If the Father, Son, and Holy Spirit had not made themselves personally known, we would not have attained knowledge that the one God is the triune God. A theology that operated without revelation might reason its way to abstract monotheism or to the polytheism of multiple divine agents working in the world, but triunity has to be carefully taught by God. John of Damascus [676-749 A.D.] speaks for the mainstream of Christian thought when he identifies divine self-revelation as the exclusive source of the confession of God’s triunity (Fred Sanders, The Triune God, 37).

“Trinitarian theology ought to be conducted in such a way that it maintains high standards of right speaking while enacting and enabling the movement of seeking God’s face” (Fred Sanders, The Triune God, 35).

“To join in the ancient Christian prayer called the Gloria Patri, directing praise to Father, Son, and Holy Spirit, is to come into alignment here in the world “as it is now” with triune glory “as it was in the beginning” (Fred Sanders, The Triune God, 25).

“All theology, not just that which takes place in the subregion of the doctrine of the Trinity, is marked by it s doxological provenance and orientation. . . . Theology is not itself if it is not also praise” (Fred Sanders, The Triune God, 27-28).

“It often seems that while patristic books about the Trinity were mostly about the Bible, even the best modern books about the Trinity are mostly about the church fathers. As long as it can be done without amnesia or ingratitude, the most patristic way to proceed is, after all, to study Scripture” (Fred Sanders, The Triune God, 24).

We say that the righteousness which the Spirit of God works through us is, not the cause, but the testimony of the righteousness in which alone we can appear before God. We maintain that eternal life belongs to us of right, as being co-heirs of Christ, but nevertheless freely (Rom 8:12-17). Now, if we enquire [sic] in whom, properly speaking, this righteousness resides, we will only find it in the Person of Christ alone. But, in the measure in which He was given to us, whoever takes hold of Him by faith, possesses Him eternally, — as, by God the Father, He was made for us wisdom, righteousness, sanctification and redemption (1 Cor 1:30), — thus, His righteousness is also made ours; it is imputed to us. To this alone we hold, on this alone we totally rely, for it alone is perfect (Theodore Beza, The Christian Faith, 29).

In ourselves we are but dead and rotten stumps; it requires grace to make us living and good trees before we can yield one good fruit (Theodore Beza, The Christian Faith, 28).

But, among the fruits that faith produces universally in all true Christians, we esteem the invocation of the name of God through Jesus Christ to be principal; this is what we call ‘prayer’ (Theodore Beza, The Christian Faith, 23).

From Church History by Eusebius.

Then at last, when all humanity throughout the world was now ready to receive knowledge of the Father, that same divine Word of God appeared at the beginning of the Roman Empire in the form of a man, of a nature like ours, whose deeds and sufferings accorded with the prophecies that a man who was also God would do extraordinary deeds and teach all nations the worship of the Father. They also predicted the miracle of his birth, his new teaching, the wonder of his deeds, the manner of his death, his resurrection from the dead, and, finally, his restoration to heaven by the power of God.”

From the Preface of Joseph A. Fitzmyer’s commentary on Romans.

In fact, one can almost write the history of Christian theology by surveying the ways in which Romans has been interpreted.