In assessing the status of words in a WP model, it is worth bearing in mind the essentially utilitarian view articulated by Robins (1959):
In many ways, and quite apart from any phonological markers, the word is a unique entity in grammar, and not just a stage in the progression ‘from morpheme to utterance’. As a grammatical element the word is unique in its relative fixity of internal morphemic structure, its focal status in relation to syntactically relevant categories, and, in inflected words, the stability of its paradigms. All of these factors make it a strong basis for grammatical description, both morphological and syntactic. The assumption of a simple ascent in order of size from single morpheme to complete sentence, ignoring or blurring the distinction of morphological structuring and syntactic structuring, achieves its apparent simplicity at the cost of neglecting or distorting patent structural features of languages. (Robins 1959:137)
Word-based analyses confront genuine challenges in demarcating word forms, in determining their grammatical properties, in assigning them to larger form classes and in establishing the structure of those classes. But these are the kinds of descriptive issues that arise on any explicit grammatical analysis and, as the discussion of morphemic models in Chapter 2 suggests, few if any of these tasks are facilitated by a shift in focus to units smaller than words.