Various opinions and theories have appeared about the ontological question of good and evil from the time of Aristotle to now. This issue got more sensitive from the time it was considered to be a variable against the existence of God and his attributes. Some deem the existence of evil as the main and the only reason to deny the existence of God, while others have a view contradictory to this belief. In the eyes of John Hick and Augustine, evil is an existential entity. Influenced by the Irenaean theodicy, Hick gives in a new form to the definition of evil. Hick believes that evil is the lack of good and God is not the cause of evil, and introduces evil as a negative entity within a causal specification framework. With the provision of this theory, the casual principles also achieved special importance. In the study at hand, we investigate and criticize the metaphysical question of evil and its relationship with the existence of God from the viewpoint of John Hick. To this end, first the principles of good and evil are presented and then, the important question of “the role of evil in the causal structure of creation” in Hick’s and Augustine’s perspectives is examined. The purpose of this study is to assert that the main and hidden reason for the existence of evil cannot be justified and understood and as Hick notes, we should confess that the world of being in general and evil in particular are mysterious.