Stephen Holmes is probably the Trinitarian I appreciate and trust within the reflective Trinitarian theological community, as anyone who follows this blog probably realises (posts influenced by issues he raises can be seen here). In my paper Trinitarian Interpretations, I lean on his research and insights quite heavily. His core claim is that God is Trinitarian, but not tripersonal in the modern sense of the word "person". For Holmes, there is one divine personality, one mind, one will, one creator, yet three hypostases which are "God three times over", language he borrows I think from another "one-self" Trinitarian, Brian Leftow. These one-self Trinitarians are not modalists, but they are also not too developed on the distinctives between the hypostases of Father, Son and Spirit. The point is rather this: Holmes claims a radical re-working of Trinitarian doctrine in the last 100-150 years, culminating in "social Trinitarianism", combining three highly distinct persons into one God. There is a historical Trinitarianism from which modern social trinitarianism radically departs.
I wondered this morning if a similar kind of radical redefinition could be levelled at the Unitarians. Unitarians believe that God is one single being, comprising one person, the Father, to whom we have access uniquely through his perfect, glorious, and universe-entrusted Son, Jesus, and whose authority and presence is shared to his people through the sending by this Son, from the Father, of this Holy Spirit, as foretold long ago. OK maybe not all Unitarians express it like that, but I suspect and hope many of the Biblical Unitarian branch might have something like that in mind. So how might Unitarians have radically differed in more recent centuries to their predecessors?
Take the Arians or the homoisians (or homoians), for example. It is quite difficult to know exactly what they thought and taught as they were the "losers" of the great theological controversies of the fourth century. Indeed, we only have a version from the victors who, with Irenaeus perhaps setting the early precedent in 3rd century, were bent not only on showing how insane their position was, but also often to highlight their moral failings, corrupted minds, and so on, in order to discredit their opponents. However, in reading some of their polemical writings, we do learn of a fascinating difference, I think, with modern-day Unitarianism: the way in which they spoke of the Holy Spirit was interpreted by their anti-homoian opponents as that of a creature. The Holy Spirit is a creature? By this, clearly no-one understood a biological organism, but one that was created by God the Father, from whom all things derrive.
Today no-one believes that the Holy Spirit is a creature! Trinitarians understand this one as the third member of a Triune God, co-equal, co-glorified, consubstantial and co-eternal with the Father and the Son, intrinsically involved with all divine operations and action. Unitarians believe that this one is not really a person at all and point to the [ontologically] impersonal language most of the Bible speaks of the Holy Spirit and the subtle pushes of the translators toward a more personal depiction (e.g. all of the "who" you see in reference to the Bible could just as correctly, from a linguistic point of view, be translated "which" - did you know that?) They would (or should) rally around another theologically-developed idea of the Spirit being "God's empowering presence" (see Gordon Fee's classic work entitled precisely this way).