From Pope St. John Paul II’s encyclical Fides et Ratio (1984):
A second stance adopted by philosophy is often designated as Christian philosophy. In itself, the term is valid, but it should not be misunderstood: it in no way intends to suggest that there is an official philosophy of the Church, since the faith as such is not a philosophy. The term seeks rather to indicate a Christian way of philosophizing, a philosophical speculation conceived in dynamic union with faith. It does not therefore refer simply to a philosophy developed by Christian philosophers who have striven in their research not to contradict the faith. The term Christian philosophy includes those important developments of philosophical thinking which would not have happened without the direct or indirect contribution of Christian faith.
Christian philosophy therefore has two aspects. The first is subjective, in the sense that faith purifies reason. As a theological virtue, faith liberates reason from presumption, the typical temptation of the philosopher. Saint Paul, the Fathers of the Church and, closer to our own time, philosophers such as Pascal and Kierkegaard reproached such presumption. The philosopher who learns humility will also find courage to tackle questions which are difficult to resolve if the data of Revelation are ignored—for example, the problem of evil and suffering, the personal nature of God and the question of the meaning of life or, more directly, the radical metaphysical question, “Why is there something rather than nothing?”.
The second aspect of Christian philosophy is objective, in the sense that it concerns content. Revelation clearly proposes certain truths which might never have been discovered by reason unaided, although they are not of themselves inaccessible to reason. Among these truths is the notion of a free and personal God who is the Creator of the world, a truth which has been so crucial for the development of philosophical thinking, especially the philosophy of being. There is also the reality of sin, as it appears in the light of faith, which helps to shape an adequate philosophical formulation of the problem of evil. The notion of the person as a spiritual being is another of faith’s specific contributions: the Christian proclamation of human dignity, equality and freedom has undoubtedly influenced modern philosophical thought. In more recent times, there has been the discovery that history as event—so central to Christian Revelation—is important for philosophy as well. It is no accident that this has become pivotal for a philosophy of history which stakes its claim as a new chapter in the human search for truth.
Among the objective elements of Christian philosophy we might also place the need to explore the rationality of certain truths expressed in Sacred Scripture, such as the possibility of man’s supernatural vocation and original sin itself. These are tasks which challenge reason to recognize that there is something true and rational lying far beyond the straits within which it would normally be confined. These questions in fact broaden reason’s scope for action.
In speculating on these questions, philosophers have not become theologians, since they have not sought to understand and expound the truths of faith on the basis of Revelation. They have continued working on their own terrain and with their own purely rational method, yet extending their research to new aspects of truth. It could be said that a good part of modern and contemporary philosophy would not exist without this stimulus of the word of God. This conclusion retains all its relevance, despite the disappointing fact that many thinkers in recent centuries have abandoned Christian orthodoxy.
— Fides et Ratio 76