Prospectus, Part the first

I'm beginning to try to write my prospectus. How is one meant to express in ten pages, the work one hopes to accomplish in the next two years, not knowing yet exactly where that work will take you?

I'm beginning to see that my topic is good if you take for granted the importance of my theoretical framework. If you don't, however, it looks amateurish and unacademic. So, what I need to do is demonstrate, really convincingly, that my mode of thinking is relevant and intelligent enough to merit those two years' work. Alternately, I need to find a way to conceive of my theoretical frame as a genre and undertake the project as a study of that genre. So, this is what I need to do in my introduction (of both the prospectus and the dissertation itself).

One way of establishing relevance is to illustrate my topic's historical trajectory. How far back do I reach in pursuit of this goal? Certainly back to Goethe - Die Wahlverwandtschaften is an obvious choice - but do I attempt to go further? And if I don't, do I have to come up with a rationale for starting with the Goethezeit? Is my topic a phenomenon of the Enlightenment? If it is, why am I focusing on the 20th century? Too many things to think about.