One of the key aspects of the Augustan settlement, and more generally of the early Principate, was the firm control of the princeps over public religion, including the main priestly colleges. This paper sets out to consider several related problems: what place-if any-did the expertise that priests deployed in the performance of their duties have in that period? How did emperors engage with it? What impact did it have on the workings of the Senate? How can these issues shed light on the interplay between politics and religion at a time of profound historical change? * Aspects of the argument of this paper were presented in Oxford and Erfurt in November 2014 and January 2015 respectively, and I greatly benefited from the questions and reactions of the audiences on both occasions. I am very grateful to Nicholas Purcell and Jörg Rüpke for illuminating discussion, and to my late colleague John Moles and two anonymous referees for invaluable comments on drafts of this piece.