All Christian theology is historical. It is rooted in history, influenced by language, culture, and story. We see this in how Plato and Greek philosophy greatly impacted the Church Fathers, Aristotle ("The Philosopher") was a key shaper of Aquinas, and Enlightenment thought made a tremendous shift in Western theology. We continue to try and grapple with what Jewish and Greek words meant in their original Biblical context, as we try to understand why that particular word was chosen and its linguistic significance for then and today. Language, concepts, and culture have a left a consistent imprint upon Christian thought.
For two of my recent classes, the textbooks have spent their first sections on this topic of Western history. They do this because history is so key for theology and the class needs a common footing. But the books also delve into Western civilization because they have to assume that the students know next to nothing of Western intellectual history. Sadly, it's true. Students seem taken aback about Modernity versus ancient times. Most of their historical notions are fairly populist: the Middle Ages were a time when the Church and the Pope were bad, and then the Protestants fixed things up, and now we can have freedom and shop when we want.
The frustrating result is instructors have to spend a third of the semester's class time on history that students should largely know. These are kids that presumably did well in high school and have gone on to college, but who live in a world of popular historical memes and notions. Rather than doing more advanced work with the material or even the history, we must cover the basics.
I know that instructors have complained about students' knowledge and preparation for centuries. What makes this generation different are the endless distractions they have available: cable television, internet, facebook, you name it. Students could always blow off their work in the past, but the threshold was higher; to go fishing you had to get your pole and worms, maybe pack a lunch. You had to walk all the way to your friend's house and then walk to town to see a movie. In today's world, many students have movies in their pockets (that is, on their iPhones) and numerous ways to contact and hang out with each other. These aren't bad things, but they are far easier and thus more seductive than they used to be. Who wants to read chapter three when you can watch Star Wars for the tenth time?
Interestingly, however, philosophy has a different relationship to history. Although a bit of history helps explain larger trends and interests among philosophers, their ideas to stand on their own more easily. One can read a dialogue by Plato and not have to know that it's from Greece, that it's 2,400 years old, or that it's pre-modern (although these things will help). Understanding that Kant is responding to Hume helps Kantian ideas make more sense, but it's not necessary; Kant can stand on his own. Philosophy's rational underpinnings really show here – the dependence on rationalism means that philosophy doesn't need history quite as intimately as theology does (that's not to say that philosophy can escape it, but that it is more independent of it). Theology is more rooted, as we've come to realize, in narrative and history, and so the Enlightenment project failed.
Lessing's ditch remains, which in the end is just fine. We ourselves are, after all, creatures of history.