In the winter semester of 1900, the Lutheran, liberal-minded theologian Adolf von Harnack gave in sixteen lectures, at the University of Berlin, a course designed for students from all the faculties entitled ‘‘The Essence of Christianity,’’ which recalled the title of a work by Ludwig Feuerbach, published in 1841. The lectures were soon collected in a volume that became a classic of Lutheran theology, one of the cornerstones of liberal thought against which Karl Barth thundered. Where Feuerbach proved to be destructive, Harnack turned out to be reductive, subjecting God to the measure of man, who ended up taking the upper hand over God’s own holiness. Later, in the late 1920s, in Tübingen, a Catholic dogmatic theologian, Karl Adam, also gave a lecture course on the nature of Catholicism. In opposition to modernism, Adam argued that the Catholic Church is a community capable of acting and suffering, of praying and loving, of growing and preserving unity. Moreover, it has grown enormously since A.D. 33, the year of Jesus’ death, but at the same time has preserved its identity through the centuries and in those peoples where it has spread. Adam’s book, too, had a long-lasting success.
However, the author to whom Ratzinger felt closest and who inspired him was certainly Romano Guardini, who in turn published, in 1938, a book entitled the Essence of Christianity. The Italian-German author, in the initial pages, wondered: ‘‘What is the particular quality peculiar to it alone, by virtue of which Christianity is founded and is distinguished from all the other religious possibilities?’’ Guardini then rejected a wide range of false answers that ended up reducing Christianity to natural categories. The meaning of Christianity, therefore, must be derived from within, in particular from its essential core, Jesus of Nazareth. ‘‘Through the Incarnation of the Son of God, through the mystery of faith and grace, all creation is required to give up its—apparent—autonomy and to submit to the dominion of a concrete person, namely, Jesus Christ, and to make him its own fundamental norm.’’ Ratzinger’s long confrontation with Christology would show how seriously Ratzinger had taken his reading of Guardini.
In any case, lectures directed to students from all the faculties were a gigantic undertaking in theology. On the wave of the growing popularity he had among students, in the summer semester of 1967, Ratzinger in his turn ventured to offer a similar course. In response as well to the request by the council Fathers, who asked for a simple, uniform exposition of the Catholic faith, the subject was a general introduction to Christianity in the form of a commentary on the Apostles’ Creed. It was presented in the sober form that was so dear to the author, with arguments drawn from tradition and the Fathers, but also from personalist philosophy and the Hassidic tradition. Just as he transferred to Tübingen, Ratzinger changed his assistant, and, instead of Werner Böckenförde as his right-hand man, now there was Peter Kuhn, an expert in Judaic language and literature. Students from all fields attended the two weekly lectures that took place on Wednesday and Thursday afternoon, from 5:00 to 6:00 P.M., but priests assigned to pastoral work, religious, and simple lay people also attended. Faithful to his own way of writing and arguing, Ratzinger introduced into his presentation, however, a series of anecdotes that impressed the audience and contributed to the success of the initiative.
Among those who are not devoted to work, the example of Clever Hans became famous, the prototype of the theologian who is optimistic at all costs, who exchanges the truths of the faith for current opinions that are less and less convincing. In the end, like Hans, who started his trip with a load of gold that he trades for products of less and less value until he finds in his hands a whetstone that he then throws away, the theologian, too, ends up becoming a bearer of opinions that are completely useless. Another story that caused a sensation was the example of the theologian who, in order to make himself heard, changes his clothes and language, ending up in the situation of the clown that Kierkegaard had talked about in his day. Urged by a circus owner to ask for help from nearby villagers because a fire has broken out in the camp, he runs, without taking the time to change his costume. His haste, however, is not rewarded with success. When he arrives in the nearby village, his distressed pleas for help are welcomed by the loud laughter of the villagers. They think he is reciting his lines well, that his desperate attempts to urge them to action are just a trick to convince them to watch the show.
Hence Ratzinger’s conclusion: it is not enough for a theologian or a preacher to change his clothes in order to be taken seriously. In a time when the reasons for non-belief are presented and diffused with a previously unknown vigor, the theologian must rigorously dig into the grounds of his faith and present them frankly, even at the risk of being ridiculed. Besides, the abyss of doubt yawns not only in front of the believer. Even the nonbeliever must grapple with the hypothesis that God may exist, that the believer is not chasing fairy tales, but that he may have reasonable arguments at the foundation of his faith. Ratzinger made use of a Jewish story, related by Martin Buber, to suggest this idea humorously. A well-educated scholar went to visit a tzadik to cause a crisis in the latter’s convictions, to wreak havoc with his apologetics. Upon being admitted in the room of the just man, he was about to repeat his arguments, which had already caused many other learned men to question their certainties. The tzadik, however, did not seem to pay him much attention. He continued to pace back and forth in his room and only after a while glanced at him and exclaimed: ‘‘Who knows, maybe it really is true.’’ The learned scholar sought, in vain, the strength to reply. That observation: ‘‘Who knows, maybe it really is true,’’ was already making its way inside his mind.
These courageous and acute observations attracted a growing number of auditors at Ratzinger’s lectures. Peter Kuhn then had the idea of going beyond a mere transcript for the handouts and brought his huge tape recorder to the auditorium. The lectures, thus recorded, were then transcribed, and, with a few corrections, the text of the Introduction to Christianity was ready for the press. Published for the first time in 1968, the book was a dazzling success. In Germany it was reprinted a dozen times in just one year; abroad it was translated into about twenty languages. Very few books of theology can boast such a wide readership.
The Christian, a Castaway Clinging to the Cross
The examples admonishing the reader to consider the importance of theology are accompanied by a powerful exhortation to rely on faith, which, far from resulting in a protected circle or a Church outside which there is no salvation, is support for universal brotherhood. The starting point of Ratzinger’s argument is that every Christian is called to plunge into the abyss of faith, experiencing every man’s condition of poverty and indigence. ‘‘The believer is always threatened with an uncertainty that in moments of temptation can suddenly and unexpectedly cast a piercing light on the fragility of the whole that usually seems so self-evident to him.’’ Even a saint like Thérèse of Lisieux, who grew up sheltered by a faith protected by membership in a remarkable family and by the high walls of the Carmel, cannot escape, at the height of her mystical experience and her earthly journey, the ‘‘worst temptations of atheism.’’ In the uncertainty that surrounds it and threatens the foundations of its faith, the soul of the believer experiences its own extreme poverty, but also the brotherhood that creates a bond with every other human being.
In this descent into the skin of sinners and nonbelievers, the believer finds himself in the situation described by Paul Claudel at the beginning of The Satin Slipper, the work made known in Germany by Hans Urs von Balthasar, who promoted its first performance in Zurich during the war, seeing in it a clear allusion to the world situation at the time.
The beginning of the play tells the story of a Jesuit missionary whose ship has been sunk by pirates. He is adrift, clinging to a board from the sunken ship like Jesus to the Cross, but the board is not attached to anything, so that he ends up sinking in the middle of the ocean, halfway between the old and the new world. According to Ratzinger, this is the real situation in which the believer lives in our time. Only a miserable wooden board binds him to life, to God, but everything makes him think he will soon be swallowed up in the abyss, like all the other castaways from the ship. The believer, however, following the example of Saint John of the Cross or Saint Thérèse of Lisieux, does not let go of the board, knowing that it has the strength and power to bring to safety not only him but also his brother and all those who can somehow cling to it. The Jesuit Father, in fact, has a brother, Rodrigo, who is the prototype of the worldly man, an adventurer wandering between God and the world. Rather, Ratzinger continued (repeating an idea of his friend von Balthasar), the Jesuit, like every believer, clings to the Cross not only for himself but also for his brother who considers himself a nonbeliever, who has turned his back on God and, tired of waiting, employs all his energies to acquire the riches of this world. The brother can thus be saved, drawn by the power of those ropes and that unstable board. Even the nonbeliever, in reality, cannot stay compact and hermetically sealed in his non-faith, but he, too, is subject to the doubt that exposes him to the temptation to believe. ‘‘Anyone who makes up his mind to evade the uncertainty of belief will have to experience the uncertainty of unbelief, which can never finally eliminate for certain the possibility that belief may after all be the truth.’’
Ratzinger’s observation was a warning for the generation that was bound to face the tormented period of 1968. To the many who were about to leave the Church because they did not want to be members of a community that, both because of its historical past and because of some reductive theological views, seemed to exclude the poor, the weak, the damned, Ratzinger showed an inclusive brotherhood extending to all the sons of Adam.
Introduction to Christianity rightly begins with a reflection on the act of faith. Faith is the recognition that reality is more than the sense objects that we can touch and shape, more than factum, something that we can transform with our hands; it is the realization that the invisible precedes the sensible and, indeed, is more real than the visible. Moreover, faith is the confident acceptance of the meaning of what is real; it is a confident stance on the ground of the Logos, the word of God that, for Christians, is a person whose name is Jesus Christ. And not only that. As John’s Gospel says, the Word was with God and the Word was God. In the beginning, therefore, there is not an abstract thought but, rather, a relationship that, as the evangelist hastens to point out, is a relationship of love that unites the Father and the Son with one another. In love, the Father generates the Son; in love, he creates the world in the image of the Son. That is why creation is full of signs that refer to God, which mankind has recognized over the centuries and transmitted through religions.
Not only that: when confronted with man’s sin, as dramatically recorded in the Book of Genesis, Father and Son conceive their plan for redemption. The Son offers to come into the world; the Father accompanies the mission of the Son in the spirit of their common love. Thus, salvation history begins as a mystery of love with well-defined persons (Abraham, Moses) and with a people that likewise has a precise name: the sons of Jacob or Israel. God makes a covenant with this people, entrusts to it his law and his name. God then comes out of his secrecy and his fullness and reveals himself.
Ratzinger also stressed, however, the importance of negative theology, in which love prevails over knowledge:
We are now touching a realm in which any false forthrightness in the attempt to gain too precise a knowledge is bound to end in disastrous foolishness; a realm in which only the humble admission of ignorance can be true knowledge Love is always mysterium—more than one can reckon or grasp by subsequent reckoning.
The Love That Moves the Sun and the Other Stars
The second part of the book, reflection on the Son of God, is introduced by the final verse of Dante’s Comedy, ‘‘The love that moves the sun and the other stars,’’ and by the entire conclusion of canto XXXIII of the Paradiso. The mystery of God is revealed to Dante through the human figure that shines with the very hue of the circle of God (XXXIII, vv. 130–31). Moreover, not only the Trinitarian doctrine, even Christology begins with a mystery, the scandal of the historicity of the Word that comes into the world and dies in it. The theology of the Incarnation and the theology of the Cross fuse, as is again evident in the most obvious way in John’s Gospel. But this way, the meaning of everything comes to rely on a little branch that floats in the ocean of history.
To counter this objection, contemporary theologians and exegetes have ended up following the positive method of the natural sciences, which are limited to cataloguing rather than interpreting or inquiring about meaning. Yet in the field of history and that of theology, positivism creates an antithesis between meaning and history, between Logos and event, which leads to the denial of theology itself and of the reflection on God. The first step in this direction was taken by Harnack in his What Is Christianity? Harnack focused his attention on Jesus, stripping him of his supernatural revelatory attributes, which are considered later additions by the evangelists. The central statement of his work is: ‘‘Not the Son but only the Father belongs in the Gospel.’’
Ratzinger ironically commented: ‘‘How simple, how liberating this seems! . . . Jesus versus Christ, and this means ‘away from dogma, onward to love’.’’ Not only that. A few decades after the publication of Harnack’s book, the anthropological optimism that his work promoted ended up being trampled under the boots of the marching armies. Therefore, it was necessary to change direction, to escape the mirage of historicism so as to respond to the thirst for the supernatural, to the question of meaning. That is what Rudolf Bultmann did: during the years of World War II, he stated that, as far as Jesus is concerned, the important thing was that he existed; for the rest, faith was not based on such uncertain historical bases but solely on his preaching, the kerygma, contained in the Gospels. Ratzinger wondered: Once the question about Jesus and his person had been deemed irrelevant, was any progress made? Preaching is important, but it loses legitimacy and meaning when it is detached from his person. During the rest of the sixties, with the so-called ‘‘theology of the death of God,’’ there was once again an insistence on Jesus as a person: we have lost God, but we have Jesus, who is a sign of trust. ‘‘In the midst of a world emptied of God, his humanity is to be a sort of proxy for the God who can no longer be discovered.’’
For Ratzinger, however, the oscillation between Jesus and Christ that characterized the first half of the twentieth century was not in vain. It stimulated closer consideration of the good reasons behind the transformation of the title ‘‘Christ,’’ Messiah, into a proper name as we understand it. Christ is, indeed, a title that indicates a name as we understand it. Christ is, indeed, a title that indicates an office, a commission, but it is also a person, because in Jesus it is not possible to distinguish between person and office. Jesus did not accomplish a mission different from his person. Calling him Christ means affirming that he identified himself with his office, with his commission, with his word. He is the Verbum, the Word; he acts and gives himself; he is self-giving. Jesus said about his death on the Cross: ‘‘And I, when I am lifted up from the earth, will draw all men to myself’’ (Jn 12:32).
Ratzinger commented: ‘‘This sentence is intended to explain the meaning of Jesus’ death on the Cross. . . . The event of the crucifixion appears there as a process of opening, in which the scattered man-monads are drawn into the embrace of Jesus Christ, into the wide span of his outstretched arms.’’ This brings us back to the Cross again. ‘‘As the crucified criminal, this Jesus is the Christ, the King. His crucifixion is his coronation. . . . His existence is thus his word. He is word because he is love.’’ Thus we return to the Cross about which Claudel spoke in his Satin Slipper. The Jesuit, like every Christian, clings to it in faith and love. Jesus Christ, indeed, is not a wreck accidentally lost in the ocean; rather, he is a person who comes from the Father for the love of mankind. Through the Cross to which Christians adhere by faith, love is revealed, which is the nature of God, the meaning of the world and of history, the path by which every man can reach God.
The Spirit and the Church
The third part of the book and of the Creed is introduced by the statement relative to the Holy Spirit. Ratzinger hastened to make a clarification. Holy Spirit here refers, not to the third Person of the Holy Trinity in his being within the divine life, but, rather, the Spirit understood as a divine gift left by Jesus to mankind. He is ‘‘the power through which the risen Lord remains present in the history of the world as the principle of a new history and a new world.’’ In this way, the article referring to the Holy Spirit becomes interwoven with the one about the Church and her sacraments. It is what can be inferred from the following article on the communio sanctorum, which must be interpreted above all as a communion of holy things, of the Eucharist.
The other article, the one on the remission of sins, primarily concerns the first sacrament of the Christian initiation, Baptism, but soon the focus extends also to the remission of the sins of wayfarers, of those who travel through history and always need forgiveness for their faults and weaknesses. The connection between Holy Spirit and Church already partially eliminates the difficulties that emerge as soon as the Church is defined as one, holy, catholic, apostolic. The characteristics of the Church do not depend on the observance of the covenant with the Redeemer but, rather, are given by God in the form of grace that continues despite the infidelity of mankind. Lastly, the article about the resurrection of the body expresses the New Testament hope of the resurrection of the person, the unique human composition of body and soul. The fact, then, that ‘‘the awakening is expected on the ‘Last Day’, at the end of history, and in the company of all mankind indicates the communal character of human immortality, which is related to the whole of mankind.’’
 Adolf von Harnack, What Is Christianity?, trans. Thomas Bailey Saunders (New York: G. P. Putnam’s Sons, 1901).
 Karl Adam, The Spirit of Catholicism, trans. Justin McCann (Steubenville, Ohio: Franciscan University Press, 1996).
 Romano Guardini, Das Wesen des Christentums (Würzburg: Werkbund Verlag, 1938). Citations are from the Italian edition, L’essenza del cristianesimo (Brescia: Morcelliana, 2009).
 Ibid., 7.
 Ibid., 12.
 The same motivations were at the origin of the Catechism of the Catholic Church (Vatican City: Libreria Editrice Vaticana, 1992), and subsequently in the Compendium of that same catechism (Vatican City: Libreria Editrice Vaticana, 2005). Both editorial projects were directed by Ratzinger, amid the skepticism of many theologians. Its widespread circulation nevertheless proved that the project was initiated for the right reasons.
 Martin Buber, Werke (Munich: Kösel; Heidelberg: Schneider, 1963), 3:348.
 In the original German, the book was published by Kösel (Munich, 1968) with the title Einfuhrung in das Christentum.
 Ratzinger, Introduction…, op. cit., 42.
 Paul Claudel, The Satin Slipper (London: Sheed & Ward, 1945).
 Elio Guerriero, Hans Urs von Balthasar (Cinisello Balsamo: San Paolo, 1991), 86.
 Ibid., 162.
 Ibid., 199.
 Ibid., 200.
 Ibid., 239-240.
 Ibid., 206.
 Ibid., 332-333.
 Ibid., 354.