| Ours is arguably the era of codified constitutions. Today about 200 countries, both democratic and authoritarian, have a constitution. But have constitutions lived up to the great political and social expectations vested in them? Have they worked? Answering this apparently straightforward question turns out to be extremely challenging. The road to its response is studded with conceptual, theoretical and empirical difficulties.;The objective of this manuscript is to contribute to the first step by clarifying what we mean when we say that a constitution works. How constitutional efficacy is conceptualized has important theoretical, empirical, and normative implications. The objective of this manuscript is to present and defend the conceptualization of constitutional efficacy as the prevalence of constituted motivations. I focus on the organic part of the constitutions. Grosso modo, we can say that if these provisions do work they must create and organize a certain type of governmental power and roles, which I call constitutional power and constitutional roles respectively. My argument is that when constitutional roles are invested in an individual, she receives special kinds of motivations, which I call "constituted motivations". The account of constitutional efficacy I defend is understood to be the prevalence of those motivations in the behavior of individuals holding constitutional roles. I argue that this conceptualization is empirically useful, theoretically sound, and normatively sensitive.;The manuscript is divided into three parts. First I provide the conceptual and theoretical grounding of my thesis. Second, I defend the conceptualization of constitutional efficacy as the prevalence of constituted motivations: I argue that it satisfies the criteria of a satisfactory conceptualization of constitutional efficacy; I contrast it with the three main alternatives, and I discuss the different types of constitutional inefficacy implied by it. The third part delves into the history of political thought, and of constitutionalism in particular. Its main goal is to explain how constitutional efficacy as the prevalence of constituted motivations relates to some central elements of constitutionalism. |