Classical theism and trinitarian thinking

One of the other things I've been pondering (mainly while in Doctrine of God classes or revising for the exam on Friday) is the link between statements of God's attributes and trinitarian thinking. Can we afford to have one without the other?

Hilary of Poitiers in de trinitate links together a discussion of God's attributes with his relational being (why he made it onto my list of 30 things to be thankful for). I was reading him in relation to my Doctrine of God essay on incorporeality, omnipresence and perichoresis.

Here are some of the things he said that I really liked:
‘His merciful and mysterious self-revelations are in no wise inconsistent with His true heavenly nature; and His faithful saints never fail to penetrate the guise He has assumed in order that faith may see Him [...] God was seen and believed and worshipped as Man, Who was indeed to be born as Man in the fullness of time. He takes upon Him, to meet the Patriarch’s eye, a semblance which foreshadows the future truth.’

Hilary explicitly denies that the eternal Son had a human form before the incarnation – although he may have been manifest in the theophanies, in taking on human flesh in the incarnation he assumes a body he did not have before that time:
'He had the fullness of the Godhead; he has it still, for He is God’s Son. But He Who was the Son of God had become the Son of man also, for The Word was made flesh. He had not lost His former being, but He had become what He was not before; he had not abdicated his own position, yet He had taken ours.'

Hilary explores this perichoretic relationship and demonstrates that the nature of the eternal Son is determined by the unbegotten Father. He argues that the Father begat the Son in eternity not from any pre-existent matter, nor from nothing, by childbirth or as a piece of himself. Rather: ‘Incomprehensibly, ineffably, before time or worlds, He begat the Only-begotten from His own unbegotten substance, bestowing through love and power His whole Divinity upon that Birth. Thus He is the Only-begotten, perfect, eternal son of the unbegotten, perfect, eternal Father.’

In taking on human form for our salvation, the external Son is embodied, however, like the Father, he remains essentially invisible, bodiless and incomprehensible: ‘the Son is mysteriously omnipresent in the same way as the Father […] If the mutual indwelling of the Father and the son is understood in a bodily way, this is an impossibility. ’ Faced with an embodied Son, Arians must reject the mutual indwelling of the Father and Son, because they argue the Son is less than the Father. Hilary counters a suggestion that omnipresence and perichoresis are inconsistent by acknowledging that what may seem impossible for human understanding is possible for God to be: ‘It seems impossible that one object should be both within and without another, or that (since it is laid down that the Beings of whom we are treating, though They do not dwell apart, retain their separate existence and condition) these Beings can reciprocally contain One Another, so that One should permanently envelop, and also be permanently enveloped by, the Other, whom yet he envelopes […] what man cannot understand, God can be.’