Though Descartes never wrote a book specifically devoted to moral philosophy, his thought on ethical matters can be found throughout his correspondence and in parts of his work Passions of the Soul. In 1685, an anonymous editor in London gathered these writings in a textbook devoted to Descartes's ethical thought.
Roger Ariew has translated, from Descartes's original French texts, those selections included in the 1685 volume, adding to those writings an Appendix of relevant materials, including Part III of the Discourse on Method on the provisional morals, a portion of the Preface to the French edition of the Principles of Philosophy on the "tree" of philosophy, and portions of additional letters that help to illuminate the background for the correspondence included in the 1685 volume.
Ariew's insightful Introduction explains the contexts in which Descartes addressed ethical questions, the reasoning behind his reluctance to write specifically about moral issues, and the significance of what this collection of writings reveals.