“Not every marriage can fulfill both purposes, but it must fulfill at least one purpose...A potent man can be infertile: i.e. he may be able to have an erection but unable to produce viable sperm.”
That’s interesting. I wasn’t familiar with this aspect of Catholic teaching. Just curious, though — what is the barrier to gay marriage then? I always thought the problem was that it wasn’t procreative. However, it could certainly be argued to be unitive. If it’s the erection you’re after, aren’t two erections better than one?
Marriage is between a man and a woman - the Scriptural injunction specifically asserts that a man and a woman become one flesh in marriage, and Scripture further clarifies that intercourse between man and man is an abomination.
It is also biologically obvious that the conjoining of two reproductive systems - not a reproductive system and a digestive system - is the design of human nature.
Is homosexual sex unitive? I don’t think it is. What is it that is uniting? Purely on the physical level, as wideawake indicated, it’s hard to see how sperm cells are in any way uniting with the cells of someone’s descending colon. With natural intercourse, there is a true union and true fusion that results in a new human being.
The only possible uniting that could be going on between two men is spiritual. But you can share a spiritual bond with all kinds of people without bedding them, so I’m not sure why sodomy enters into the picture.
Essentially, what homosexuality does is that it seeks a good—the spiritual union of two souls—and then improperly moves it into a sexual venue. A while back I read some testimony from folks who had “lived the life” and then for various reasons left it. Many of them were very clear about their psychological motivations—they said they craved male companionship, but no matter how many men they slept with, they could never find it. To me, biology aside, that’s Exhibit A of the non-unitive nature of homosexuality.