In United States v. Windsor, the Second Circuit reasoned (no doubt, correctly) that extending federal marriage benefits to all married couples—both same‐ and opposite‐sex—will not affect the incentives of heterosexual couples to marry, and therefore should not threaten any state interest in encouraging marriage among heterosexuals who, by force of desire or nature, may be inclined to produce children as a result of their mutual lust. Finding no state interest sufficiently compelling to justify what appears to be an irrational classification, the court declared DOMA unconstitutional. The Supreme Court may or may not reach the substantive merits of Windsor. But if it does, the responsible procreation argument warrants greater attention, not because the Second Circuit’s conclusion was wrong, but because the reason the argument fails is quite a bit weightier than the Second Circuit’s mechanical treatment of it suggests. The responsible procreation theory fails not because it is bizarre or incoherent. It fails because the argument behind it rests on premises that are no longer true—if they ever were—and because the exclusions it suggests, however coherent, are now simply cruel and unwarranted. Just as importantly, the failure of the responsible procreation justification for the exclusion of same‐sex couples from marital benefits also suggests the irrationality of the exclusion of other forms of family—and indeed, of single individuals—from this form of federal largesse.