Many of those who oppose legalizing same-sex marriage argue that it amounts to “redefining” marriage. Well the answer to that is, no it doesn’t, it depends, you’re the ones who are redefining marriage, it’s been redefined many times, only a little bit, and so what?
The definition of marriage put forward by opponents of SSM is, “a union between a man and a woman”. If SSM is legalized, the definition would be, “a commitment between two people who are romantically in love, share a sexual bond, and plan to maintain a household as lifelong companions”. So any aspect of marriage that gays are capable of fulfilling is removed from the definition and what we are left with is a man and a woman unionizing. No love, no sex, no commitment, no soul-matery, no building a home together, just rote mating.
Opponents emphasize that marriage is thousands of years old, is integral to the “fabric” of society, and is vital for propagating the species. But how many couples would describe their own marriages in terms of these sorts of political archetypes? Most would define their relationships in more personal terms—how they feel about each other and the steady companionship they provide.
It’s misleading to call marriage an “institution” in that it implies it’s a singular entity that a small number of people could somehow ruin for everybody. Better to characterize it as a practice—the practice of creating small institutions, the fortunes of one having nothing to do with that of the others.
Allowing gays to marry is not going to overturn the entire archetype. It’s just a small exception in order to accommodate a small group of people who constitute an exception to normal patterns of human sexuality. There’s no redefinition for the majority of people.
And as significant as raising children is to a marriage, it clearly takes a back seat to the spousal bond itself, rather than being an absolute prerequisite in legitimizing any marriage. Couples marry who have no intention or ability to have children together. And people also divorce, cohabitate, and have children out of wedlock. These practices are legal and widely accepted—and have become more widespread as a result. But same sex marriage only applies to gay people. It’s not going to spread to the majority heterosexual population because sexual orientation is not contagious.