One of the glories, as well as one of the problems, with doing dissertation reading is that it leads to yet other reading. For example, I am working on a part of my dissertation that requires me to go into some biographical data--I am trying to make the case that because certain people were famous, their decisions exerted influence on the decisions of others, which in turn helped a specific text get taken up as an important piece of work. Those who know me know which piece I'm talking about; the rest of you get to wait until the dissertation is done.
Anyway, as I have been doing the reading, I have been finding that at least one of the people I am dealing with right now ran around with some other famous people. Not being a specialist in the period where these people are situated, I was not aware of the awesomeness of those other people, and so I went to do some reading-up on them. And so, hours later, I found that I was looking at something entirely different and not really helpful for the work, but damned interesting.
I often field the question of why I study what I study. My stock answer is "the jokes," and it is not at all untrue. I like to laugh, and there is something funny about there being penis jokes in the "romantic" poems called Shakespearean sonnets or in Anglo-Saxon riddles, or even, as my graduate advisor pointed out to me, in Sir Gawain and the Green Knight (maybe I'll explain sometime). Another answer, though, and one that makes sense only to some, is that studying what I study forces me to study other things, as well, so that I end up learning quite a bit about quite a few things.
The reason I do not usually offer the second answer to people is that many of those who throw the question at me do not have a well-developed love of learning. That I would study just so that I can study confuses them, probably because they have not had much success in "learning" in other parts of their lives.
In that I have, as in a great many other things, I am fortunate, and I am thankful to be thus fortunate.