One of Margaret Cavendish’s most engaging and accessible texts, Sociable Letters (1662), is an epistolary exploration of a variety of topics relevant to the seventeenth-century reader, from women’s friendship and marriage to politics and civil war. While she shows her familiarity with royalist perspectives throughout, in the frequently quoted Letter #16, Cavendish enters civil war and Engagement debates about the proper derivation of a subject’s obligation and offers a powerful argument about women’s political status and their relationship to the state. If women do not take oaths, she reasons, then they must be neither citizens nor subjects of the Commonwealth. This chapter examines Cavendish’s strategic focus on oath-taking as a signifier of proper citizenship. In suggesting that women may not be bound to the state, Cavendish set herself apart from royalism, and from members of her own circle, including her husband and Thomas Hobbes. Her “no-citizen-no subject” argument belongs in the long history of women’s political writing, offering a perspective on women and the state that resonates with the later writings of Abigail Adams and the Seneca Falls Declaration of Sentiments.