Trinity is a hard concept to understand. There are three persons in God. Yet, the Old Testament emphasizes:

• The exclusive unity of God (Deut 6:4; 5:7–11).
• Alludes to the plurality of God (Gen 1:2, 26; 11:7; 18:1–33; Exod 23:23).
• This plurality of God in the OT, Isa 42:1 and 48:16, comes very close to a Trinitarian formulation.

The New Testament does not have any explicit statement on the Trinity—

• 1 John 5:7, is referred to by many but it has been rejected as a medieval addition to the text.

Notwithstanding, Trinitarian evidence is overwhelming.

• Jesus is clearly described as divine in the gospel of John (John 1:1–3; 20:28).
• Jesus, himself, proclaims his own divinity (John 8:58).
• In the NT, we find references to the three persons of the Godhead:
  • All three are mentioned at the baptism of Jesus (Matt 3:16–17).
  • During the Lord’s Supper, Jesus comforts his disciples with the thought that he and the Father would send the Holy Spirit to guide them after his departure (John 14:16–17).
  • All three persons are part of the baptismal formula found in Jesus’ great commission to his disciples (Matt 28:19).
  • Paul readily refers to all three persons in many of his epistles (Rom 8:9–11; 2 Cor 13:14; 2 Tim 1:3–14; Eph 1:13–14; 3:14–19).
  • Peter acknowledges the work of Father, Son, and Holy Spirit in the salvation of people (1 Pet 1:2).
  • John is a witness of the Spirit’s testimony regarding Jesus, the Son of God (1 John 5:5–9).
  • The book of Revelation also presents three persons involved in the final events of this world (Rev 1:4–5; 22:16–18).

All these biblical evidence to the triune God causes concern for some people because the Holy Spirit is often referred to with metaphors of objects:

• A dove (Matt 3:16)
• The wind (John 3:8)
• Fire (Isa 6:6, 7)
• Water (John 7:37–39)
• Oil (Matt 25:1–4)

In addition, New Testament statements appear to refer to Jesus as having had a beginning when he is referred to as “begotten” (monogenes) or “firstborn of all creation” (prototokos) (John 3:16; Col 1:15).

In history, the doctrine of the Trinity in the early church struggled with the Trinity. When the early church addressed it through a series of councils confirming the eternal divinity of Jesus. With the acceptance of Jesus as Savior and Lord, the Trinity quickly found its way into the creeds of the church.

The Niceo-Constantinopolitan creed

Please Note: Later western versions of the Nicene Creed added the filioque clause:

The addition of this clause was one of the issues that led to the great schism between east and west in 1054.

The early church fathers gave us the vocabulary we use and discuss today:

• Irenaeus spoke of the “economy of salvation,” in which each member of the Godhead has a distinct yet related role.
• Tertullian argued that “substance” is what unites while “person” is what distinguishes the members of the Godhead. “The three persons of the Trinity are distinct, yet not divided, different yet not separate or independent of each other.” 
• The eastern Cappadocian fathers expanded on Tertullian’s thought and tended to emphasize the distinct individuality of the three persons while safeguarding their unity by stressing the fact that both the Son and the Spirit derived from the Father. Note: Cappadocian fathers, Orthodox theology teaches that the Son is the “only begotten” of the Father and the Holy Spirit “proceeds” from the Father. 
  • They spoke of one “substance” (ousia) in three “persons” (hypostases).” 

One needs to be aware the that vocabulary and thought used today assumed ancient Greek dualism and metaphysics, which are very distant and confusing to us now.

Augustine's theology of the Trinity was based on the concept of relationship and on the bond of love between Father, Son, and Holy Spirit. This doctrine continued to experienced challenges to this day.

• Arianism holds that the Son was created by nature and did not exist before the Father brought him into existence. As such the Son is subordinate to the Father’s authority (subordinationism). Arians have also consistently denied the personhood of the Holy Spirit.

The many forms of Modalism:

• Sabellianism -- teaches that Father, Son, and Holy Spirit are three different modes or manifestations of the same God at different times.
• Monarchianism -- is a form of modalism that denied the plurality of God. It holds that the Father, Son, and Holy Spirit are a succession of modes or operations; they are not separate persons.
• Socinianism had been criticizing the doctrine of the Trinity on both biblical and rational grounds.

I don't accept the traditional Platonic dualistic worldview and metaphysics that were foundational to the church fathers’ theology of the Trinity, one of these being the concept of the immortality of the soul.

Do we have common ground on the development of this doctrine thus far? In view of the texts cited above isn't it clear that Trinitarian evidence is overwhelming? CM