I contend that analyses of state transformations would benefit from paying closer attention to state theory. Different theoretical answers to what the state is and how it came about lead to different answers in explaining state change. Four major theoretical traditions—class-analytic, liberal, neo-Weberian, and culturalist—are identified. The chapter considers the way in which each tradition conceptualizes (1) state-society relations, or the boundary between state and non-state actors and processes,(2) state capacity, or the ability to implement policy choices, and (3) consent to state power, or how states obtain compliance from citizens. Then I discuss the rise of the modern state through the lens of each theoretical tradition, as well as their explanations of state development in one key policy area: welfare policy. Finally, I explore the implications that the four state theory traditions have for the analysis of state change and for recent transformations of statehood.