Seventeenth-century English dramatists produced several ‘disguised duke’ plays in which a ruler disguises himself to reinforce political control. Critics typically view these as a call for monarchs to address corruption at court. But such readers have largely ignored the epistemological shift represented: knowledge is based on circulation among, observation of, and dialogue with citizens rather than on textual traditions. Together, the plays legitimise the knowledge and experience of observers immersed in London’s daily life, playwrights included. Moreover, the disguised ruler motif also contributed to the social practices through which ‘new’ empirical forms of knowledge gained authority.