Taken from NPNF (Second Series) vol 9.
In reviewing St Hilary’s thought, I will be relying primarily on Geofrey Bromiley’s Historical Theology for clarification on more difficult points. In no way can Hilary’s work be considered a literary masterpiece. It is about one hundred pages too long, repetitive, and wordy. To be fair, he wrote much of it in exile and like Augustine, was not always privy to the more mature Eastern thinking (though Hilary rectified this in some ways).
Further, Hilary shouldn’t be read in isolation from his very important text, De Synodis. There Hilary explains how homoousion should function in theology. He writes (De Synodis 67-69)
There is also a third error, which takes ‘Father and Son of one substance’ to indicate a prior substance, which the two share equally. The orthodox will assert ‘one substance of Father and son’; but he must not start from that: nor must he hold this as the chief truth, as if there could be no true faith without it.
Hilary begins his theology with God’s revelation. We know God as he reveals himself to us. However, our theologizing about God will always be opaque. God is invisible, ineffable, etc., and the mind grows weary trying to comprehend him (ii.6). Language itself fails us as words are powerless (ii.7). Analogies offer some help but they only hint at the meaning (i.19).
Trinitarian theology for the church begins with the baptismal formula in St Matthew’s gospel. The Father is the origin of all; the Son is the only-begotten, and the Spirit is the gift (ii.1). As the source of all the Father has being in himself. The fullness of the Father is in the Son. Because the Son is of the Father’s nature, the Son has the Father’s nature. Hilary’s point is that like nature begats like nature.
In a break with pagan thought, Hilary distinguishes between person and nature: “nor are there two Gods but one from one” (ii.11).
Hilary and the Spirit
Did Hilary teach the Filioque? It’s hard to tell, and neither camp should draw hard conclusions. The facts are these: 1) in ii.29 the Schaff edition reads “we are bound to confess him, proceeding as He does, from Father and Son.” However, the foonote points out that there are alternative, more probable readings. It is acknowledged that throughout Hilary’s work the text has been corrupted at parts. Even assuming the present reading to be the correct one, one must ask if by procession Hilary would mean the same thing as later Filioquist writers? The Latin word for proceed (procedere) does not have the same range as the multiple Greek words for “proceed.” Roman Catholic scholar Jean Miguel Garrigues notes that one simply can’t read English translations of the Latin semantic domains of “proceed” and from that infer, quite simplisticly, that Hilary believed in the Filioque (L’Esprit qui dit «Père!» (Paris 1981), pp. 65-75.; [no, I don’t read French).
2) Hilary goes on elsewhere to affirm that the Spirit is from the Father alone (viii.20) and the Father through the Son (xii.57); neither of these texts, obviously, are hard Filioquist reads, and in any case, this wasn’t Hilary’s point.
As an anti-Arian text, there is a reason why the Church spends more time with St Athanasius, Ambrose, and the Cappadocians. The Cappadocians and St Ambrose would later refine Hilary’s argument.
The Eucharist: St Hilary draws an analogy between the “of one nature” with Father and Son and the utter reality of the Son in the Eucharist. We receive the very Word make flesh in the Eucharist, not due to an agreement of will but because the Son took man’s nature to himself.
We know God by his operations or powers (later theologians would say energies): God’s self-revelation displays his Name (Person). This reveals his nature (i.27).
Rejects philosophical nominalism: names correspond to realities (ix.69).
On the Rock of Matthew 16.19ff: “This faith it is which is the foundation of the Church; through this faith the gates of hell cannot prevail against her” (vi. 37). The faith of the apostles, not the see of Peter, is the foundation of the Church.
It is not a literary masterpiece, nor is it really an outstanding apologia against Arianism. However, it is a faithful reflection of the Tradition passed down, and it does give many remarkable “snapshots” of the Church’s belief which can inform, challenge, and hopefully change the minds of folk today.