The idea that while there is a qualitative distinction between linguistic units encoded by open class forms and closed class forms respectively, there is not a principled distinction between the two. In other words, in cognitive linguistics it is assumed that 'lexical' and 'grammatical' units are both inherently meaningful, a consequence of the symbolic thesis. From this perspective, there is no principled distinction between a mental lexicon and a syntax component. Rather, lexical items and grammatical elements are conceived as forming a continuum.