In his best-selling book The Reason for God, Tim Keller reflects on the substitutional atonement of Christ, pointing out that "in a real world of relationships, it is impossible to love people with a problem or a need without in some sense sharing or even changing places with them. All real life-changing love involves some form of this kind of exchange." Keller goes on to share two examples that illustrate this well. He writes:
Imagine you come into contact with a man who is innocent, but who is being hunted down by secret agents or by the government or by some other powerful group. He reaches out to you for help. If you don't help him, he will probably die, but if you ally with him, you—who were perfectly safe and secure—will be in mortal danger. This is the stuff that movie plots are made of. Again, it's him or you. He will experience increased safety and security through your involvement, but only because you are willing to enter into his insecurity and vulnerability.
Consider parenting. Children come into the world in a condition of complete dependence. They cannot operate as self-sufficient, independent agents unless their parents give up much of their own independence and freedom for years. If you don't allow your children to hinder your freedom in work and play at all, and if you only get to your children when it doesn't inconvenience you, your children will grow up physically only. In all sorts of other ways they will remain emotionally needy, troubled, and overdependent. The choice is clear. You can either sacrifice your freedom or theirs. It's them or you. To love your child well, you must decrease that they may increase. You must be willing to enter into the dependency they have so eventually they can experience the freedom and independence you have.
Keller closes with these words:
All life-changing love toward people with serious needs is a substitutional sacrifice. If you become personally involved with them, in some way, their weaknesses flow toward you as your strengths flow toward them ….
How can God be a God of love if he does not become personally involved in suffering the same violence, oppression, grief, weakness, and pain that we experience? The answer to that question is twofold: First, God can't. Second, only one major religion even claims that God does.