Is Marriage a Natural Function?

Marriage is that which unites men and women to one another. This is true even if the couple can no longer have sex, such as if one or both partners becomes impotent. As long as they came together at least once, then they're married because they became one flesh. That's why impotence is an impediment to marriage. If you legally redefine marriage to accommodate same sex couples, then you lose the rational basis for rules like this. It just becomes dating with a fancy certificate and a bunch of legal fees.