Empirical studies in the sub-field of European state-building within political science have centered on material or institutional explanations for the development of the modern state. These cross-case analyses ignore key distinctions amongst cases, such as the importance of ideational factors in the modernizing process. This case study of the development of the British state looks at how changes in the conceptualization of the state and the nature of constitutionalism evolved over the course of the 17th century through the political writings of several influential theorists. This evolutionary process highlights distinctions in British constitutionalism between the personalist Union of the Crowns and the constitutionalist parliamentary Acts of Union. This study concludes with a discussion of the Scottish independence movement and the possible effects of the 2014 referendum on the British state.