Trinity

The doctrine of the Trinity provides the Christian Church with the comprehensive grammar of God and salvation. Consequently, the Trinity is not one doctrine among others in the Christian confession—and a rather difficult and speculative doctrine at that. Rather, it is an articulation of the substance of the Christian faith. The doctrine of the Trinity, in other words, secures our belief that God truthfully revealed himself in the gift the Father gave by sending his Son in the flesh and by pouring out the Holy Spirit in order to draw his wayward creatures back to himself. By confessing that God is eternally one Being in three Persons, or by confessing that the Son and the Holy Spirit “are of one substance with the Father,” we are affirming in a compressed and precise way that the God who disclosed himself in the Scriptures and the economy of salvation is the God who truly is. The attempt to articulate this doctrine well and truthfully has generated significant reflection, as well as significant conflict, over the history of the Church. The fourth century debates between the Council of Nicaea and the Council of Constantinople were especially influential in this endeavor, and the creedal summary that those debates produced—alternatively referred to as the “Nicene” or “Niceno-Constantinopolitan” Creed—have served as the orthodox standard of Trinitarian theology ever since. Candidates for ordination should be able to explain the substance and importance of the Christian doctrine of the Trinity and how the Nicene Creed gives expression to it. They should also be familiar the following terms and concepts of Trinitarian theology:

1. Consubstantial (Gk. Homoousios)

This term refers to the commonality of divine substance, which is one and identical in the Father, Son, and Holy Spirit. We confess in the Nicene Creed that the Son is “of one substance with the Father,” and later tradition follows Gregory of Nazianzus in confessing the same of the Holy Spirit. By doing so, we are expressing our belief that the Son and Spirit are fully God no less than the Father.

1. Coequality of Persons

The three persons of God are fully equal as God. There are no gradations or distinctions of nature in the Trinity.

1. Nature/Person—The distinction between divine person and nature leads us to what is most difficult to grasp in Trinitarian doctrine, namely, that God is One and Three, one in nature and three in persons. “Nature” refers to what something is, and this is common to the three persons. Each is fully God with no distinction in their nature. “Person” refers not to what a thing is but who (i.e. the individual). In Trinitarian doctrine “person” designates what is distinct and Three in God. So, while the Father, the Son, and the Holy Spirit are identical as God (nature), they are nevertheless not identical with one another (person).
2. Processions/Relations

If the three Persons of God are identical in nature, what allows us to distinguish them? The Persons’ relations of origin allow us to identify what is distinct to each divine Person, their personal properties. The Father’s distinct properties are that he alone is unbegotten and he alone begets. The Son’s distinct property is that he alone is begotten (filiated). The Holy Spirit’s distinct property is that he proceeds (is spirated, breathed forth) from the Father and the Son. To sum up, the three are distinct in God solely because of their relations of origin: the Father is unoriginated, the Son is begotten and the Spirit proceeds. In every other way, they are identical.

1. Inseparable Operation

Because the Trinity is consubstantial, the work of the Trinity is inseparable. Put simply, divine action is done by the Father, through the Son, in the Holy Spirit.

1. Immanent/Economic Trinity

The immanent Trinity is God in himself, in the eternal relations of the Father, Son and Holy Spirit. The economic Trinity is God in his Triune relation to his creatures in time, through the incarnation of the Son and the gift of the Holy Spirit. Fundamental to Trinitarian theology is the principle that who God is as Trinity is identical to who He shows himself to be in the economy of His Triune dealings with creation. This is sometimes referred to as “Rahner’s Rule,” after the Catholic theologian Karl Rahner, who said, “The economic Trinity is the immanent Trinity and vice versa.”

Recommended Reading

John of Damascus, Exposition of the Orthodox Faith . Book 1.

Thomas Aquinas, Summa Theologiae Ia.27-43.

Gerald Bray, The Doctrine of God . Contours of Christian Theology. Downers Grove, IL: InterVarsity Press, 1993.

Michael Reeves. Delighting in the Trinity: An Introduction to the Christian Faith . Downers Grove, IL: IVP Academic, 2012.

Resources for Further Study

Robert Letham, The Holy Trinity: In Scripture, History, Theology and Worship . Phillipsburg, NJ: P&R Publishing, 2004.

Khaled Anatolios. Retrieving Nicaea: The Development and Meaning of Trinitarian Doctrine . Grand Rapids: Baker Academic, 2011.

Gilles Emery, The Trinity: An Introduction to Catholic Doctrine on the Triune God . Thomistic Ressourcement. Washington, DC: CUA Press, 2011.

Matthew Levering and Gilles Emery, eds., The Oxford Handbook of the Trinity . Oxford, UK: Oxford University Press, 2014.