When we say that God is “triune42,” we mean that He is three-in-one (not three and one, at least not in the same respect). In terms of person, God is three: Father, Son, and Spirit. In terms of essence, God is one. To say that God is triune, then, is to say that the one God exists in three persons. “The tri-unity of God means that the divine essence subsists wholly and indivisibly, simultaneously and eternally, in Father, Son, and Holy Spirit” (Rolland McCune, “Systematic Theology I” class notes, p. 126). All three persons of the Godhead are coequal, coeternal, coinherent (John 10:38), and consubstantial (of the same substance). They are “distinguishable as persons, but one and inseparable in their being” (Millard Erickson, Christian Theology, p. 337). The persons must not be confounded, nor must the essence be divided. The Godhead exists undivided in divided persons.
The Triunity of God in Scripture Though the triunity of God is not treated in a full and formal sense in any one passage in Scripture, it can be inferred from numerous passages in both testaments, more clearly so from texts in the New Testament.
The Triunity of God in the OT
Texts in the OT that speak of God in terms of plurality43:
Then God said, “Let Us make man in Our image, according to Our likeness . . . .” (Gen 1:26)
Then the LORD God said, “Behold, the man has become like one of Us, knowing good and evil . . . .” (Gen 3:22)
“The LORD said, “ . . . Come, let Us go down and there confuse their language . . . .”(Gen 11:7)
Then I heard the voice of the Lord, saying, “Whom shall I send, and who will go for Us?”(Isa 6:8a)
• Texts in the OT that mention both the Father and the Son in distinction from one another: Psalm 2:7 (cf. Acts 13:33, Heb 1:5, 5:5), 45:6-7 (cf. Heb 1:8-9), 110:1 (cf. Heb 1:13), Proverbs 30:4
Texts in the OT that mention Father, Son, and Spirit in distinction from one another: Isaiah 48:16, 61:1 (cf. Luke 4:16-21)
The Triunity of God in the NT
• Texts in the NT that mention Father, Son, and Spirit in distinction from one another: Matthew 3:16-17, 28:19, John 14:16-17, 26, 15:26, 1 Corinthians 12:4-6, 2 Corinthians 13:14, Ephesians 4:4-6, 1 Peter 1:2, and Jude 20-21
Note: 1 John 5:7 (in the KJV), containing the infamous “Johannine Comma,” is not included in the above list because of its likely spurious origin.
The Triunity of God in Church History According to John Feinberg (No One Like Him, p. 473), it was Tertullian (A.D. 160-225) who first coined the term “trinity.”44 Two famous church councils in particular addressed the issue:
The Council of Nicea (325 A.D.)
The two antagonists at the Council of Nicea were Arius45 and Athanasius46. Arius taught the heresy that both God the Son and God the Spirit were created beings (the Son being created by the Father47, and the Spirit being created by the Son), while Athanasius argued otherwise. The Council of Nicea focused particularly on the Son’s relationship to the Father (the Council of Constantinople focused on the Spirit’s relationship to the Father). Followers of Athanasius contended that the Son was of the same substance as the Father (homoousios), followers of Arius contended that the Son was of a different substance than the Father (heteroousios), while others, led by Eusebius of Caesarea, pushed for a mediating position, that the Son was of a similar substance as the Father (homoiousios).48 The Council affirmed the position of Athanasius, stating that the Son was “of one substance (homoousion) with the Father.”
The Council of Constantinople (381 A.D.)
Because the focus of the Council of Nicea was on the relationship of the Son to the Father, it did not comment on the relationship of the Spirit to the Father. Therefore, the Council of Constantinople addressed this issue, affirming that the Spirit, like the Son, was of the same substance as the Father. Thus, in 381 A.D., the church officially espoused belief in the doctrine of the triunity of God.
Another interesting development in church history pertaining to the doctrine of the triunity of God involved the “filioque” controversy. The Council of Constantinople had declared that the Spirit proceeded from the Father (John 15:26).49 In 589 A.D., the Council of Toledo added that the Spirit had proceeded from the Son as well (“filioque” is Latin for “and from the Son”). The Western church agreed, while the Eastern church disagreed, a precipitating factor in the eventual Eastern-Western split of 1054 A.D.
Ontological vs. Economic When studying the triunity of God, one crucial distinction must always be kept in mind, the distinction between what has been called the “ontological trinity” and what has been called the “economic trinity.”
The Ontological Trinity
In terms of essence, being, or nature (who They are), all three Persons of the Godhead stand on equal footing (see, for example, John 10:30). All three are fully and equally God. The Son is God (Isa 9:6, John 1:1, Col 2:9, Titus 2:13, Heb 1:3, 8, 2 Pet 1:1, 1 John 5:20). The Spirit is God (2 Cor 3:17; also compare Acts 5:3 with Acts 5:4). As if to communicate this equality of essence, the three are listed in various orders in Scripture: Father, Son, Spirit (Matt 28:19); Father, Spirit, Son (1 Pet 1:2); Son, Father, Spirit (2 Cor 13:14); Spirit, Father, Son (Jude 20-21); and Spirit, Son, Father (1 Cor 12:4-6, Eph 4:4-6).
The Economic Trinity
In terms of function (what They do), the Son (John 14:28 and 1 Cor 11:3) and the Spirit (John 14:26) are subordinate to the Father, and the Spirit is subordinate also to the Son (John 15:26, Rom 8:9, Gal 4:6). Wayne Grudem (Systematic Theology, p. 257) likens the Father to a husband, the Son to a wife, and the Spirit to a child (all three are equal in essence, but unequal in function). The interrelationship of the roles performed by the Persons of the Godhead has been likened (by Rolland McCune) to those performed by an architect (the Father), builder (the Son), and construction worker (the Spirit).50 The Father is the source (from the Father), the Son the channel (through the Son), the Spirit the applicator (by the Spirit). See 1 Corinthians 8:6 and Ephesians 2:18 in the NIV in this regard. The Father purposes, the Son secures, and the Spirit applies (J. I. Packer, Knowing God, p. 20).
“Try to explain it [the doctrine of the triunity of God], and you’ll lose your mind; But try to deny it, and you’ll lose your soul.”
(source unknown, quoted in C. Samuel Storms, The Grandeur of God, p. 56)