This volume is an edited collection of the philosophical correspondences of three English women of the eighteenth century: Mary Astell, Elizabeth Thomas, and Catharine Trotter Cockburn. The selected correspondence includes letters to and/or from John Norris, George Hickes, Mary Chudleigh, Richard Hemington, John Locke, Ann Hepburn Arbuthnot, and Edmund Law. Their epistolary exchanges range over a wide variety of philosophical subjects, from questions about the love of God and other people to the causes of sensation in the mind, the metaphysical foundations of moral obligation, and the importance of independence of judgement in one’s moral choices and actions. The volume includes a main introduction by the editor, which explains some of the key themes and developments in the eighteenth-century letters, including an increased awareness of other women’s writings and of the concerns of women as a sociopolitical group. It is argued that if we look beyond printed treatises to the content of these letters, it is possible to gain a fuller appreciation of women’s involvement in philosophical debates of the 1690s and early 1700s. To situate each woman’s thought in its historical-intellectual context, the volume includes original introductory essays for each principal figure, showing how her correspondence relates either to her contemporaries’ ideas or to her own published views. The text also provides detailed scholarly annotations, explaining obscure philosophical ideas and archaic words and phrases in the letters. Among its critical apparatus, the volume includes a note on the texts, a bibliography, and an index.