Yesterday I read an article about Aldo Van Eyck's theory of threshold. He describes threshold, or in-between as "a discourse on the need for architecture to reconcile spatial polarities such as inside-outside." The article goes on to talk about a famous issue of Forum from 1960, where Van Eyck "would develop the concept that the in-between must be conceived 'in the image of man,' and that like man himself, the in-between 'must breathe both in and out.' Van Eyck writes, ' Man still breathes both in and out. When is architecture going to do the same.' The article also cites Walter Benjamin, who conceived the threshold not as a border, but a zone that can be inhabited. He called for a "'science of the threshold,' which entailed the perilous art of inhabiting limits, being acquainted with lines and settling in the borderlines."
I also read Acting in the Interstices: Thougts on an Ethic of Hybrid Identity. This passage really caught my attention. "The way is the destination; being as process - identity defines itself anew from moment to moment as the sum of all possibilities, and derives its potential from its positioning in the interstice, the gap between the Self and the Other as empty space conceived of as a setting for activity and dynamism. It is a meditative emptiness in which the Self can experience itself outside of familiar structures in the process of confronting the Other....and by recognizing this friction as the chance for development."
To me, you can switch out the terms Self and Other with inside/outside, here/there, small/large, part/whole, house/city.