As described in a previous post, the historical conversation regarding faith and learning is diverse and includes at least three different major “streams”. Augustine is an important contributor to all three streams of this conversation. In each case, he offers an influential metaphor which has proven extremely fertile in the following centuries for Christian theology.
Faith seeking understanding. In the first (apologetic) stream of the conversation Augustine introduces the famous slogan “faith seeking understanding”. Faith in this context refers to the faith of an individual person—the act of believing. The essence of his argument is that any act of understanding is also conjoined with an act of believing. “Faith gives the understanding access to these things, unbelief closes the door to them.” (Ep. CXXXVII) A person who believes, or is willing to believe can see and understand things that are closed off from the person who refuses to believe.
So Augustine believes that our cognitive psychology is such that, at least in some cases, one must believe in order to understand something. But this is not always the case. As he puts it, “For there are some things which we do not believe unless we understand them, and there are other things which we do not understand unless we believe them.” (In Ps. CXVIII) The exact priority of faith and understanding seems to defy simple analysis for Augustine, but what is important here is to observe that these two poles are not opposed to one another but rather they operate in a deeply synergistic way. Faith is not opposed to understanding, nor is it independent of understanding. They must operate together in a well-formed human being. This is somewhat of a theme in Augustine’s writing:
Therefore, beloved, this opponent I have set up against myself…does not say nothing when he says, ‘I would understand in order that I may believe.’ Certainly what I am now saying, I say with the object that those may believe who do not yet believe. Nevertheless, unless they understand what I am saying, they cannot believe. Consequently what he says is in some part true. I would understand in order that I may believe.’ ‘Nay, believe, that you may understand.’ Accordingly, we agree, ‘Understand that you may believe, believe that you may understand.’ Sermons xliii, 9,
“… Unless he understand somewhat, no man can believe in God; nevertheless by the very faith whereby he believes, he is helped to the understanding of greater things. For there are some things which we do not believe unless we understand them, and there are other things which we do not understand unless we believe them.” (In Ps. CXVIII)
“It is seen as reasonable that faith should precede reason.” (Ep. CXX) (I believe this is Letter CXX to Consentius)
Israel plundering Egypt: When he turns his attention to the second (epistemological) stream of the conversation, he is no longer addressing the dynbamic tension between faith and understanding. Instead, his attention turns to the relationship between faith and philosophy—a tension that is played out at in broader public conversation instead of at the level of personal belief. It should be noted that “faith and understanding” and “faith and philosophy” sound more similar than they are. First, the meaning of faith is quite different, referring in this second context to the essential teachings of the Christian faith—the content of the Gospel rather than an individual’s response to that content. And the other pole, philosophy, represents a similar turn from “understanding” in that philosophy refers to a body of knowledge as opposed to individual cognition. Perhaps his most notable turn of phrase, however, is his change of metaphors. Augustine follows Origen in likening the Christian use of pagan philosophy to Israel plundering the Egyptians:
Moreover, if those who are called philosophers, and especially the Platonists, have said aught that is true and in harmony with our faith, we are not only not to shrink from it, but to claim it for our own use from those who have unlawful possession of it. For, as the Egyptians had not only the idols and heavy burdens which the people of Israel hated and fled from, but also vessels and ornaments of gold and silver…which the same people when going out of Egypt appropriated to themselves, …in the same way all branches of heathen learning have not only false and superstitious fancies and heavy burdens of unnecessary toil… but they contain also liberal instruction which is better adapted to the use of the truth, and some most excellent precepts of morality; and some truths in regard even to the worship of the One God are found among them. Now these are, so to speak, their gold and silver, which they did not create themselves, but dug out of the mines of God’s providence which are everywhere scattered abroad, and are perversely and unlawfully prostituting to the worship of devils. These, therefore, the Christian…ought to take away from them, and to devote to their proper use in preaching the gospel.
Contemporary discussions of science and religion commonly view this as an alternative formulation of the handmaiden metaphor: philosophy serving as the handmaiden of theology. Indeed, many would consider Augustine to give the most enduring formulation of the handmaiden metaphor which dates back to at least Clement of Alexandria. His approach certainly continues Clement’s idea of philosophy serving theology, but Augustine is less positive than Clement. In fact, at times, Augustine seems to almost completely dismiss the value of scientific knowledge: “Such subjects are of no profit for those who seek eternal happiness, and, what is worse, they take up very precious time that ought to be given to what is spiritually beneficial.” However, these limitations not withstanding, Augustine is clearly committed to finding and using truth wherever it may be found. As Lindberg notes, for Augustine, “Natural philosophy, pagan in origin, is legitimized— indeed, sanctified—by the service it performs for the faith…The natural sciences must be pressed into service as the handmaidens of theology and religion.”
Heavenly City and the Earthly City. Concerning the third stream of the conversation, Augustine’s City of God tells the entire story of human history as a conflict between a heavenly city and an earthly city—each defined by their respective loves—the love of God and the love of self. This account of history and society has become one of the great images of Western culture. Perhaps most important for present concerns is the underlying presupposition of conflict between the two cities. This is the conflict Tertullian felt so strongly when he asked what Athens has to do with Jerusalem, and which generally sits behind antithetical characterizations of church and world. Perhaps the ascendancy of Christian culture pushed such thinking into the background through the Middle Ages, but it has certainly reemerged in the church’s conflict with modernism. And in this regard, particularly some strands of Dutch neo-Calvinism continue this antithetical approach in their contributions to the second (epistemological stream) stream conversations regarding faith and learning in the contemporary academy.
 Augustine’s formulation influenced Anselm’s apologetic writings. His ontological argument comes to us in works entitled the Monologion and the Proslogion. But his own introduction to the work notes that: “the original title of the Monologion was “An example of meditating about the rational basis of faith”, and the original title of Proslogion was “Faith seeking understanding”.
Philip. Schaff, The Nicene and Post-Nicene Fathers Vol. II (Oak Harbor: Logos Research Systems, 1997), ECF 220.127.116.11.2.40.—On Christian Doctrine, II.40
 See for example David Lindberg, “The Medieval Church Encounters the Classical Tradition: Saint Augustine, Roger Bacon and the Handmaiden Metaphor,” in When Science and Christianity Meet, ed. David Lindberg and Ronald Numbers (Chicago: University of Chicago Press, 2003), 15-19. and Edward Grant, Science and Religion, 400 B.C. To A.D. 1550: From Aristotle to Copernicus (Westport, Conn: Greenwood Press, 2004), 112-14.
 Lindberg, “The Medieval Church Encounters the Classical Tradition: Saint Augustine, Roger Bacon and the Handmaiden Metaphor,” 14 citing Augustine’s Literal Commentary on Genesis.
 Ibid., 15.