Opponents of same-sex marriage are quick to raise the specter of polygamy. If “everybody should have the right to marry,” Rick Santorum asked on the campaign trail earlier this year, then “what aboutthree men?” While Santorum clearly intended this quip as a reductio ad absurdum of calls for marriage equality, the Arizona State University philosopher Elizabeth Brake argues in Minimizing Marriage that recognizing polygamous and polyamorous unions is not only required by justice but doesn’t go far enough.

For Brake, marriage not only should not be restricted to opposite-sex couples, or indeed to couples at all. It constitutes unjust discrimination, she argues, to restrict marriage to romantic or sexual relationships. Instead, the social and legal status of marriage should be available to “caring relationships” of all kinds (though not to Santorum’s further bugaboos of “man on child” and “man on dog” unions, since parties to marriage contracts must be legally competent). Moreover, the terms of such marriages should be flexible, rather than fixed by a state-imposed one-size-fits-all model; one might, as in one of Brake’s examples, choose to cohabit with a lover but confer one’s spousal health care benefits on an impoverished relative, and authority for end-of-life decisions on a close friend. The result is what Brake calls “minimal marriage”: marriage with minimal requirements for recognition.