How can one live an authentically Christian life? Although many books and articles delineate the content of the Gospel message, the form or shape of an existence based on faith has not been studied as thoroughly. To use a language correctly, it is not enough to know the vocabulary; one must have a good grasp of its grammar. This book attempts to deepen our knowledge of the grammar of the Christian life starting from the notion of metanoia. Generally translated as “repentance” or “conversion,” the word has in fact a much richer significance: it describes a total transformation of our being, never accomplished once and for all, through the action of the Spirit of the risen Christ. Metanoia takes us out of our self-centered outlook and our limited and self-interested actions and brings us into God’s today, where we become witnesses to a real Presence, that of the universal Body of Christ.