attenuation

I was looking around at the boards, and I was under the impression that people use the essay to "back up" or elaborate on their activity list in their applications. Some also use this essay space to explain about some difficulty they might have experienced during their high school years, etc. ...
That's great, but what about essays that are more idea-based? For example, I have essays that basically explain my intellectual interests by linking them (they are quite different areas-- arts and sciences) together... but do not really refer to any of my extracurricular activities, or even to any of my actions. (However, they do sort of back up the fact that I AM INTERESTED in those areas that I have pursued through extracurriculars...)

I know, I've heard it before: "It's not a matter of what you write about, it's a matter of HOW you write it." True, but it's also probably true that certain overall essay topics / structures tend to be easier to write about in a way that will be more generally accepted/approved of by college admission officers.

So, do you think an idea/theory-based essay will be acceptable? Might it be disfavored?

Thank you for your help!