An abbreviated history of marriage helps motivate the question of whether ancient Roman marriage and contemporary love marriage could qualify as stages of the same (token) institution despite carrying significantly different functions, deontological powers, and constitutive rules. Having raised the question of institutional identity over time, I proceed to answer the question by appealing to Kurt Lewin's notion of genidentity. Lewin intends the notion of genidentity to track the spatiotemporal unfolding of different physical and biological processes, such as ontogenesis. I (...) extend the notion of genidentity to the institutional sphere by identifying two ‘re-anchoring mechanisms’ that would describe the conditions under which institutions with different characteristics could nevertheless qualify as the same institution across time. First, formal institutions can be re-anchored by way of a self-amending secondary rule. Second, informal institutions can be re-anchored by leveraging the inherent indeterminacy of the exemplars that indexically define them. I then argue ancient Roman marriage and contemporary love marriage are genidentical in virtue of the actions of a (mostly) informal re-anchoring mechanism. (shrink)