Below is the next question in Chytraeus’ primus locus, or first topic, on God. (It’s been a while; the previous installment is here.)
The reason that only three persons are to be recognized in the Godhead is because that is what God has revealed in Scripture. Chytraeus again asserts his foundational Scripture-principle: that our knowledge of God comes from God’s revelation of himself, which we find in his Word. Christian dogmatics and worship is to be established upon the foundation of the Prophets and Apostles. In support of his Scripture-principle Chytraeus cites Deuteronomy 4:12 and part of Isaiah 8:20, though the rest of the verse and much of the rest of the chapter is relevant.
Cur tantum tres personae Divinitatis agnoscandae et invocandae sunt, & non plures vel pauciores?
Quia DEUS sic se patefecit in baptismo Christi, & in institutione baptismi nostri & aliis testimoniis. Mat: 28. Baptizate eos in nomine Patris & Filii, & Spiritui Sancti. Psal: 2. Dominus dixit ad me, Filius meus es tu, osculamini Filium. Psal: 33. Verbo domini coeli firmati sunt, & spiritu oris eius omnis exercitus eorum.
Fundamentum autem totius doctrinae Theologicae est haec sententia: Quod not aliter sit de Dei essentia, & voluntate & cultibus ipsi praestandis sentiendum aut docendum, quam sicut se Deus, in suo verbo, per Prophetas & Apostolos tradito, patefecit.
Deuter: 4.12. Non addatis ad verbum, quod vobis loquor, nec auferetis ex eo. Esaiae: 8. Si non dixerint iuxta verbum hoc, non erit eis matutina lux.
Why ought only three persons of the Godhead to be recognized and called upon, and not more or fewer?
Because God has revealed himself thus in the baptism of Christ, and in the institution of our baptism and other testimonies. “Baptize them in the name of the Father, and of the Son, and of the Holy Spirit” (Matt. 28). “The Lord said to me, you are my Son, kiss the Son” (Ps. 2). “By the word of the Lord the heavens were made firm, and by the spirit of his mouth the whole host of them” (Ps. 33).
The foundation, moreover, for all theological doctrine is the following proposition: that one must not think or teach about God’s essence and will and the worship that should be given to him otherwise than as God has revealed himself in his own Word, handed on through the Prophets and Apostles.
“Do not add to the word that I speak to you, nor take anything away from it” (Deut. 4:12). “If they will not have spoken according to this word, they will not have the morning light” (Is. 8).