Besides the obvious inclination towards spying the love of a man and a woman in these theological reflections, I could not help but think of Icons.
Balthasar is not explicit in limiting the particular object and subject to human beings, only to consciousness (he rejects objectification of conscious being as fit for tools like mathematical equations or cooking utensils). It is natural to interpret these musings in relation to human love or Divine love. Yet the life of Icons seems to fit these categories if we understand what iconography is. Above all, Icons leave their mark on their subjects whose supplications are an imprint which breathes life into the Icon. The entire dynamics Balthasar describes here would well serve as a description of the mystical relation of prayer with the Icons.
As to the broader question of freedom and intimacy, one spies all of the excitement if German theology here. The argument against conflating scientific understanding of the material world with understanding of the essence of the material world is of course correct, but I suppose I am puzzled that anyone would make this mistake. Only in the West does one spy this insane debate between interlocutors who have proven scientifically that God does not exist and those who have proven scientifically that he does. Science is forever silent on the subject of God. God is not the object of scientific inquiry.
Balthasar's virtue in this chapter rests in categorizing what we often think of as mystery, essence or truth as intimacy. Intimacy is indeed the best characterization for that which is beyond the grasp of universal comprehension and always subjective. A universal truth subjectively known and incommunicable - the most frustrating of truths for the Western mind!
Kierkegaard and Nietzsche came closest to perceiving such a thing, but both failed due to impatience. What Balthasar offers us is that great gem of Catholic thought: discipline. He demands that we resist the urge to see some concrete thing in the chain of abstraction formed by his argument. It is a task almost impossible for the lay reader, whose mind immediately offers up numerous concrete things to match each abstract idea.
To succumb to this temptation would be to miss the forest for the trees. Each abstraction is a link on a great chain leading to God. Yet each concrete embodiment of that abstraction is incompatible with every other concrete embodiment. The urge to pronounce that this paragraph of Balthasar's is "really" about marriage, that paragraph about science and so forth would quickly transform theologics into wise aphorisms on a range of subjects.
While doing so would not necessarily be harmful to the moral health of readers, it would not do justice to Balthasar's writing. His insistence to remain in the realm of abstraction is an invitation to spiritual cleansing. In combating the urge to connect the abstract to the particular, readers train their souls in stripping away the world in order that they might glimpse the face of God carried on the wings of Balthazar's logic. It is a carmelite journey, a Siberian exile. It is also the path through which the universal and abstract becomes the personal and intimate. The God we see at the end of this theological argument will be the God of the universe encountered in intimacy and thus incomprehensible to others. Our own. What disturbs me in Balthasar's argument is the concept of freedom. This Western preoccupation with freedom is the surest path towards its loss...
(Thoughts on Book I of Theologik)