I generally would steer away from this type of discussion for fear the mods think I become too indelicate in this discussion, but because so many have voiced concern over this teaching, I feel compelled to, as “delicately” as possible, address this issue.
First, as Rau so eloquently stated, marriage, let me repeat that “MARRIAGE”, is inherently a sexual union between a man and woman. As Casey pointed out, and I think merits repeating, it is important to understand what the word marriage means. “To cause to meet or ‘fit together’; combine.”
So, that being said, let me get to the indelicate part:
Second, in order to validly marry, a couple must be capable of engaging in the “marital act”. Inability to do so is known as impotence; HOWEVER, that is very RARELY a reason for not recognizing a marriage these days given medical advances, both chemical and mechanical, that make a man’s inability to engage in the marital act almost nonexistent.
Without getting too technical, let me just cite to the following:
The church is certainly not insensitive to the concerns that people face every day. Nonetheless, it is the last bastion against the attacks of secularism upon age old accepted, (and ordained by God I might add) teachings, including the immutable understanding that marriage is:
An indissoluble covenant between one man and one woman ordered toward their own good (unity) AND toward the procreation and education of children.
Now, we could get into a discussion about what “ordered toward procreation” means, but suffice it to say that first, there are innumerable threads already on that issue, and second, in short hand as already said here, it simply means being able to “do IT”.
I hope that is clear without crossing any bounds.