Thanks to Jay Dyer for this.
“According to St. Maximus, God is “identically a monad and a triad.” Capita theologica et oeconomica2, 13; P.G. 90, col. 1125A.He is not merely one and three; he is 1=3 and 3=1. That is to say, here we are not concerned with number as signifying quantity: absolute diversities cannot be made the subjects of sums of addition; they have not even opposition in common. If, as we have said, a personal God cannot be a monad — if he must be more than a single person — neither can he be a dyad. The dyad is always an opposition of two terms, and, in that sense, it cannot signify an absolute diversity. When we say that God is Trinity we are emerging from the series of countable or calculable numbers. St. Basil appears to express this idea well: “For we do not count by way of addition, gradually making increase from unity to plurality, saying ‘one, two, three’ or ‘first, second, third.’ ‘I am the first and I am the last,’ says God (Isaiah 44:6). And we have never, even unto our own days, heard of a second God. For in worshipping ‘God of God’ we both confess the distinction of persons and abide by the Monarchy.” De spiritu sancto18; P.G. 32, col. 149B.
The procession of the Holy Spirit is an infinite passage beyond the dyad, which consecrates the absolute (as opposed to relative) diversity of the persons. This passage beyond the dyad is not an infinite series of persons but the infinity of the procession of the Third Person: the Triad suffices to denote the Living God of revelation. St. Gregory of Nazianzus, Or. 23 (De pace 3), 10; P.G. 35, col. 1161. Or. 45 (In sanctum pascha); P.G. 36, col. 628C.If God is a monad equal to a triad, there is no place in him for a dyad. Thus the seemingly necessary opposition between the Father and the Son, which gives rise to a dyad, is purely artificial, the result of an illicit abstraction. Where the Trinity is concerned, we are in the presence of the One or of the Three, but never of two
“The monad is set in motion on account of its richness; the dyad is surpassed, because Divinity is beyond matter and form; perfection is reached in the triad, the first to surpass the composite quality of the dyad, so that the Divinity neither remains constrained nor expands to infinity.” St. Gregory of Nazianzus, Or.23 (De pace3), 8; P.G. 35, col. 1160C. See also Or. 29 (Theologica3), 2; P.G. 36, col. 76B.