Amélie has posted some thoughts on this encyclical and the comments to her thread suggest that there is much interest in it. However, some of the comments are a bit inane. For example, one guy sees this Encyclical as an olive branch to “gays” because B16 does not explicitly limit eros to heterosexuality and limit “gays” to agape. This sad thinking, besides being delusional, completely misunderstands the faith and the Trinitarian foundation of love. If one reads this Encyclical closely, he will see that same-sex eros can never be purified.  One can never acheive same-sex agape (here I mean in the sense of which we call the disorder of same-sex attraction).
Part of the problem with understanding what unity in difference can mean is a lack of a proper metaphysics. Orthodox theologian, David Bentley Hart does a masterful job in Beauty of the Infinite of showing that the errors of post-modernism reduces to monistic presuppositions about the Being of God. This error of monism leads post-moderns to see God as in competition with creation and so in opposition to man, especially in terms of freedom. What Msgr. Robert Sokolowski calls the Christian difference, solves this problem.  God is ontologically different than creation as His is Uncreated Being, where creatures possess created being. Hart demonstrates that these are not at two opposite poles of the same dimension of being with the finite on one end and the Infinite at the other. Rather created being ex-ists by participation in Uncreated Being (which sub-sists). Infinite Being is not the sum of all beings, it is Being Itself.
This type of false opposition is at the heart of other confusions, including Trinitarian theology and the theology of love. Eros and agape are not two different types of love in opposition to one another but two aspects of the unity which is love.  Like the distinction in Persons in the Unity of the divine nature, the distinctions of love do not eliminate love’s unity.
As the title of the Encyclical says, God is Love. God is perfection itself and so Love, and loves distinctions into eros and agape are logical distinctions which allow understanding of the different manners in which created being participates in the simplicity of God’s Being. These distinctions are proper to created intellect, but making these distinctions shouldn’t be confused with complexity in God.
Love is an act of the will in which one selflessly gives himself as a gift to others. But this gift of self is the result of a developing process (in creatures) which is the culmination of a love of attraction. The attraction (eros) is not annihilated but it achieves its end in the self-gift (agape). Eros, in our fallen state, must be purified in agape. Neither is this self-gift static. It is an on-going act of the will; it is a decision to give oneself as a gift and to receive the other likewise, in response.
What some folks seem to miss is that eros as we experience it, can and many times is, distorted. B16 addresses that and makes it clear that eros which is not grounded in self-gift is a distortion which strips love and the lover of dignity and humanity. So what is and is not authentic self-gift?
Self-gift can only be rooted in Trinitarian love. The Father’s total gift of Himself to the Son and the Son’s reciprocation are fruitful. This mutual Love is a Person . . . the Holy Spirit. Being the Source of everything that exists, this total self-giving establishes the framework for creation and so it is the interpretive key for understanding creation and most especially the human person who is created in the image of this Self-giving God.
This framework shows that love must be true to the order of creation. This is where those who mistakenly believe that B16 is somehow now saying that same-sex genital relations are suddenly not a disorder, completely miss the Trinitarian nature of creation. The Encyclical says that “…man is somehow incomplete, driven by nature to seek in another the part that can make him whole, the idea that only in communion with the opposite sex can he become ‘complete’” (DCE 11). Here B16 follows JPTG’s theology of the body in which the latter shows that man is made, male and female, in the Trinitarian image. Husband and wife are a unity in difference, made complementarily for one another. The structure of heterosexual anatomy demonstrates their complementarity and their having been ordered to the one-flesh union which is the only genital union that has the capacity to be fruitful in a life-giving way.
B16 uses the phrase unity and difference also to describe the hylomorphic union of body and soul. Because the soul is the substantial form of the body, the body expresses something in the soul. This includes sex differences.  Sex differences are ontological and created for the unity in difference of love, manifested in its dimensions of eros and agape.Â
So no Virginia, there is no Santa Claus…there is nothing here but wishful thinking to suggest homo-eroticism can be included in anything but a “warped and destructive form” of eros (DCE 4).
Now while marital love is the most clear place to demonstrate this unity and distinction, B16 does not do this. I suppose that JPTG’s theology of the body, to which I find unmistakeable allusions, has already done that. Here, B16 makes these distinctions in the unity of love as the prelude to what I believe may be a new development in Church social teaching and perhaps even in ecclesiology. I will share those next time.