The words "a volume of space" or, in the context of this discussion and topic, "a universe", define a volume of space, and they imply the existence of a geometrical framework consisting of four equidistant points. We could assign to this complex of points some externally derived unit of measure, but the system is self contained, or requires only the singular externally derived unit of measure, 1. We can now locate a fifth point, and any number of additional points, relative to the original four, by specifying, for each, its distance from each of the original four, using a multiple of the number 1.
In some sense lines are completely irrelevant. Points are required to define things, and lines are things, but our ultimate purpose is to derive imagery from our model. Viewed from any angle, lines are infinitely thin, and are thus invisible. Only surfaces are visible. In order to describe things that can manifest visually, we must define surfaces.
A point and a unit of distance can define a sphere, which is one kind of surface. Two points and a unit of distance can define certain other kinds of surfaces. And three points not on a line define a surface. These could be called the fundamentals of things in CAD.
