Theory in the social sciences is not written in stone and undergoes change as it is continuously being tested in new research. This allows for an appreciation of the dynamic but also volatile nature of our subject matter, politics. While physicists have plenty of time to solve puzzles within a single and common theoretical frame, political scientists keep encountering anomalies that challenge their dominant theory. This tension between constancy and renewal has been and still is a prominent feature of Comparative Politics. Its challenges become especially evident in an Africanist perspective. Theory is generated in already “developed” or “democratic” societies, making Africa a poor fit. The main issue there is not the backsliding experience of countries with a democratic tradition. Instead, it is how to build democracy in a context where its benefits were denied the local population by the colonial administrators. This chapter is devoted to reviewing the theoretical constructs that political scientists have used to advance the comparative analysis of politics. It points to three main breakthroughs that have shaped Comparative Politics since its inception sixty years ago: structural functionalism, rational choice theory, and, in recent decades, democratic theory.