One of the great questions asked by people in response to Christian claims is ‘why does evil exist if God is all good?’ This is the problem of theodicy.
I believe that the best explanation for the existence of evil, of pain and of suffering is found in the purposes of God and human freedom.
Evil exists for humanity to know and choose between good or evil. Central to God’s purposes is his desire for humanity to freely choose to accept him. Because of his love for humanity, he does not impose himself upon humanity, but wants humanity to freely come to him in relationship.
This desire for freedom and choice requires the existence of both good and evil. That being the case, God allowed evil to exist to ensure that humanity throughout its history, had a clear and ongoing choice to make between good and evil. Hence we see evil’s first appearance in the garden in the form of a snake (Gen 3:1). The snake offered Adam and Eve and alternative to the command of God (Gen 3:2-5).
The event of Adam and Eve's rejection of God is the Fall when humanity fell from their place of privilege and relationship with God. The event did not merely affect humanity but saw all of creation broken and fallen; this is the reason for natural disasters which are a distortion of the good order of creation. It also saw human relationships broken, our relationship with creation violated and our own psychological make-up marred.
Throughout the history of humanity the great adversary of God is Satan and he is the anti-god and anti-good God allows to exist, so that good is understood and revealed. Just as white is only recognisable in the presence of other colours, good is only visible where evil exists in whatever shade. Freedom, good and choice can exist without the existence of evil, but require the existence of evil to become evident.
Evil exists because humanity choose it. Since the days of Adam and Eve and their choice to do evil and not good, evil continues to exist because humanity continue to choose to do evil. In fact, human history, observation and the bible’s teaching all agree that the problem with the world is evil and in particular human evil. Indeed this is the problem of the world = sin. As it says in both Old and New Testaments, all sin and fall short of God’s glory (1 Kgs 8:46; Rom 3:23).
Evil exists but will be exterminated in its time (Mt 25:41; Rev 20). When evil was accepted by humanity God allowed death and mortality to take over humanity. Wherever a human chose to do evil God could not allow them to live forever otherwise evil would live forever. Hence we all die (Rom 5:12; 6:23). Where a person could live an unblemished life, continually and without compromise choosing good over evil, they would defeat death and evil (Heb 4:15). This is what Jesus did and so he rose from the dead, vindicated by God for his perfect life.
The bible teaches that the time will come when all evil will be exterminated. This means that all beings who have chosen evil will be destroyed. The wonder of the crucifixion of Jesus is that his perfect life meant that he defeated death. The way we can defeat death and evil is not through a perfect life which is impossible for us, but through faith in Jesus. His death then becomes our death and the evil we have committed is destroyed in his death retrospectively (Rom 6:1-4; Gal 2:20; Eph 2:4-7). We then pass through death to life free of evil not because we have never committed evil but because we have expressed deep remorse and accepted his death and resurrection as our own. All who reject God and Christ will not be saved but will suffer eternally!
I conclude then that evil has been allowed its existence in the short term to assist in giving God’s created volitional beings on earth the opportunity to make their decision to accept or reject God. Evil then is very much subordinate to God and only exists to allow people choice. All evil will ultimately be separated from God eternally. Those who prefer evil will experience that ultimate separation.