A brief submitted to the U.S. Supreme Court concerning the California case by conservative professors Leon Kass and Harvey Mansfield and the Institute for Marriage and Public Policy warns that “the social and behavioral sciences have a long history of being shaped and driven by politics and ideology.” And research about, for example, the stability of same-sex marriages or child-rearing by same-sex couples is “radically inconclusive” because these are recent phenomena and they provide a small sample from which to conclude that these innovations will be benign.

Unlike the physical sciences, the social sciences can rarely settle questions using “controlled and replicable experiments.” Today “there neither are nor could possibly be any scientifically valid studies from which to predict the effects of a family structure that is so new and so rare.” Hence there can be no “scientific basis for constitutionalizing same-sex marriage.”

The brief does not argue against same-sex marriage as social policy, other than by counseling caution about altering foundational social institutions when guidance from social science is as yet impossible. The brief is a preemptive refutation of inappropriate invocations of spurious social science by supporters of same-sex marriage.