To solve the logical impossibility to hold as true the existence of a good, omnipotent God and the presence of evil, the Leibnizian concept about the best possible world is analyzed initially. With such a notion, it is argued that great goods depend on the necessary possibility of moral evil, foreseen by God from the region of eternal truths and, without which, would be impossible the complete composition of the most perfect world. Controversial idea, when it is thought about the existence of other worlds, and even in a world where men would act good only. Secondly, it is studied the notion of freedom linked to free will, apparently contradictory when Leibniz admits the futurition of human actions. However, leaning on the terms of contingency and necessity, achieve to jump from an absolute determinism to a free determinism, saving human freedom and divine omniscience. Finally, the culpability of man in the perpetration of evil is evidenced, due to the needs that arise from his limits, in which case God remains exempted from being responsible, even when is the source of his permission and the cause of the limitations.