Efforts to explain evil are as old as humanity itself. The figure of the devil has condensed these attempts like no other symbol. Still open, the debate about whether the devil is a being that really exists or is just an image that has served to represent sin is resumed here to delve into the problem of evil: its origin, power and presence in human life. This work unitarily collects a set of texts, with the aim of helping to free us from superstitious terrors through a natural explanation of the so-called diabolical possessions and to emphasize that the truly possessed is the one who oppresses others. From different analyzes of what the Holy Scripture, Theology and the Magisterium of the Church state about the devil, to the evolution of this figure in history and its approach by science, psychoanalysis and philosophy, The authors reflect on how the devil is, to a large extent, an ideological resource that has been used to avoid assuming our freedom with responsibility. This book allows us to remember that since time immemorial we have faced an eminently human problem that we have not been able to solve: the evil we inflict on each other.