100 More than a hundred years after the appearance of Pope Leo XIII's Encyclical Æterni Patris , to which I have often referred in these pages, I have sensed the need to revisit in a more systematic way the issue of the relationship between faith and philosophy. The importance of philosophical thought in the development of culture and its influence on patterns of personal and social behaviour is there for all to see. In addition, philosophy exercises a powerful, though not always obvious, influence on theology and its disciplines. For these reasons, I have judged it appropriate and necessary to emphasize the value of philosophy for the understanding of the faith, as well as the limits which philosophy faces when it neglects or rejects the truths of Revelation. The Church remains profoundly convinced that faith and reason “mutually support each other”; each influences the other, as they offer to each other a purifying critique and a stimulus to pursue the search for deeper understanding.
Source: Fides et Ratio (Vatican.va)