Of all the reactions I’ve seen to my recent blog post against gay marriage, the one that surprises me the most (besides Frankie Machine’s half-assed non sequitur) is the curious counter-claim that homosexual marriage should be permissible because straight people who cannot or will not reproduce can also get married.

I think people who raise the “sterile heterosexual” rebuttal believe they’ve advanced an intellectually serious counterfactual to my central claim, but I don’t think their logic holds.

Let’s begin by assuming that my central argument is correct and we all concede that by definition, marriage is no more and no less than a legally and culturally respected contractual framework that provides for the rearing of children and offers a socially useful infrastructure for protecting and privileging close-kin relationships while legitimizing the intergenerational transfer of property.

The state’s compelling interest in supporting child rearing — augmented by a series of tax benefits and an inheritance mechanism — confers publicly financed incentives, some of which are conditioned on the actual production of children and some which are latent in the structure of the marriage institution itself. People who take advantage of those financial benefits without producing offspring are functioning as free riders: They’re being unfairly enriched by participating within a system for which they aren’t entitled to membership, draining the state’s resources without upholding their end of the baby-making bargain.

A few observations:

1. That heterosexual free riders unfairly benefit from marriage doesn’t mean that homosexuals also deserve a free ride. It’s illogical to claim that one abuse of a system justifies a second abuse; the logical solution is to limit heterosexual free ridership, instead of opening the floodgates to homosexuals. This counterpoint highlights the most significant deficiency with the “sterile heterosexual” rebuttal.
2. In a practical sense, it’s very easy to see that homosexual couples are biologically incapable of procreation. Heterosexual couples, by contrast, are almost never obviously sterile; the only way to tell for sure whether a heterosexual couple is capable of procreating is to subject both parties to invasive and expensive fertility testing. Were the state to require fertility testing as a prerequisite to obtaining a marriage license, the result is either a very steep bill for the state (and almost surely, in the aggregate, failing a cost/benefit analysis) or the effective restriction of marriage only to the wealthy (which contradicts the purpose of marriage as the optimal family structure for child rearing). The least-worst outcome is probably something very similar to what we have today: Marriage open to heterosexuals on the belief that enough will procreate to justify the public expenditure on tax benefits without incurring extra costs assocated with new barriers to entry.
3. In a cultural sense, admitting non-fecund heterosexuals into the institution of marriage serves a secondary purpose of reinforcing the desirability of marriage as a normative family structure. Socializing children to look to marriage as a bedrock social arrangement serves a useful public purpose in itself — enough, I think, to partially mitigate the free rider problem for sterile couples.

Thus, although sterile heterosexuals are certainly a problem, they’re not the problem that gay-marriage advocates think. The free-rider nature of non-fecund heterosexual unions is a defect that requires amelioration, not a systemic defect that therefore justifies gay marriage.

Indeed, it’d be more rational to exclude known sterile heterosexuals (e.g., the elderly) than to include homosexuals within the marriage institution, because as long as the state provides taxpayer-funded benefits to married couples, then the state incurs a cognate obligation to ensure that those tax dollars are expended for that purpose with as little “leakage” as possible. Free riders constitute a “leak” in the system — one that should be plugged, not enlarged.

From a purely public perspective, the only way to get around the free rider problem is to create an institution (e.g., civil unions) that don’t confer the same family-raising economic benefits as marriage.

If, and only if, the state removes all child-rearing economic benefits from the institution of marriage, does it make sense for the state to sanction marriage among the homosexual sterile or deliberately non-fecund.

Until then, no number of childless married couples will ever justify opening floodgates to even more free riders.