Extension, Meaning, Ordinality

Like Descartes, Russell problematically relies on an hypostasization of the process connoted by 'extend'.  In his case, the abstraction is effected in his Semantic Theory, according to which the 'extension' of a concept is all its exemplifications.  Thus, for example, the 'extension' of '3' is the set of all triples.  Common to the two uses of the term is an ambition to retain the priority of the Unextended over the Extended, e. g. Mind over Body, Number over Manifold, while preserving their simultaneity, without which their segregation is difficult to maintain.  Also common to the two is a contrast with a better-grounded use elsewhere in the system--Descartes' implicitly ordinal Geometric Space, and Russell's ordinal generation, via his Successor Function, of Numbers, each of which of which is more literally 'extensive'.