Minimizing Marriage: Marriage, Morality, and the Law, by Elizabeth Brake, Oxford University Press, 240 pp., $24.95.

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 about three 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.

These proposals will sound attractive to many libertarians who seek to make marriage a purely contractual matter. But Brake does not follow the path to complete privatization, arguing instead that caring relationships are "a good that the state should support." However minimal it may be, Brake's ideal of marriage still entails such traditional legal accompaniments as access to government benefits (mandatory spousal leave, tax-funded relocation assistance) that libertarians typically condemn as unjust, and exemption from legal requirements (immigration restrictions, duty to testify) that many libertarians would exempt the unmarried from too.

While Brake is a Rawlsian liberal rather than a libertarian, her ideal of "minimal marriage" is explicitly modeled on Robert Nozick's conception of the "minimal state"—the most extensive restriction compatible with justice. And like Nozick, Brake must fight a war on two fronts: against those who want more state restriction than minimal marriage offers, and against those who want less.

Against those who want more, Brake's arguments are bold, careful, and devastating. She takes as her starting-point the idea of liberal neutrality, according to which it is unreasonable to impose controversial conceptions of the good (even correct ones) on dissenting citizens, since respect for the coerced requires that coercion be justified in terms of reasons that they could accept. Liberal neutrality is often invoked on behalf of same-sex marriage, but for Brake, restrictions on multiple-partner marriages are no less problematic. And just as heteronormativity privileges opposite-sex relationships over same-sex ones, so "amatonormativity" (Brake's coinage) privileges amorous relationships over other caring relationships such as friendships. Thus, the state violates liberal neutrality when it allows controversially amatonormative views about good human relationships to shape marriage law.

To concerns about children, Brake argues that childrearing and marriage are separate issues that should be legally decoupled. To worries that polygamy is frequently oppressive toward women, Brake counters that in the "small patriarchal religious communities" where polygamy flourishes, monogamy is no better; the solution is to combat oppression generally, not just the polygamous variety.

And in response to the University of Chicago law professor Mary Anne Case's argument that the legal function of marriage is the "designation, without elaborate contracting, of a single other person third parties can look to in a variety of legal contexts," Brake argues that however efficient this may be, it is unjust insofar as it privileges one marriage form over others. (Libertarian readers may be reminded of Kevin Carson's argument that "by providing a ready-made and automatic procedure for incorporation" and so reducing the associated transaction costs, the state has "tilted the playing field decisively toward the corporate form" and so "reduced the bargaining power of other parties in negotiating the terms on which it operates.")

Against those who want less than minimal marriage—i.e., those who favor making the terms of marriage a purely private matter—Brake maintains that caring relationships are "primary goods" whose value is agreed upon by virtually everybody, regardless of their more specific moral or religious convictions. States exist, in part, to ensure equitable distribution of primary goods; and since these goods are not controversial, the state's involvement does not violate neutrality. Here libertarians are likely to find her arguments less convincing. Neutrality worries aside, are states well-suited to the task of distributing primary goods equitably? The institution's track record does not inspire confidence.

Brake argues that simply privatizing marriage would "cede control of this still socially powerful institution to the churches and other private-sector groups," while continuing state involvement "makes equal access to marriage as a social status more likely." Yet this argument asks us to contrast a state sector imagined as reformed and improved, one whose apparatchiks have evidently read her book and taken her advice, with an unchanged private sector where her arguments have made no impact—in short, a world where marriage traditionalists still dominate public discourse but somehow never get elected. Is this a fair or plausible comparison? (Brake also maintains that the state is best suited to administer marriage because it is "centralized" and "not subject to market pressures," which to libertarian ears is like saying that because a certain material is highly flammable it's the best choice for home insulation.)

Brake dismisses the likelihood of "ludicrously large marriages," on the grounds that caring relationships "require that parties be known personally to one another, share history, interact regularly, and have detailed knowledge of one another." But whence this requirement? Epicurus famously numbered his friends (Facebook friends avant la lettre?) by the cityful. For those of us who have been reared on a more Aristotelean, exclusive conception of friendship, the Epicurean view may seem impoverished; but by the standards of political liberalism, can the superiority of Aristotelean over Epicurean friendship permissibly be invoked in the framing of marriage law without violating liberal neutrality?

Brake is also confident that in most cases "abuse of the right would have no major costs," and in any cases where it might, she recommends "bureaucratic oversight" and "tests like those now used by immigration officials" to determine whether caring relationships are genuine. But Brake's confidence about the rarity of costly abuse seems excessively optimistic; it's not hard to imagine acquaintances who plan, for unrelated reasons, to move to the same city marrying to obtain relocation assistance. Or, more excitingly, the members of a criminal conspiracy marrying one another to obtain immunity from testifying. As for immigration-style tests of the genuineness of marriages, not only are these notoriously intrusive, but they are likely to lead in practice to the imposition of a normalizing model of the sort Brake seeks to avoid.

Still, one need not be a Rawlsian to think that, so long as the state is involved in areas where by libertarian standards it shouldn't be, there's a prima facie case for its involvement at least being conducted in as nondiscriminatory manner as possible. Perhaps roads should be privatized, but given that the state is currently building and funding them, they clearly should be open to drivers of all creeds, races, etc.; the analogous point holds for marriage law. And by libertarian standards, immigration restrictions are arguably a worse injustice—more destructive of people's lives—than, say, tax-funded relocation benefits; so Brake's proposal would involve less total injustice than the current system. Minimal marriage, then, has a serious claim to libertarian support.

All the same, minimal marriage has its risks, even as a second-best option. As Judith Butler warns in her essay "Is Kinship Always Already Heterosexual?": "To be legitimated by the state is to enter into the terms of legitimation offered there and to find that one's public and recognizable sense of personhood is fundamentally dependent on the lexicon of that legitimation." Just as libertarians are divided as to whether to focus their efforts on petitioning the state for more liberty—inevitably, on the state's terms—or on building alternative institutions that bypass the state entirely, a similar choice faces those who favor marriage equality.

Roderick T. Long is a professor of philosophy at Auburn University and the president of the Molinari Institute.