This thesis examines Leibniz's Theodicy and its problem: how the existence of evil can be reconciled with the perfection of God. It explores the interrelation of metaphysical, physical, and moral evil with divine goodness, omnipotence, omniscience, and providence. The thesis pays attention to the theory of possible worlds and to Leibniz's claim that God chose the best among all possible worlds. The thesis also analyzes the relationship between divine foreknowledge and freedom, focusing on the distinction between certainty and necessity, as well as determination and coercion. According to Leibniz, actions may remain free despite having determining reasons, provided that they arise from the agent's will and inner motivations. The study concludes that Leibniz's system offers a coherent attempt to preserve divine goodness, responsibility, and providence simultaneously. Nevertheless, it does not resolve the problem of suffering. The Theodicy reformulates the problem of evil and reveals the limits of philosophical human understanding.