was not in his created nature in a religious relation to God and therefore needed an externally supplied infusion of grace to achieve such a religious relation. This is what Vos has in mind when he speaks of “the externalist character of Roman Catholic religion.”
  2. Ibid., 2:13. Liberum arbitrium means “liberty of the will,” which, in the Pelagian conception, holds that the will is determined neither by natural causality nor by the decree of God.
  3.  Ibid. This phrase captures Vos’ comprehensive argument regarding the “internalist” character of religion in classical Reformed theology. According to Vos, the deeper Protestant conception of the image of God yields a natural religious fellowship with God under the covenant of works with no need for a donum superadditum. This natural religious internalism of Reformed covenant theology presents a sharp contrast to Rome’s supernatural religious externalism. This contrast explains Vos’ rejection in Natural Theology of the semi-Pelagianism at the heart of the medieval Roman Catholic natural theology.
  4. Ibid., 2:14.
  5. Geerhardus Vos, Natural Theology (Grand Rapids, MI: Reformation Heritage Books, 2022), 8.
  6. Ibid.
  7. Ibid.
  8. Ibid., 10.
  9. Ibid.
  10. Vos, Reformed Dogmatics, 2:13.
  11. John Fesko, introduction to Natural Theology, (Grand Rapids, MI: Reformation Heritage Books, 2022), xvii.
  12.  Ibid.
  13.  Ibid.
  14. To substantiate this claim, Fesko speaks of “general patterns of patristic, medieval, and Reformation expressions, that is, in terms of God’s two books, nature and Scripture.” (“Introduction,” xxix). He then cites from Thomas Aquinas and alludes to the Westminster Assembly’s comments on Romans 1:19–20. His appeal to “general patterns” and citations of common texts are urged to support his initial argument that Vos and Aquinas “actually do belong together” within a general history of natural theology that affirms the two books of Scripture and nature. Fesko’s claim that a common commitment to “God’s two books, nature and Scripture” supplies continuity between the classical Reformed and traditional Roman Catholic approaches fails to appreciate at least two factors. First, the commitment to underproportioned nature that requires the supernatural grace resident in the donum unites Trent (1563), Vatican I (1870), and Vatican II (1965). Second, this explains why Vatican II’s emphasis on “experience” does not alter the fundamental teaching of traditional Roman Catholic theology regarding nature and grace. In Roman Catholic theology in all eras, Scripture, reason, tradition, and experience, as interpreted by the magisterium, carries authority. These observations, along with Vos’ own treatment of medieval Roman Catholic natural theology in Natural Theology and in Reformed Dogmatics, neutralize whatever unity Fesko might propose exists when it comes to how the Reformation and Rome interpret “God’s two books, nature and Scripture.”

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