I've written on this matter before by appeal to Origen, who undoubtedly had to answer questions of this sort from people who were by far less educated than he was. He displays great erudition in his sermons and an awareness of different philosophical trends and beliefs. He knows the Greek philosophical schools, though he is not plainly faithful nor overly sympathetic to any one in particular; rather, his concern is above all to understand the revelation of God in the scriptures in harmony with Church Tradition, and he makes use of philosophy when it is helpful to this end.
In one of his homilies on Genesis, he offers an allegorical interpretation of an episode in which Isaac digs up some of his father's wells which had been filled by the Philistines. Isaac represents Christ, the wells represent the scriptures, and the Philistines are those who limit the interpretation of the scriptures only to the literal, "earthly" sense, and thus fill the wells with earth. Origen insists that, with Christ and the coming of the Holy Spiirt, the scriptures now ought also to be understood according to a deeper, spiritual meaning.
Then he considers the following potential objection from a person who is not a Christian and who takes notice of his manner of argument, his style, his rhetoric, and the rest -- all the products of pagan education:
Someone from among those who are now listening to me, one who has had a secular education, might be able to say: "What you are saying belongs to us, and the knowledge of such art is ours; even this rhetoric by which you are expounding and teaching is our rhetoric." Maybe such a person is trying to provoke an argument, like a Philistine, saying, "You are digging a well on my land!" (Hom. in Gen. XIII, §3).Origen's response is quite impressive:
I will respond to this as follows: any plot of land has water, but whoever is a Philistine, whoever tastes earthly things, doesn't know how to find water in any old plot of land; doesn't know how to find in any soul rational thought and the image of God; doesn't know that he can find faith, piety, religion in everything. What does it help you to have knowledge and not to know how to make use of it, if you have the word and don't know what to say? These things are especially the work of Isaac's servants, who dig the wells of living water in any land whatsoever: they preach the Word of God to every soul and discover fruit (ibid.).This is the fascinating aspect in what he says: faith, piety, and religion can be found in everything, even in the rhetoric and style of teaching and interpretation of the pagans. Origen's is a view of the world in which God has not been utterly removed from everything that has ever happened apart from his special interventions with the people of Israel. This is a viewpoint that some persons have, as I've shared before on my blog, but which is extreme and not worth taking seriously. On the contrary, following the general theme of Origen's theology, we might understand that God, being good, takes special providential care of people in general and of everyone in particular. He is never utterly far off and removed from a person, so as not to be accessible to him and present to him in at least some way or other. And precisely on this basis, there is something of God -- something of faith, piety, and religion -- to be found even in those places where the full revelation of God in the form of Christian faith and preaching is absent.
For this same reason, it is not useless for a Christian to study philosophy or rhetoric or whatever else. God, who cares for anyone and everyone, is not utterly removed from the philosophers. Even if they may be largely wrong, there is still a recognizable goodness and truth in at least some of what they said; and whatever is true and good ought to be celebrated wherever it is found.