There are three essential questions about the relationship between faith and reason: Is it possible for human reason to be emancipated from the Christian faith?; Without reason, why does faith become mere superstition and meaning-less?; and: Without faith, why does autonomous reason become limited? The aim that this research proposes is the solution to such questions as presented in the literature of the German theologian Joseph Ratzinger (1927 –), written in the peri-od between 1959 and April 2005. In this research, the introductory chapter pre-sents the historical evolution of relationship between faith and reason, bringing, firstly, the term’s definition of faith and reason, presenting the encounter of Christianity with philosophy, in the history of the West, one of the main moments in which the bond between them was decisive. Afterwards, the relationship is ex-plained: in the patristic period, with Justin Martyr, Tertullian of Carthage, Origen and Augustine of Hippo; in scholasticism, with Anselm of Canterbury, Thomas Aquinas and William of Ockham; and in the modern period, Renaissance, Protestant Reformation and Enlightenment. In the following chapter, Ratzinger s thoughts on faith and reason are presented. It is perceived that it is especially against the conviction of modernity – mostly of the Enlightenment – that Ratzinger seeks to respond. His reflections are found in the following questions: would faith be a type of resignation of reason before the limits of human knowledge? Would it be an irrational concession in the face of the dangers of a merely instrumental reason? The chapter begins with a summary of Ratzinger s theological career. He defends three principles for understanding the Christian faith: first, it has a personal character; second, it is a trust that generates knowledge; thirdly, it is not knowledge (in the sense of mechanical knowledge), but confidence and joy. In the last chapter, praxis is presented as one of the di-mensions of faith, which gives it value and meaning. The current age extols practical reason; however, this is not completely new to him, as such emphasis is already found in Scripture (Galatians 5:6; James 2:17). In this chapter, the practi-cal challenges of Ratzinger s thought will be presented, about the relationship be-tween faith and reason, for the current time: there is the theological challenge, teaching the correct concept that God shapes culture, because the Christian God is personal and relates to, and Christ is the ultimate revelation of God s love; there is the ethical challenge, declaring that Christianity is not moralism; the confessional challenge, asserting that theology must have an alliance with a religious confes-sion; and finally, the political challenge, which alleges that care should be taken with faith’s politicization, since the nature of the Church s mission is spiritual, human salvation does not happen through politics, the human being is a political being, but it cannot be summarized in politics and economics and the option for the poor is real and must be emphasized, however, without forgetting that the ba-sis for such commitment comes from the gospel.