On the Fall of the Devil
Anselm of Canterbury's De Casu Diaboli (On the Fall of the Devil) is a theological treatise written around 1085 as a companion to his earlier work on free will and the nature of evil. Composed during his time as abbot of Bec, before becoming Archbishop of Canterbury, this dialogue emerges from the same intellectual ferment that produced his famous ontological argument for God's existence. Anselm wrote it to address fundamental questions about the origin of evil and the mechanics of angelic and human sin that had puzzled Christian thinkers since Augustine.
The work unfolds as a philosophical dialogue between teacher and student, examining how rational creatures capable only of good could nevertheless choose evil. Anselm argues that the devil's fall resulted not from any deficiency in his creation, but from his failure to persevere in the good for which he was made. The devil possessed justice—the disposition to will what he ought—but abandoned it by willing more than was appropriate for his nature. This abandonment represents the essence of sin: not the willing of something evil in itself, but the willing of something good in a disordered way. Anselm extends this analysis to human sin, arguing that all rational creatures fall through similar acts of non-perseverance rather than through any positive corruption of their nature.
De Casu Diaboli has remained influential because it offers a sophisticated account of moral evil that preserves both divine goodness and creaturely responsibility. Anselm's precise reasoning about the relationship between freedom, justice, and sin shaped medieval discussions of these topics and continues to inform contemporary philosophical theology. The work demonstrates his characteristic method of using rigorous dialectical reasoning to illuminate mysteries of faith.
Who should read this: Students of medieval philosophy and theology seeking to understand classical treatments of the problem of evil, and anyone interested in how rational analysis can illuminate questions of moral responsibility and the nature of sin. This is not light spiritual reading but demands careful attention to philosophical argument.