"The intellectual historian has to start with the words." – Richard Whatmore, What is Intellectual History?When political theorists write about the principle of popular power, that is, who are the people and what kind of power do they have – the language of ‘constituent power’ is a key concept in this regard. In her new book, Constituent Power: A History (Cambridge University Press, 2020), Lucia Rubinelli, a researcher in the history of political thought at Robinson College, Cambridge, retraces a history of the language of constituent power. Her book examines five key moments from Sieyes and the French Revolution, Schmitt over the Weimar Republic era, Arendt’s thought into the 1960s as well as less recognizable European jurists of the 19th and 20th centuries – all theorizing through these two words an understanding of popular power as an alternative notion to sovereignty as understood in their own contingent historical moments.This is the latest book in Cambridge University Press’s renowned ‘Ideas in Context’ series, as this well-researched thesis illuminates the history of key institutions of modern democracy from representation, electoral systems and constitutional courts among others in relation to the language of constituent power. Professor Rubinelli’s analysis brings to life what amounts to an intellectual history of the pivotal reinterpretations of Sieyes’s political thought and confirming with a flourish what Whatmore made clear in his book on intellectual history – "…it has to start with the words."Lucia Rubinelli is a junior research fellow in Robinson College at the University of Cambridge.Keith Krueger lectures at the SHU-UTS Business School in Shanghai.