Since a point is defined as having "position but no magnitude," it follows that it would require an infinite number of points to make up a line.
Similarly a line has length, but no breadth or thickness, and it would therefore require an infinite number of lines laid side by side to make up a surface.
Again a surface has, theoretically, no thickness, and it would therefore require an infinite number of surfaces superimposed on one another to make up a solid.
We must therefore conclude, by analogy, that it would require an infinite number of solids to make up a "higher solid."
In particular, a Tesseract must be supposed to contain an infinite number of cubes, and, in general, four space must be conceived of as containing an infinite number of three spaces.
(3)
"The Boundaries of a figure in a space of any dimensionality are themselves figures in the next lower space."
Thus a Line (one space) is bounded by Points (zero space).
A surface (two space) is bounded by Lines (one space).