Anne Conway was an extraordinary figure in a remarkable age. Her mastery of the intricate doctrines of the Lurianic Kabbalah, her authorship of a treatise criticising the philosophy of Descartes, Hobbes, and Spinoza, and her scandalous conversion to the despised sect of Quakers indicate a strength of character and independence of mind wholly unexpected (and unwanted) in a woman at the time. Translated for the first time into modern English, her Principles of the Most Ancient and Modern Philosophy is the most interesting and original philosophical work written by a woman in the seventeenth century. Her radical and unorthodox ideas are important not only because they anticipated the more tolerant, ecumenical, and optimistic philosophy of the Enlightenment, but also because of their influence on Leibniz. This fully annotated edition includes an introduction which places Conway in her historical and philosophical contexts, together with a chronology of her life and a bibliography.