The past twenty five years or so have not exactly been a golden age of evangelical reflection upon the Trinity. This is due in part to modern theological amnesia regarding some of the most basic elements of biblical, trinitarian reasoning (as Stephen Holmes has shown here). It is also due to the (all too often) haphazard manner in which the Trinity has been used in debates regarding gender roles in the church.
I recently read an essay by a leading evangelical theologian arguing that many “egalitarian” discussions of the doctrine of the Trinity threaten to compromise basic tenets of orthodox Christianity and to undermine, at least implicitly, the authority of the Bible (Wayne Grudem, “Doctrinal Deviations in Evangelical-Feminist Arguments about the Trinity,” in Bruce A. Ware and John Starke, eds., One God in Three Persons: Unity of Essence, Distinction of Persons, Implications for Life [Crossway, 2015], chap. 1).
Over the course of the essay, the author extensively criticized some of these approaches for subscribing to the doctrine of “inseparable operations.” The doctrine of inseparable operations teaches that, because the three persons of the Trinity are one God, each person of the Trinity is operative in all of God’s external works–from creation through redemption to consummation. More concisely stated: “the external works of the Trinity are indivisible” (opera trinitatis ad extra indivisa sunt).
Though I share the author’s complementarian commitments, as well as his concerns about the way some egalitarian theologians treat the Trinity, I believe his attempt to correct these treatments of the Trinity by denying the doctrine of inseparable operations represents a cure that is worse than the disease. To deny the doctrine of inseparable operations is to undermine classical trinitarian theology at its core.
As Lewis Ayres and others have demonstrated quite extensively over the past couple of decades, fourth century trinitarian thought, the context within which “Nicene Christianity” as we know it emerged, was characterized by three basic features: (1) a clear sense of the distinction between “person” and “nature” in the Godhead, with the understanding that there are three of the former and only one of the latter; (2) a conviction that the eternal generation of the Son does not constitute a division between the being of the Father and the being of the Son but rather that it occurs within the indivisible and incomprehensible being of God; and (3) a belief that the unity of being among the Father, the Son, and the Spirit entails a unity of operation in their works toward creatures.
These three features, we should note, not only characterize fourth century trinitarian theology; they also characterize mainstream trinitarian theology East and West, late patristic, medieval, and modern, Catholic and Protestant.
The doctrine of inseparable operations has received broad acceptance in the church because it enjoys a solid foundation in Holy Scripture. The doctrine reflects a pattern of theological reasoning that follows from a biblical pattern of divine naming.