The Trinity is a revealed mystery in the biblical sense of the word mystery. And it is not enough to list it alongside other mysteries, because it concerns the entire scope of salvation history and makes known the actual identity of God. As a doctrine covering territory so deep and wide, it is a mystery without peers; it is the one primordial mystery of God’s being and works. The triunity of God has always been, was once concealed, and is now revealed. The manner of its revelation should establish the order and structure of the doctrine concerning it, as well as the order and structure of adjacent doctrines like revelation and salvation (Fred Sanders, The Triune God, 68).

We will be arguing throughout this book that the Trinity is a biblical doctrine. But it is not enough to say that the mystery of the Trinity is in the Bible unless we recognize that the thing we are calling the Bible is a set of texts that were written, redacted, and canonized to prepare for and report on the missions of the Son and the Spirit. To somebody about to come through the texts to find the elements of the doctrine, we have to say: the Trinity is in the Bible because the Bible is in the Trinity (Fred Sanders, The Triune God, 44).

A doctrine of revelation uninformed by Trinitarian realities could not be the proper setting for the doctrine of the Trinity (Fred Sanders, The Triune God, 42).

But the doctrine is also, in another and higher sense, more revealed than most doctrines. The root idea of revelation is not verbal announcement but the unveiling or disclosing of something that has been present, though concealed. In order to inform us that the Father has a Son and a Holy Spirit, the Father sent the Son and the Holy Spirit in person. The triunity of God was revealed when the persons of the Trinity became present among us in a new way, showing up in person and becoming the object of our human observation. The apostles testified that what they saw with their eyes and touched with their hands was “that which was from the beginning,” because it “was with the Father and was made manifest” to them (1 John 1:1-3). Doctrines that are first announced verbally have a character of revealedness less directly; the doctrine of the Trinity has it more directly. There are profound reasons that the doctrine of the Trinity has this special status, but at this point it is sufficient to note that this is in indicator that the doctrine of the Trinity is more than just another doctrine on the list of true things we have been taught by God about God. It is God’s self-revelation by way of presence in a more direct, intense, and personal way (Fred Sanders, The Triune God, 40).

The doctrine of the Trinity is a revealed mystery. It is in some ways less revealed than other doctrines, and in other ways more revealed. It is less revealed in this sense: it is not directly proposed in the words of Scripture and presented to us in a formulated state. Some doctrines are. . . . But the triunity of God is not made known in that way. It is not set forth in oracular idiom in the Old Testament (“Thus saith the Lord: I am Father and Son and Spirit”), nor is it made the subject of focused and deliberate teaching in the New Testament (“Now concerning the persons of God, I would not have you ignorant . . .”). The basic vocabulary of Trinitarian theology is not found on the surface of the text (person, nature, relation, threeness), and the conceptual elements of Trinitarianism are not gathered in one place and related to each other by Scripture itself. We nevertheless call it a revealed doctrine, and even a biblical doctrine, because, as the Westminster Confession of Faith reads, “the whole counsel of God . . . is either expressly set down in Scripture, or by good and necessary consequence may be deduced from Scripture.” The triunity of God is among those things “by good and necessary consequence deduced” from what is “expressly set down.” To call it less revealed than other doctrines is simply to admit, with calm confidence and equanimity, that it is not verbally formulated for us, and that some assembly is required (Fred Sanders, The Triune God, 39-40).

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).