Comparison with earlier doctrine
Fides et ratio travels in the wake of magisterial statements on faith and reason over the previous century and a half. Following numerous papal Briefs and encyclicals about these topics, in 1870 Vatican I devoted a whole constitution, Dei Filius, to faith and reason. In 1879, Pope Leo XIII issued Aeterni Patris: On the Restoration of Christian Philosophy, which exhorted Christians to learn how to harmonize faith and reason from Thomas Aquinas. Fides et ratio is similar to Dei Filius and Aeterni Patris in many ways. Like Dei Filius, it claims we can know God from nature. Following its predecessors, its stresses the ‘unity of truth’, that is, that the ‘two modes of knowledge’ of faith and reason balance each other and cannot contradict one another.   In line with its precedent, Fides et ratio foregrounds the importance of metaphysics.
There are also new emphases, perhaps amounting to a development of doctrine. The earlier magisterial teachings had observed the negative features of modern philosophies. Fides et ratio does that too, but it also notes, ‘Modern philosophy clearly has the great merit of focusing attention upon man’.10 * For this encyclical, the basic human question is ‘Who am I?’ Here it mentions the Delphic Oracle with its injunction ‘Know Thyself’.
The personalist or existential understanding of human reason and philosophy in this encyclical builds on the Second Vatican Council (1962-1965). The Vatican II Constitution Gaudium et spes is the link between the earlier magisterial teaching and Fides et ratio. As the young bishop of Krakow, John Paul II (then Karol Wojtyla) was one of the authors of Gaudium et spes. This Constitution states that ‘only in the mystery of the incarnate Word does the mystery of man take on light ... Christ, the final Adam, by the revelation of the mystery of the Father and His love, fully reveals man to man himself and makes his supreme calling clear’.11 This principle, that Christ ‘fully reveals’ humanity to itself, is at the heart of Fides et ratio. Gaudium et spes talks about human beings in their concrete historical relationship to the final end of their desires and hopes, Jesus Christ. Like Gaudium et spes, Fides et ratio observes how sin darkens what should be the translucent appearance of God in the cosmos: that is, it takes the historicity of reason (its historical, post-lapsarian situation) seriously.
Fides et ratio develops the core principles of Gaudium et spes and earlier magisterial teaching towards a phenomenological understanding of the goal of human knowledge. Both faith and reason, as it understands them, are keyed towards understanding human experiences. Fides et ratio commends non-Catholic thinkers such as Jean Paul Sartre for his ‘penetrating analyses of perception and experience,
THE PHENOMENOLOGY OF FAITH: FIDES ET RATIO 147
of the imaginary and the unconscious’. It doffs its tiara to the Catholic existentialist philosopher Martin Heidegger when it notes that the ‘theme of death ... can become for all thinkers an incisive appeal to seek within themselves the true meaning of their own life’. The deepest truth we seek is the truth about who we are.
In keeping with this personalist orientation, the encyclical claims that St. Thomas Aquinas should be emulated ‘not only because of what he taught but also because of the dialogue which he undertook with the Arab and Jewish thought of his time’. The Dominican Saint exercised his reason in dialogue with diverse religions and philosophies. The idea that human beings are relational is important in the encyclical. It states that belief (the human equivalent of faith) is valuable just because, unlike ‘mere evidence ... it involves an interpersonal relationship’. In belief we trust and lean on other people, something which is ‘humanly richer’ than autonomously ascertaining the validity of evidence. Since, on the one hand, every man and woman is a ‘philosopher’, a seeker after truth, and on the other, most of what we ‘know’ is gained by trusting the reports of other people, ‘the human being - the one who seeks the truth - is also the one who lives by belief. If reason rests ultimately on human beliefs, can reason and supernatural faith be at odds?
-  See the chapter on Vatican I.
-  sFides et ratio, §19.
-  Fides et ratio, §34.
-  wFides et ratio, §5.
-  “Documents of Vatican II, Pastoral Constitution on the Church in the Modern World: Gaudium et spes(1965) §22.
-  uFides et ratio, §22, Gaudium et spes, §§10, 13, 14, 15, 17.
-  Fides et ratio, §48.
-  Fides et ratio, §43.
-  Fides et ratio, §32.