... the institution of marriage is irreparably unjust. Its original and current meaning is to solidify male power in relation to women, and to draw an arbitrary line around legitimate relationships. Its historical function has been to use women as a means of forging alliances among men and perpetuating their "line." Today, when these functions are diminished but hardly absent, marriage's injustice consists primarily n its discriminatory granting of privileges. Marriage privileges specific ways of living and variously inhibits, stigmatizes, and penalizes other ways of living. A basic principle of liberal justice is that societal norms should regulate the rights and obligations of exchanges, relationships and institutional structures, without privileging some particular ways of life. The institution of marriage violates this principle, with oppressive and disadvantaging consequences for many people. If we are not to privilege particular relationships of ways of life, then what it means to be a family must be redefined and pluralized.
Iris Marion Young, "Reflections on Families in the Age of Murphy Brown: On Justice, Gender and Sexuality", in Intersecting Voices: Dilemmas of Gender, Political Philosophy, and Policy, Princeton: Princeton University Press, 1991