Many great thinkers have wrestled with the topic of evil. St. Thomas Aquinas's disputed question <i>On Evil</i> merges as the longest and most comprehensive study on the subject of evil available. This long-awaited translation is based on the critical edition of the Latin text published by the Leonine Commission in 1982. The disputed question <i>De malo (On Evil)</i> was first presented as a series of oral debates at the University of Paris (1263-1272?) and subsequently recorded in the form in which it now appears. The length of the work and the thoroughness of the treatment is eloquent testimony of the importance St. Thomas attached to this topic.