Peter Leithart has some great thoughts on why philosophy must become theological in order to truly fulfill its purpose (the link is here). His argument hinges on the givenness of reality: our lives depend on having received, as little children, things which neither earned nor could have ever provided for ourselves, including not just our physical being but also our language, culture, and ability to reason. For all of this, the fitting response is gratitude--and not only for what we received from our parents, but even for the world itself, for the existence of anything at all. And if gratitude is the fitting response, then to whom or what are we to be grateful?
But let's consider another question: how does one arrive at this realization (namely, that gratitude is the fitting response to our own existence)? As I observe little children, one thing I notice is decidedly lacking is gratitude. It is a tad ironic that during the time when we ought to be most grateful, because we are so helpless by ourselves, we are in fact least grateful. Indeed, gratitude in little children has to be taught; it almost never comes spontaneously.
When is it that spontaneous gratitude emerges? I submit that it is precisely when one experiences loss. This experience can either be personal, as when we endure suffering ourselves, or it can be vicarious, as when we see how others live in far worse circumstances than our own. It is only when we see that what we have cannot be taken for granted that we feel the spontaneous desire to express gratitude.
I would say that the experience of loss is the beginning of philosophy. To put it more starkly, I would say death is the impetus for true philosophy. To realize that we are mortal, that our very existence cannot be taken for granted, causes us to face the most fundamental struggle in human existence: the struggle between gratitude for the life we have and despair over its loss.
Which brings me to something I would add to Leithart's post. Philosophy can either be a eucharistic enterprise, or it can be a process of despair. It can either be a response of gratitude and longing, or it can be a response of defiance, sadness, cynicism, callousness--all of which are really different sides of despair. When philosophy fails to be theological, it is because despair has won out over gratitude.
The modern world, it seems to me, is largely a world shaped by a philosophy of despair, leading to a world of non-philosophers--that is, a world of children who take what they have for granted, and never bother to face their own mortality. It's hard to be philosophical when you're just so damn successful.
But that, of course, is just part of the story. Let's not act like modern philosophy begins with atheistic "presuppositions." No, the battle is not with presuppositions of the mind but with different sides of the human heart. We are all atheists, because we all know despair. And we are all believers, because we all know gratitude--transcendent gratitude, thankfulness just to be alive. The real enemy of philosophy is not atheism, but childishness, which is to say our unwillingness to confront death and to wrestle with gratitude and despair.
No one can remain a child forever. Even we modern people must eventually be theologians.