"But even when there is no natural physical boundary that can be viewed as defining a container, we impose boundaries -- marking off territory so that is has an inside and a bounding surface -- whether a wall, a fence, or an abstract line or plane. There are few human instincts more basic than territoriality. And such defining of a territory, putting a boundary around it, is an act of quantification. Bounded objects, whether human beings, rocks, or land areas, have sizes. This allows them to be quantified in terms of the amount of substance they contain."