Sentence:  The essence of <WSD>segregationalism</WSD> lies in its initial assumption that a clear, generally valid line of demarcation can be drawn between linguistic and non-linguistic phenomena and in the consequent attempt to identify and systematise a realm of properly and purely linguistic structures and meanings independently of the actual situated practices of communicative interchange in their empirical complexity. 
Meaning of the word marked with <WSD> tags:  The stance that linguistic signs act (or approach acting) as fixed codes with invariant pairings of form and meaning.