"the beatific vision is thus the sole instance in which an act of the will is wholly free and wholly subject to its own natural necessity. . . . in stark contrast to modern voluntarism . . . the soul enjoys such delightful spontaneity only because she has been created with a natural desire for supernatural fulfillment.
"This conception of the beatific vision is an important bulwark against the misleading objection that Hilary's teaching implies that the Word did not suffer 'naturally' or 'spontaneously.' . . . The beatific act that perfects human nature cannot make us less human. . . . Christ's impassibility—the unique integrity of his body and soul—is precisely what allows him to experience pain more vehemently and so identify with those who suffer in a way that we cannot. . . . Christ's freedom from pain's tyranny cannot make him less free. . . .
"Just as perfect impassibility ensures that Christ feels suffering and sorrow all the more vehemently, the perfect love the beatific vision enables Christ to accept that suffering and sorrow with a perfectly natural spontaneity. Christ's possession of the beatific vision not only guarantees that his humanity is a perfect instrument (in the properly Thomistic sense of the phrase), it also ensures that his sacred body suffers in the mystical proportion necessary to reconcile the world to himself. His saving atonement, the consummation of love and spontaneity, requires nothing less than perfect impassibility. More importantly, the two are theologically inseparable: The suffering that Christ obediently undertook as a necessary component of his mission—'He learned obedience from what He suffered' (Heb. 5:8)—becomes true passion by dint of the perfect and total cooperation afforded by the beatific vision that Christ possessed from the moment of his conception—'For this I was born, and for this I have come into the world' (John 18:37).
"And so it remains that Christ felt the force of his suffering without its sorrow, for his suffering was made all the greater by the impassible nature he had from the Father, coursing into the soul that bore his body across the waters, that shook his sacred body with tears for his friend Lazarus, that blazed in his transfiguration like fire flashing from an alabaster jar. That Hilary saw no need to trisect Christ into deity, soul, and body is his strength. But if we must import the later categories of divine and human nature, considered abstractly, into his meditations, we can see that the medieval and early modern treatments of Hilary largely make more sense than most of our contemporary historical treatments. Knowing full well the difficulties that surrounded Hilary's peculiar vocabulary, these theologians confronted the difficult passages of De Trinitate with the the same ardor, but without the same perplexity, as many of their modern successors. Having never forgotten the spiritual importance of impassibility, they applied the necessary distinctions in the serenity afforded by their common tradition. They maximilized the Patristic tradition, to be sure, but they also humanized Christ, and their joint contribution to Christology shows us that impassibility—properly understood—allows Christ to suffer more, not less; allows him to do so with greater freedom, not less; allows him to embody the maximal love (John 15:12) and nothing less. It allows, in sum, God's power to be made perfect in weakness (2 Cor. 12:9), and so overcome weakness once and for all."
Trent Pomplun, "Impassibility in St. Hilary of Poitier's De Trinitate," in Divine impassibility and the mystery of human suffering, ed. James F. Keating and Thomas Joseph White, O.P. (Grand Rapids, MI: William B. Eerdmans Publishing Company, 2009), 211-213 (187-213).