‘Losing one's faith’ usually refers to ceasing to believe in God and in doctrines. But what changes—and losses—are experienced in the moral life when there is loss of faith? With reference to Aquinas, changes in moral understanding related to the loss of faith are discussed. Next, changes in the life of virtue and so in moral knowledge are examined, and finally changes in the inner moral life—particularly, the loss of moral certainty. The paper suggests that when they experience loss of faith Christian societies can suffer the same sorts of moral losses as Christian individuals. Such loss has inevitable effects upon identity, happiness and capacity to communicate with others.