The protagonist of this study, the Jesuit Martin Delrio (1551-1608), is a largely forgotten figure, purposefully elided from many of the scholarly and religious spheres to which he contributed. To the extent that he is remembered today it is for his Disquisitiones magicae (1599-1600), a study of witchcraft and superstition that went through numerous editions and was last reprinted in 1755. The present volume recovers the lost world of Delrio's wider scholarship and shows that the Disquisitiones, removed from this context, has been widely misunderstood.