Here is Hugh Binning (1627-1653), young Scottish theologian, speaking of the primacy of God’s life as the ground of salvation; speaking of the primacy of God’s love as the foundation of salvation:
. . . our salvation is not the business of Christ alone but the whole Godhead is interested in it deeply, so deeply, that you cannot say, who loves it most, or likes it most. The Father is the
very fountain of it, his love is the spring of all — “God so loved the world that he hath sent his Son”. Christ hath not purchased that eternal love to us, but it is rather the gift of eternal love . . . Whoever thou be that wouldst flee to God for mercy, do it in confidence. The Father, the Son, and the Holy Ghost, are ready to welcome thee, all of one mind to shut out none, to cast out none. But to speak properly, it is but one love, one will, one council, and purpose in the Father, the Son, and the Spirit, for these Three are One, and not only agree in One, they are One, and what one loves and purposes, all love and purpose.
As Thomas Torrance notes further, after Binning wrote what we just read from him, he cited Gregory Nazianzen thusly: “I cannot think upon one, but by and by I am compassed about with the brightness of three, and I cannot distinguish three, but I am suddenly driven back unto one.” What a beautiful way to think of the One in Three/Three in One, the Triunity of Godself when considering the depth reality of what has taken place in salvation.
And I would like to suggest to Katherine Sonderegger, who is concerned about the De Deo Trino (Threeness of God) crowding out the De Deo Uno (Oneness of God), and who attributes a Trinitarian emphasis to doing theology in the 20th and 21st centuries to the impact of the modern theological move primarily made by Karl Barth, that there is evidence to the contrary. I.e. This example from Binning helps to illustrate how Oneness and Threeness were not only thought together for the pre-moderns in the post-Reformation period, but it also underscores how Threeness was a prominent reality for the patristics, as Binning himself appeals to Nazianzen. Note Sonderegger’s concern:
… Perhaps nothing so marks out the modern in systematic theology as the aversion to the scholastic treatise, De Deo Uno. It belongs not the preface but rather the body of the dogmatic work to lay out the broad movement in present day dogmatics that has pressed the treatise De Deo Trino to the fore; indeed, it crowds out and supplants the exposition of the One God. But even here we must say that the doctrine of the Trinity, however central to the Christian mystery, must not be allowed to replace or silence the Oneness of God. God is supremely, gloriously One; surpassingly, uniquely One. Nothing is more fundamental to the Reality of God that this utter Unicity. Such is God’s Nature; such His Person: One. Oneness governs the Divine Perfections: all in the doctrine of God must serve, set forth, and conform to the transcendent Unity of God….
I would submit that Sonderegger creates a false disjunction by speaking of Oneness over against Threeness, and vice versa. We see Binning creatively think Oneness into Threeness and vice versa in a way that I should think would be instructive for Sonderegger. She also uses numbers for God in a way that actually flattens out the mystery she is claiming to enhance and magnify by emphasizing God’s Oneness; Bruce McCormack drives this home when he writes:
… The doctrine of the Trinity is not one doctrine among others but the presupposition of all other Christian doctrines. It is this because triunity is not something added to “oneness” but is a description of what God is essentially. Put another way: the trinitarian relations are not laid on top of a divine essence which has been “established” metaphysically (i.e. in abstraction from those relations as a “fourth” beneath or behind the “persons”). The relations simply are what God is essentially. For that reason, as Karl Barth argued, it will not do to treat the “one God” before treating the “triunity” of God because everything that needs to be said about the “one God” needs to be conditioned by what is said about the Trinity….
… Suffice it here to say that the logic of numbers, as applied to God, is employed responsibly only where it is recognized that numbers too never rise above the level of analogical predication. Used univocally of divine “persons’ and “human” persons, they are bound to mislead. Seen in this light, to speak of the “one” God is not merely to refer to the metaphysical concepts of singularity or uniqueness. The “unity” of Jesus Christ with His Father is a relation that includes (even if it is not exhaustively described by) the love each has for the other.
For a Christian conception of God it is not possible or recommended to try and think of God as One or Three outwith the other; there is no Oneness of God without His Threeness, and no Threeness without His Oneness. Binning understood this, pre-modern that he was, and indeed helps to uplift the mysterious wonder of who God is, and who this God is with us and for us.
 Hugh Binning, Works, 89 cited by Thomas F. Torrance, Scottish Theology: From John Knox to John McLeod Campbell (Edinburgh, Scotland: T&T Clark, 1996), 79.
 Ibid., 79.
 Katherine Sonderegger, Systematic Theology, Volume One: The Doctrine of God (Minneapolis: Fortress Press, 2015), XIV.