In the beginning God created the heavens and the earth. This world which he created currently has much evil in it. The question is why? Most responses try to show how the evil might be permitted for the sake of some good which either results in it or from it while being unobtainable otherwise.
God created the world for the sake of his glory. Further, I believe that he governs the world sovereignly. Therefore all that occurs in the world is meant by God for his glory. Romans 8:28 "And we know that for those who love God all things work together for good, for those who are called according to his purpose." This places the problem of evil in the strongest light: evil exists, yet all that happens happens to the glory of God. How can this be?
There are two kinds of evil: natural evil, as in natural disasters, and moral evil, as in the evil actions of moral agents. The first can be explained as God's punishment for sin. Since no one is innocent, but all are sinners and therefore worthy of death, when bad happens to us we are only getting what we deserve. When we escape bad happening to us it is God's grace to us.
The latter kind of evil is harder to explain. If God is in control of all that happens, then that includes our actions. How can a good God will that we sin? First, we must note that it is possible for us to will something for evil, i.e., with evil intent, while God wills it for good, i.e., for his glory. Genesis 50:20 "As for you, you meant evil against me, but God meant it for good, to
bring it about that many people should be kept alive, as they are today." The question is only how God gets glory from evil actions.
God gets glory from our evil actions in at least two ways. First, for those who remain apart from him, he shows his righteousness and justice on them by punishing them. Second, for those who repent, he shows how great his mercy and grace are to those whom he loves, whom he has called. This is an exhibition of his holiness greater than would be possible if there were no sin.
This explains how there can be sin, but it does not explain why there is so much sin. To answer that question, we may note, first, that by allowing the full extent of our depravity, the full extent of what we will tend to do apart from him, he shows how good and necessary he is for us to live as we were made to live. Secondly, by letting our evil be shown in diverse ways in various times he warns us of our evil and exhibits our own evil to us, in order that we might repent, and in order that we might recognize our need for his righteousness to work in our lives. Thirdly, we are punished for our rejection of God by the moral evil of those around us, as when the Israelites were punished by God sending foreign nations to conquer them.
In addition to these reasons why we might expect evil to be as great as it is, and why evil actually serves to glorify God, and so is involved in countering itself, we may note that the cross of Christ is a place where evil is directly confronted as evil. Our answer to the problem of evil is twofold: that it has been conquered in Christ's death, and that it is being turned to good. We, then, as the body of Christ, must be involved in the task of bringing the kingdom of God to earth in this way: combating sin and death by the power of Christ who defeated both sin and death once and for all.
Any answer to the problem of evil will imply a response to evil. The ultimate response to the problem of evil was Christ's death on the cross in which God's justice and grace were shown together. This is where we must go in responding to evil. God's justice is shown in it, and so is his grace, and in Christ God is reconciling all things to himself. We, because we are joined to Christ in his life and death, are joined to Christ in his defeat of sin and death. In light of that, we should live lives which redeem the evil in our lives by showing the power of God in our weakness.