The De Malo represents some of St Thomas Aquinas's most mature thinking on goodness, badness, and human agency. Together with the second part of the Summa Theologiae, it is one of his most sustained contributions to moral philosophy and theology and ranks among his major writings. In it Aquinas examines the full range of questions associated with evil: its origin, its nature, its variety, its relation to good, and its compatability with the existence of an omnipotent, benevolent God. This edition offers the Leonine Commission's authoritative edition of the Latin text with a new, clear, and readable facing-page English translation by Richard Regan. Brian Davies has supplied an extensive introduction and notes.