This book provides new approaches to the debate on individuality and non-individuality in quantum mechanics, with chapters written by leading experts in the field. A significant issue in the philosophy of quantum mechanics, the choice between individuality and non-individuality, and the well-known metaphysical underdetermination between these options in quantum theory, receive here new treatment, including metaphysical, logical, and methodological analyses. Scholars and students engaged in the philosophy of quantum mechanics and the metaphysics of science, as well as philosophers concerned with the impact of quantum mechanics on their disciplines will find this book to not only new proposals and arguments for the various sides of the debate, but also new venues for exploring the subject further.