Moved here from notes/reasoning/trinity.md in the tier migration. The per-question reasoning now lives on each doctrine’s reasoning page: F01.1 · S15.1.

The Trinity and the filioque: reasoning steps

Verdicts: categories/trinity.md. Method: conventions and proximity tiers. Scripture is the primary measure; fathers are weighed by tier (T1 to c. 150 = 1.0, T2 = 0.8, T3 = 0.6, T4 = 0.4).

Post-750 development by tradition

Catholic

Toledo (589) onward; Florence (1439).

• T1 (fathers 4/4; Scripture 4/4): Lateran IV; Athanasian Creed.
• T2 (fathers 2/4; Scripture 2/4): Florence (1439): from the Father and the Son ‘as from one principle’; creed insertion.

Orthodox

Photius; Blachernae (1285): ’through the Son’ as eternal manifestation.

• T1 (fathers 4/4; Scripture 4/4): Dositheus 1.
• T2 (fathers 3/4; Scripture 4/4): From the Father; Photian ‘alone’ sharper than ’through the Son’.

Oriental Orthodox

Nerses Shnorhali; Gregory of Tatev.

• T1 (fathers 4/4; Scripture 4/4): Nerses: ‘one essence, one sovereignty, one power and one glory’ (verified).
• T2 (fathers 3/4; Scripture 4/4): Nerses Shnorhali: ’emanating, as to its essence, from the Father alone’ (verified).

Lutheran

AC I with the Western creeds.

• T1 (fathers 4/4; Scripture 4/4): AC I.
• T2 (fathers 2/4; Scripture 3/4): Filioque in the Nicene and Athanasian creeds as used.

Anglican

Art. I and V.

• T1 (fathers 4/4; Scripture 4/4): Art. I.
• T2 (fathers 2/4; Scripture 3/4): Art. V: ‘proceeding from the Father and the Son’.

Presbyterian

WCF II.

• T1 (fathers 4/4; Scripture 4/4): WCF II.3.
• T2 (fathers 2/4; Scripture 3/4): WCF II.3: ’eternally proceeding from the Father and the Son’.

Reformed Baptist

1689 ch. 2.

• T1 (fathers 4/4; Scripture 4/4): 1689 2.3.
• T2 (fathers 2/4; Scripture 3/4): 1689 2.3: ‘proceeding from the Father and the Son’.

General Baptist

Orthodox Creed 3, 38.

• T1 (fathers 4/4; Scripture 4/4): Orthodox Creed 3 and the three creeds (to verify article).
• T2 (fathers 2/4; Scripture 3/4): Receives the Nicene and Athanasian creeds in the Western form (Orthodox Creed 38; to verify wording).

Anabaptist

Dordrecht I.

• T1 (fathers 4/4; Scripture 4/4): Dordrecht I: ‘one eternal, almighty, and incomprehensible God, the Father, Son, and Holy Ghost’ (verified).
• T2 (fathers n/a/4; Scripture n/a/4): Dordrecht and Schleitheim do not address the procession.