In Christianity Saint Thomas Aquinas joined philosophy and theology, and today Catholics still feel that these separate roads to knowledge compliment each other.
The relationship between faith and reason was proclaimed in the first Vatican council:
First, reason alone is not sufficient to guide men: they need Revelation; we must carefully distinguish the truths known by reason from higher truths (mysteries) known by Revelation.
Secondly, reason and Revelation, though distinct, are not opposed to each other.
Thirdly, faith preserves reason from error; reason should do service in the cause of faith.
Fourthly, this service is rendered in three ways:
reason should prepare the minds of men to receive the Faith by proving the truths which faith presupposes (praeambula fidei);
reason should explain and develop the truths of Faith and should propose them in scientific form;
reason should defend the truths revealed by Almighty God.
The church always seems touchy about this relationship - declaring in the second proclamation and revelation are NOT opposed to each other.
Here's Pope John Paul II's letter to the Bishops on the relationship between faith and reason.
n the wake of these cultural shifts, some philosophers have abandoned the search for truth in itself and made their sole aim the attainment of a subjective certainty or a pragmatic sense of utility. This in turn has obscured the true dignity of reason, which is no longer equipped to know the truth and to seek the absolute.
48. This rapid survey of the history of philosophy, then, reveals a growing separation between faith and philosophical reason. Yet closer scrutiny shows that even in the philosophical thinking of those who helped drive faith and reason further apart there are found at times precious and seminal insights which, if pursued and developed with mind and heart rightly tuned, can lead to the discovery of truth's way. Such insights are found, for instance, in penetrating analyses of perception and experience, of the imaginary and the unconscious, of personhood and intersubjectivity, of freedom and values, of time and history. The theme of death as well can become for all thinkers an incisive appeal to seek within themselves the true meaning of their own life. But this does not mean that the link between faith and reason as it now stands does not need to be carefully examined, because each without the other is impoverished and enfeebled. Deprived of what Revelation offers, reason has taken side-tracks which expose it to the danger of losing sight of its final goal. Deprived of reason, faith has stressed feeling and experience, and so run the risk of no longer being a universal proposition. It is an illusion to think that faith, tied to weak reasoning, might be more penetrating; on the contrary, faith then runs the grave risk of withering into myth or superstition. By the same token, reason which is unrelated to an adult faith is not prompted to turn its gaze to the newness and radicality of being.
The Church hates to deny reason and science (Pope John Paul II was an evolutionist, for example) however there still needs to be room for the unreasonable in their theology. So they find ways for faith and reason to co-exist, even while tacitly acknowledging the separation between them.
I believe that these roads to knowledge can co-exist, inasmuch as philosophy and science will always have dark corners that can't be answered by reason alone. ( What came before the big bang ? And before that ? etc. )
You can see in