From his book, A Faith Of Your Own:
A God who is completely loving, powerful, and just would eliminate evil. The continued presence of evil means that God is limited in one of those three attributes… [I believe] that God is altogether loving and altogether just, but not altogether powerful. However, God is not powerless… God does not have power to control evil. Indeed, God acts not through unilateral exercise of force but through lure or persuasion. God is present in every situation seeking to lure people to the good… Moral evil results from people not responding to the lure of God toward love and justice. Even though God does not desire sickness or evil in nature, God cannot directly control such things… [I believe] every entity is living. The table on which I am writing this book may appear to be inanimate, but it is made up of atoms that are in constant motion. It is constantly in process and can respond to stimuli. Every entity in the world has freedom. Some entities — such as human beings — have high degrees of consciousness, while others — such as animals, the clouds, and this table — have lower and lower degrees of consciousness. Nevertheless, they are all alive and can respond positively or negatively to the lure toward a world of love and justice. Natural evil results from elements of creation exercising their freedom in ways that are destructive.
Tsunami cells and cancer cells act as they do because they have freedom, just as human beings have freedom to act as they do for good or for ill, and the Creator cannot remove freedom for that would remove possibilities in the universe for love, spontaneity, novelty, and joy.