While many Trinitarians will state that the creedal formulations of the Trinity are explicit in the Bible, more intellectually honest Trinitarians will admit such is not the case; instead, it comes from, at best, implicit biblical data coupled with doctrinal development, boiling the debate down to whether such is a natural/organic (“true”) evolution or a mutative (“false”) evolution; for a Protestant to argue such, it is a denial of the formal sufficiency of the Bible, as the Trinity, which is the most important doctrine, is not formally explicated! (for more on this, see my lengthy essay refuting Sola Scriptura, Not by Scripture Alone: A Latter-day Saint Refutation of Sola Scriptura)
Theologians agree that the Bible does not present a clear doctrine of the Trinity . . . The God of the Bible does not, then, merely float off the pages of Scripture; the doctrine of God arises from deliberate theological reflection. Theology continually systematizes that doctrine by the use of reason, based on biblical insights, and informed by the broad, historical Christian tradition. (Tim Reddish, Does God Always Get What God Wants? An Exploration of God’s Activity in a Suffering World [Eugene, Oreg.: Cascade Books, 2018], 10)
With respect to passages that speak of the Father, Son, and Spirit (e.g., Rom 8:22-28), Raddish elsewhere notes that such Triadic passages are not proof of the (Creedal) Trinity (cf. Does Matthew 28:19 support Trinitarianism? for an exegetical discussion of this popular Triadic passage):
It is important to note that this Trinitarian inference is from later theology, rather than explicitly from within this text. From a Trinitarian perspective, the Spirit need not utter anything, as the Father knows the Spirit’s intention without it being expressed. This reminds us that contemporary Christians read Scripture through a Trinitarian lens and, consequently, not everything is neat and tidy. (Ibid., 126 n. 22)
One has to give credit to Raddish for this level of intellectual honesty (compare and contrast with pop-level Trinitarian apologists like James White).
