The freewill defense goes back all the way to Augustine in the 5th century. The idea is that God wanted there to be creatures with freewill. He wanted to make creatures in his own image. An important part of that image – one of several different parts – was that human beings should be free. They should be free to respond to God, but also free to reject God. They should be free to do what is right, but also free to do what is wrong. Of course God can make free creatures, but he cannot make free creatures and also cause them to do only what is right. If he does cause them to do only what is right, then they do not do what is right freely. So some suggest that part of the reason there is evil is because God created free creatures, and these free creatures did what was wrong. It was not within God’s power to make free creatures who cannot go wrong or who he guarantees will not go wrong. He made free creatures, and they did go wrong. But the inclusion of incarnation and atonement – the great history of God being willing to suffer and die on our account – means that the world taken overall is a very good world and probably a better world than if there were free creatures who never did go wrong. In fact, in the Catholic liturgy for the Saturday night Easter vigil, there is the line “oh happy sin that occasions such a great salvation.” That is one way to think about the matter.
We do consider that God wanted to create a really good world and had all other possible worlds that he could have created instead, as opposed to the one that he did create. Why did he pick this one? What would make one world better than another? What would be ‘great-making properties’ or ‘good-making properties’ of possible worlds? There are various things you can propose. Some suggest that many people who are enjoying great happiness and enjoying good lives is a ‘great-making property’. But what the Christian story says is as great a ‘great-making property’ as any, and maybe is the very greatest one. It is the idea of creatures who have turned their backs on God, rebelled against him, paid no attention to him, and turned away from him; and in order to make it possible for them to live eternally in fellowship with him, the first being in the whole universe – God himself – was willing to have his son become human incarnate and die just on our account. It is often called ‘the greatest story ever told.’ I am inclined to say it is the greatest story that ever could be told. We think about all these different possible worlds and ‘great-making properties.’ Maybe the greatest ‘great-making property’ is a world in which incarnation and atonement happen. Of course any world with incarnation and atonement is a world with sin, evil, and suffering. If God wanted to have a really good world, he would create one containing incarnation and atonement, and also then sin and the consequent suffering.