One God, Three Persons

“Hear, O Israel: The LORD our God, the LORD is one.” — Deuteronomy 6:4

The Christian doctrine of the Trinity confesses one God who exists eternally in three persons. This is not a contradiction but a mystery revealed progressively through Scripture. The God who is echad (אֶחָד) — “one” — is a unity that encompasses real personal distinctions. The Nicene Creed (325/381) and the early councils that followed gave the Church the language to confess this mystery with precision, guarding it against the heresies that would collapse the persons into one (modalism), divide the essence into three (tritheism), or subordinate the Son and Spirit below the Father (Arianism).

The Oneness of God

Scripture is unambiguous that there is only one God:

“I am the LORD, and there is no other, besides me there is no God.” — Isaiah 45:5
“There is one God, and there is one mediator between God and men, the man Christ Jesus.” — 1 Timothy 2:5

The Hebrew word echad (אֶחָד) in the Shema (Deuteronomy 6:4) denotes a unity that can be composite — the same word describes the “one flesh” of husband and wife in Genesis 2:24.

Three Distinct Persons

The New Testament reveals that within the one divine being there are three distinct persons, each fully God:

The Father

Identified as God throughout Scripture (1 Corinthians 8:6; 1 Peter 1:2)
Sends the Son into the world (John 3:16; Galatians 4:4)
The source from whom all things come (1 Corinthians 8:6)

The Son

Called God explicitly: “The Word was God” (John 1:1); “our great God and Savior” (Titus 2:13). In John 1:1, the term Logos (λόγος) — “Word” — carries immense theological weight. In Greek, logos meant reason, speech, or ordering principle; in Jewish usage it echoed the creative Word of God by which the heavens were made (Psalm 33:6). John’s declaration kai theos ēn ho logos (καὶ θεὸς ἦν ὁ λόγος) — “and the Word was God” — places theos (θεός, “God”) in the predicate position without the article, indicating that the Logos has the full nature of God while remaining personally distinct from the Father (who is “God” with the article, ton theon / τὸν θεόν, earlier in the verse). This is not “a god” but God in essence.
Exercises divine prerogatives: forgives sins (Mark 2:5–7), receives worship — proskyneō (προσκυνέω), the same word used for worship of God alone (Matthew 14:33; Hebrews 1:6)
Existed before creation and is the agent of creation (John 1:3; Colossians 1:16–17). Paul calls the Son the eikōn (εἰκών) — “image” — of the invisible God (Colossians 1:15), not a mere likeness but the exact visible manifestation of the unseen Father
Philippians 2:6 says He existed “in the form of God” — en morphē theou (ἐν μορφῇ θεοῦ). Here morphē (μορφή) refers not to outward shape but to the essential nature and attributes that make something what it is. The Son possessed the very nature of God before He “emptied Himself” — ekenōsen (ἐκένωσεν) — by taking on human nature (Philippians 2:7)

The Holy Spirit

Called God: Peter equates lying to the Spirit with lying to God (Acts 5:3–4). For a fuller treatment, see the article on the person of the Spirit. The Greek Pneuma (πνεῦμα) — “Spirit” or “breath” — corresponds to the Hebrew Ruach (רוּחַ), the same “Spirit of God” who hovered over the waters at creation (Genesis 1:2)
Possesses divine attributes: omniscience (1 Corinthians 2:10–11) — the Spirit “searches” (eraunaō, ἐραυνάω) even “the depths of God” (ta bathē tou theou, τὰ βάθη τοῦ θεοῦ) — omnipresence (Psalm 139:7–8)
Acts as a person — He teaches, testifies, intercedes, and can be grieved. The verb lypeō (λυπέω) — “to grieve” — in Ephesians 4:30 implies a personal, relational being, not an impersonal force (see also John 14:26; Romans 8:26–27, where the Spirit intercedes with “groanings” — stenagmois, στεναγμοῖς — too deep for words)

The Persons Distinguished

The three persons are not merely different names for the same individual. Scripture presents them in personal relationship:

The Father sends the Son (John 6:38); the Son prays to the Father (John 17)
The Father and Son send the Spirit (John 14:26; 15:26)
At Jesus’ baptism, all three are simultaneously present and distinct: the Son is baptized, the Spirit descends, and the Father speaks from heaven (Matthew 3:16–17)

Key Theological Terms

The church developed precise language to guard the biblical teaching:

Homoousios (ὁμοούσιος) — “of the same substance.” The Son is of the same divine essence as the Father, not a lesser or different kind of being. Affirmed at Nicaea (325 AD).
Hypostasis (ὑπόστασις) — “person” or “subsistence.” Each of the three is a distinct hypostasis while sharing the one divine ousia (οὐσία) — “essence” or “being.”
Perichoresis (περιχώρησις) — “mutual indwelling” or “interpenetration.” The three persons eternally dwell in one another in perfect love and communion (John 14:10–11; 17:21). There is no separation, no rivalry, no division — only the fullness of shared life. John of Damascus (c. 675–749) gave this concept its classic formulation in De Fide Orthodoxa, describing a ceaseless circulation of life and love among the three persons.

One God — Not Three

The Trinity is not three gods cooperating. The three persons share one undivided divine essence, one will, one power, and one glory. Every outward act of God — creation, providence, redemption — is the work of all three persons, though each may be especially associated with a particular role. The Father creates through the Son by the Spirit (Genesis 1:1–3; John 1:3; Psalm 33:6).

“I and the Father are one.” — John 10:30

In this verse, “one” is the neuter hen (ἕν) — “one thing,” one in essence — rather than the masculine heis (εἷς), which would mean “one person.” Jesus claims unity of nature with the Father while preserving personal distinction. His Jewish opponents understood this perfectly: they picked up stones because He was “making himself God” (John 10:33). The deity of Christ and the deity of the Spirit, together with the Father’s divinity, constitute the one triune God — the mystery that stands at the heart of Christian worship and the foundation of every other doctrine.

“The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all.” — 2 Corinthians 13:14