John Paul acknowledges that everyone suffers, and suffering is an evil because it diminishes physical and psychological well-being. It can also be spiritually destructive, leading as it does to doubt the existence of God. Why would a good and loving God allow pain in his world? It’s a question as old as Job.
The pope’s answer is elegantly simple. As members of the mystical body, all Christians are grafted into Christ. We share, as it were, his spiritual DNA, enjoying an indissoluble link with him shared by our brothers and sisters. We know, by faith, that Christ’s suffering was redemptive. Consequently, because we’re joined to him and to all humankind, our suffering must somehow participate in his act of redemption as well.
—from the book John Paul II: A Short Biography by Kerry Walters