Reasoning steps: The Trinity

Verdicts: F1 · The Trinity. Shared notes and post-750 development: trinity.

F01.1 (was trinity/T1): One God in three co-equal, consubstantial persons

Step F01.1.1: Scripture

Matt 28:19 (one ’name’ of Father, Son and Spirit); John 1:1 (θεὸς ἦν ὁ λόγος); John 10:30; 2 Cor 13:14; the Spirit as a personal Paraclete (John 14:16, 26).

Step F01.1.2: Patristic evidence

Ignatius (T1) calls Christ ‘God existing in flesh’. Tertullian (T2): ’three … of one substance’. Nicaea: the Son ὁμοούσιος with the Father. The 381 creed: the Spirit ‘with the Father and the Son together is worshipped and glorified’. Sources: ignatius-tri-s1 · tertullian-tri-s1 · nicaea-i-tri-s1 · constantinople-i-tri-s1.

Step F01.1.3: Weighing decision

There is no serious rival reading among the fathers after Nicaea; before it, Tertullian’s ‘degree’ language is subordinationist in wording but defends one substance. Verdict: Trinitarian consensus.

• Confidence: High.

Step F01.1.4: Source-proximity weighing

• Scripture (benchmark): The NT names Father, Son and Spirit together as the one God (Matt 28:19; 2 Cor 13:14) and calls the Son θεός (John 1:1; 20:28). The technical terms are later, but the substance is in the text. (Scripture confidence: high)
• Assessment: Supported at every tier from T1 and by Scripture. All nine traditions confess it classically (Dordrecht I: ‘Father, Son, and Holy Ghost, and in none more’).