It is to the prodigals … that the memory of their Father's house comes back. If the son had lived economically he would never have thought of returning.
—Simone Weil

During a British conference on comparative religions, experts from around the world were discussing whether any one belief was unique to the Christian faith. They began eliminating possibilities. Incarnation? Other religions had different versions of gods appearing in human form. Resurrection? Again, other religions had accounts of return from death. The debate went on for some time until C. S. Lewis wandered into the room. "What's the rumpus about?" he asked, and heard in reply that his colleagues were discussing Christianity's unique contribution among world religions. In his forthright manner Lewis responded, "Oh, that's easy. It's grace."

After some discussion, the conferees had to agree. The notion of God's love coming to us free of charge, no strings attached, seems to go against every instinct of humanity. The Buddhist eightfold path, the Hindu doctrine of karma, the Jewish covenant, and the Muslim code of law—each of these offers a way to earn approval. Only Christianity dares to make God's love unconditional.

Aware of our inbuilt resistance to grace, Jesus talked about it often. He described a world suffused with God's grace: where the sun shines and rain falls on people good and bad; where birds gather seeds gratis, neither plowing nor harvesting to earn them; where untended wildflowers burst into life on the hillsides. Like a visitor from a foreign country who notices what the natives overlook, Jesus saw grace everywhere. Yet he never analyzed or defined grace, and he almost never used the word. Instead, he communicated grace through ...