How can we accept the Trinitarian faith if the God’s divine nature is simple? Does Trinitarian faith contradict divine unitary simplicity?

Some accuse Christianity of lacking simplicity; in other words, they accuse it of complexity because it believes in three Hypostases in one divine essence. They see this doctrine as liable to being interpreted as a kind of polytheism, and so claim that it is unnecessary. However, we note that most religions that reject this doctrine and believe in one absolute God do themselves believe in many divine mysteries that the mind cannot comprehend. They speak of God’s hands, face, throne, etc., despite their common belief that God is a simple Spirit with no body and therefore incapable of physically resting on a throne. Further, they accept these expressions and consider them to be mysteries although their use is liable to misinterpretation. In the same vein, we say that our faith in the Holy Trinity is a mystery revealed by God Himself to humanity. Only through divine grace can the human mind comprehend it and recognize that it confirms the oneness of God and makes sense of it.

Trinitarian faith in no way no way contradicts divine simplicity; on the contrary, to deny this faith is to distort divine simplicity, for the following reasons:

Many religions believe that the word of God is eternal, for God cannot exist without His Word, even before time began (John 1:1). Indeed, some religions even hold that the very words and letters that comprise the word of God are themselves eternal. Without the doctrine of the Holy Trinity in one divine essence, the eternity of the words of God and His sayings would mean that God’s nature is not simple, since He must be eternally united with His words. But according to our faith, the Word of God is not “external” to God; it is His eternal Word, born of Him as light is born of light, existing with Him in the selfsame essence. That is, the Word is one with the Father in divine essence ( ousia ).

Many non-Christians believe that the word of God is co-eternal with Him; that it is revealed to the prophets as a sign of God’s love for humanity; and that this word does not conflict with divine simplicity. We say that the Word “the Logos” is not outside God, but is one with Him eternally. God is not like a human being; He is an eternal being, and therefore,

His Word “the Logos” co-exists eternally with the Father, like a ray of light. St. Athanasius the Apostolic says, “But God’s Word is one and the same, and, as it is written, ‘The Word of God endures for ever’ (Ps. 119:89), not changed, not before or after other, but existing the same always.”³⁶¹

Trinitarian faith does not contradict divine simplicity for we believe not in three divine essences, but in one divine essence. To help make sense of this divine mystery, we can say that the divine essence has truly existed from eternity. This is an existence that is rational and eternal; that is, existence characterized by mind , or wisdom , or Logos emanating from its own being rather than being external to it; having no independent divine essence. Therefore, when we call the divine being “Father,” and we call the Word “Son,” we affirm that the Son is the Word of God, so that no one can misuse the two titles, as if the Father and the Son have two separate essences or think that we believe in two distinct gods; for we believe in One God. Divine simplicity cannot mean the existence of God without His Word or His mind or His wisdom. How could God exist without His mind!

On this topic, Athenagoras ,³⁶² the dean of the School of Alexandria, says that the eternal God has a mind ( logikos ), the Logos, existing in Him eternal; so the Son as the Logos did not come into existence but is co-eternal with the Father.

This divine being, “the Father,” is an eternal being. Life proceeds from Him; it is not something independent of Him. While His “being” is distinct from His “life,” they are not independent of each other, nor do they have two distinct divine essences, because “life” is specific to being itself. St. Dionysius of Alexandria says that it is necessary to believe in the living, rational divine Being; one essence, simple and eternal, because the Trinity is inseparable and none existed before the others. They are like fire that has flames, light, and heat at the same time. “Thus then we extend the Monad indivisibly into the Triad, and conversely gather together the Triad without diminution into the Monad.”³⁶³

God is unique in every respect. Even when the Bible speaks of Him as the “One God,” this does not mean He is subject to mathematical rules, for He cannot be limited like that. In other words, we need to understand the word “one” here is not a number among other numbers but means an unutterable “monad.” We cannot seek to understand this oneness or think of it as a kind of counting; that would be to make God a kind of material being who can be confined within a number. Hence, Athenagoras³⁶⁴ says that God is one, but not in the way that a human being is an individual; created, mortal, composite, and divisible (into parts). God is neither born nor variable nor divisible; He is not composed of parts. St. Clement of Alexandria says, “God is one, and He is more than one, beyond unity.”³⁶⁵

361 St. Athanasius of Alexandria, Four Discourses Against the Arians 2.36 (NPNF II/4:368).

362 Athenagoras, A Plea for the Christians 10 (ANF 2:133).

363 Cf. St. Athanasius of Alexandria, Defence of Dionysius 17 (NPNF II/4:182).

364 Athenagoras, A Plea for the Christians 8 (ANF 2:132–133).

365 St. Clement of Alexandria, The Instructor 1.8.71 (FOTC 23:63).