Forgiveness is at the heart of the Christian faith, and this is never more apparent than during Lent. As we approach Good Friday and Easter, we necessarily reflect on the cross and its relationship to forgiveness. Jesus, we say, quoting Scripture, died for our sins, but exactly what that means can vary from tradition to tradition or, indeed, from Christian to Christian. When I was working on Making Sense of the Cross, I was struck by some of the contested views of the relationship between the cross and forgiveness. The substitutionary theory of atonement, for instance, suggests that the cross is the mechanism by which forgiveness is even...