79 Developing further what the Magisterium before me has taught, I intend in this final section to point out certain requirements which theology—and more fundamentally still, the word of God itself—makes today of philosophical thinking and contemporary philosophies. As I have already noted, philosophy must obey its own rules and be based upon its own principles; truth, however, can only be one. The content of Revelation can never debase the discoveries and legitimate autonomy of reason. Yet, conscious that it cannot set itself up as an absolute and exclusive value, reason on its part must never lose its capacity to question and to be questioned. By virtue of the splendour emanating from subsistent Being itself, revealed truth offers the fullness of light and will therefore illumine the path of philosophical enquiry. In short, Christian Revelation becomes the true point of encounter and engagement between philosophical and theological thinking in their reciprocal relationship. It is to be hoped therefore that theologians and philosophers will let themselves be guided by the authority of truth alone so that there will emerge a philosophy consonant with the word of God. Such a philosophy will be a place where Christian faith and human cultures may meet, a point of understanding between believer and non-believer. It will help lead believers to a stronger conviction that faith grows deeper and more authentic when it is wedded to thought and does not reject it. It is again the Fathers who teach us this: “To believe is nothing other than to think with assent... Believers are also thinkers: in believing, they think and in thinking, they believe... If faith does not think, it is nothing”. And again: “If there is no assent, there is no faith, for without assent one does not really believe”.
Source: Fides et Ratio (Vatican.va)