Let's, for the purpose of our work in CAD, define a universe as an expanse of space described in a file. A file is a string of bits with a name, so we can ask a computer to access the file named such and such, and it will retrieve the string of bits named such and such, if there is, in its memory, a string of bits with that name. Now we need to discuss how an expanse of space is described using a string of bits.
Let us consider the possibility of two kinds of universes, or expanses of space, empty ones, and ones that are populated by something, or some things. We now must ask, what is a thing? There are several kinds of things, namely, at least to begin, points, lines, surfaces, and solids. The relationship between solids and surfaces and lines is characterized by some interesting ambiguity, but all are defined by points.
Point are things. They are locations. The question is, relative to what?
