Pat Lee — professor of bioethics at Franciscan University of Steubenville — has an article up at The Public Discourse on the nature of marriage and why it is inherently heterosexual.
The whole thing is well-worth a read, but one section in particular struck me when I read it:
[C]o-habiting same-sex couples form one relationship. If later they decide to collaborate in raising an adopted child, they form a new and distinct relationship, since there is no intrinsic link between their sexual relationship, on the one hand, and their cooperation to raise a child, on the other. Unique to marriage is the fact that the bodily, emotional, and volitional relationship between the man and the woman is intrinsically oriented to being prolonged and fulfilled by their becoming a family. It is the same community that begins between the spouses on their wedding day, and may be prolonged and enlarged by becoming a family later on. (Emphasis added)
It’s somewhat common-sensical, but I was struck by the observation that in marriage, the community that is the couple is intrinsically structured (oriented) towards prolongation, while in same sex relationship, there is no intrinsic holistic ordering towards children, but rather a new relationship is formed when a same sex couple adopts.
As I said, it struck me in a particular way. Interesting.