The use [of philosophy] is authorized by what [Aquinas] likens to a miraculous change in the philosophical doctrines: ‘those who use philosophical texts in sacred teaching, by subjugating them to faith, do not mix water with wine, but turn water into wine’
The Cambridge Companion to Aquinas, edited by Norman Kretzmann and Eleonore Stump
As being a former philosophy major myself, the union between philosophy and theology has always been an unsettling pursuit. Stump and Kretzmann word it well in analyzing the concepts, persona, and writings of Thomas Aquinas. Thomas seeing philosophy and theology as inseparable, explains that philosophy is a foundation for theology, theology being the higher valued education and undertaking.
In all conclusions drawn from philosophy, theology attributes them to divine revelation. Theology, in a sense, fills in philosophy’s lacking with faith. Aquinas in one of his sermons states it this way: “Faith can do more than philosophy in much; so that if philosophy is contrary to faith, it is not to be accepted.” Thomas takes it the one step further in emphatically displaying how theology trumps philosophy – i.e. in the disagreements between philosophy and theology, faith conquers.
This is at the heart of Christian thought. We can not rely on the systems of men to discover truth, although we can certainly use them to ground our sense of understanding. We can not mix the ideologies of men with the revelation of God, but we can complete those ideologies by morphing and transforming them into divine insight. This is not to say that every thought attained through reason will be revealed as truth, but this only portrays the flaw in man’s reasoning, not reason itself. In a pure means of reason, theology and philosophy coexist in perfect unity.