This is a great question. Let me start off with some background information.
First, John Hick is a longtime professor at the Claremount Graduate school in California. His chief works are in the area of pluralism and theodicy. He is a left leaning evangelical. For much of his academic career he wrestled with the problem of evil.
Second, he is trying to find a theological and philosophical answer to the following three statements.
- God is all powerful
- God is good.
- There is evil in the world, hence God must not be either all powerful or all good.
Hick does not claim to have answered the question to a perfect degree, but he does believe that Christianity does have a good answer. He argues that God is all powerful and good, but he allows evil in the world to mature believers. To be sure it is hard to see this, especially in times of suffering. However, our experiences are not a perfect indicator of what is ultimately happening, according to Hick.
On a more theological level, he does not interpret Genesis 3 as the fall of humanity from grace. He argues that men were created with freewill to grow. He calls this creational evolvement. All of this akin to a relationship between a parent and an child. In this sense, God uses "evil" to mature people. He follows the theology of Irenaeus, instead of Augustine.
For more information, read Evil and the Love of God, 1966.