The Peripatetics used to distinguish various kinds of motion corresponding to the variety of changes which a thing could undergo. To-day those who discuss motion understand by the term only local motion. But local motion cannot be understood without understanding the meaning of locus. Now locus is defined by moderns as "the part of space which a body occupies," whence it is divided into relative and absolute corresponding to space. For they distinguish between absolute or true space and relative or apparent space. That is they postulate space on all sides measureless, immoveable, insensible, permeating and containing all bodies, which they call absolute space. But space comprehended or defined by bodies, and therefore an object of sense, is called relative, apparent, vulgar space.