As far as having a "purpose", I suppose its purpose is to distinguish one physical entity from another.
Topology - well, actually the theory of metric spaces - has a very exact way to define the "outside" of something. Basically, imagine a ball surrounding any point in or on the brick. If, no matter how small the ball is, it contains both brick and non-brick components, then the point is on the "outside" of the brick.
This won't work exactly for physical objects, though; at sufficiently small distances you may not be able to tell what sort of components, if any, the imaginary ball contains. But is there something similar one can devise?
I suppose my point is that I'm sure we *do* have words to distinguish inside from outside quite exactly - I'm just trying to find them. |
