Perfect love unites Father, Son and Holy Spirit. Standard theology of the Trinity states that the Holy Spirit is the love between the Father and the Son. The obvious relational conclusion is that Father and Son love love, indeed love perfect love perfectly.
Standard theology states that Father, Son and Holy Spirit have, in their divinity, one intellect, one will and one power. The relationship between Father and Son makes it clear that the will of God is ascribed first and foremost to the Father. We could say, then, that Son and Holy Spirit share in the intellect, will and power of the Father. These capacities are infinite.
In "Deus caritas est," Pope Benedict XVI distinguished between eros and agape love. He pointed out that human love is perfected when love of God and love of neighbor are perfectly united. He pointed out that the human person is perfected when body and soul are perfectly united. It is also the case that the love of God in the immanent Trinity is the perfect union of eros and agape, and that both eros and agape are perfectly motivated by who and what each person is. Furthermore, the motivation of human love is perfected when it is ordered to God first, and when love of neighbor is derivative of and motivated by love of God and love of God's love.
God's love of humanity is perfectly compassionate and perfectly merciful. God's love, both eros and agape, of the human person is motivated, in part, by his original design and purpose for the human person. God's knowledge that, in his fallen nature, man can be restored to original grace through forgiveness, repentance and purification of the human soul gives added purpose to God's agape love. That added purpose, of course, is derivative of God's original purpose to divinize humanity.
This perfect love of God for humanity is reflected in a particularly significant way in the love of a priest for a penitent. That love is a reflection of the love that motivated Jesus to descend into hell to bring back those who had been lost prior to his definitive act of redemption. The harrowing of hell is repeated again and again in the confessional when the priest receives the confession of a child of God who repents of grievous sin and when the priest gives absolution. Adam and Eve committed a grievous sin in doubting the perfect love of God and looking for an alternative path to divination. Although Genesis does not report on their repentance, it is clear that tradition finds that they repented of their sin before they died.
A priest who hears a confession of grievous sin is confronted with evil, indeed with twisted humanity, indeed the deepest form of human ugliness. The priest's love, if he is to be a fit instrument of God's love, must overcome, nay overwhelm, his natural revulsion at the ugliness. That revulsion must be replaced by compassion, the recognition that he, himself, is capable of such evil and that the person before him is a child of God very like himself. In this recognition, the priest must be able to see beyond the ugliness and see the limitless potential for good that can be present within the soul of the true penitent. In other words, the priest must be able to see the potential that God sees. His motivation for loving the penitent must be a reflection of God's motivation.
Understanding this, we can begin to appreciate the nature of Christ's love for humanity. In spite of our spiritual ugliness, Christ, in his perfect compassion, stands ready to offer superabundant mercy and forgiveness, and he sacrificed his very life in a truly ugly and painful death in order to remain faithful to that love. To have avoided that torture and death would have meant that he considered his own life to be more important than his identification with humanity. In avoiding what appears to us to be needless suffering, he would have put distance between himself and his torturers. As ugly as his torturers were, Christ hated the distance more.
Christ's perfect love motivates perfect identification. His declaration of that identification, recorded in Matthew 25, must be understood in this way.
Divine love leads to divine identification. Indeed, in appreciating this, we can begin to appreciate more fully how it is that God's will is one and perfect.