Quantifying a Heart

For the second year in a row, I'm asking all of my students to develop a personal philosophy to guide their own learning this semester. They're using wikispaces to organize their ideas, to make connections to texts and to the rest of the outside world, and most importantly, to complicate their perceptions.

So here's the problem: I have no idea how to grade them. I've tried several different rubrics, and none of them have done justice to this personal project. Part of the issue is that the guidelines are loose; I give my students a basic outline, suggestions, and examples, but the rest is really up to them because I want their wikispaces to be unique, not formulaic. I don't want to "ruin" this project for them by giving them a long checklist of requirements, and I think they appreciate that. But when it comes down to making a rubric and to offering meaningful feedback, I struggle. I've tried making a list of what I'd like them to get out of this project and what they would like to get out of this project, but it always feels artificial to assign a point value to something that comes from their hearts.

Ideas?