In thinking about your Fall theme, I cannot help but think about the different sorts of borders among us.
What I mean is that there strikes me as being at least two sorts of borders (in a very general way). The first border is physical: the physical stuff that separates one environment from another--be it the inside of our body and the external world, or the water in our glass and the wooden table it is placed upon. The second border is more arbitrary, and I guess could be called constructed: these are the lines drawn in the grass that separate countries; the social distinctions promulgated by culture and habit that make us feel different from one another; the ideological distinctions that define a political position. The former borders are a fact. They exist and seem to generally have some sort of instrumental value. The latter borders however, seem much more to be phenomena of our society. They are the sorts of things that will be forgotten once we're all long gone.
I mention this only because I feel confident saying that these are different sorts of borders, but much less confident saying why that is the case. Certainly they are physically different, but is the phenomenon of crossing one compared to the other in fact different? What is the integral difference between stepping across a line in the sand and seeing your finger bleed from a paper cut? If these are both borders, then what does makes a thing a border? Is a border something physical, something constructed, or merely something that can be crossed.