Literary language vs mother tongue?

This is the abstract of an article entitled "Mother Tongues and Literary Languages" (Modern Language Review, 2001), by Giulio Lepschy:

"This lecture examines the notion of ‘native speaker’ and ‘mother tongue’: the former acquired popularity in the early twentieth century, the latter is based on a Medieval Latin expression (lingua materna) which particularly in its German shape (Muttersprache) became central for European national movements in the eighteenth and nineteenth centuries. The implications of these notions are discussed with reference to Renaissance Latin, the revival of Hebrew, and modern Italian (particularly its twentieth-century development into a spoken language, distinct both from the dialects and from the traditional written language). Finally, the intriguing question is considered whether poets can more appropriately be said to express themselves in a native or a literary language."

Not being a subscriber to Modern Language Review (I would have to pay to read the article), I don't know how Lepschy answers the "intriguing question," but it is clear that the question is indeed intriguing.

William Wordsworth was not the first, but he was certainly the most influential poet to highlight the question by insisting that poets should write in "language really used by men." (Like poets of his time, Wordsworth did not realize that he had excluded women from the human race.) Of course, Wordsworth hedged by asking for "a certain colouring of imagination, whereby ordinary things should be presented to the mind in an unusual aspect," thus typically introducing vagueness into what would have been a categorical yes-or-no answer. If the language of poetry were a literary rather than a natural language, it would not be subject to the laws of natural language. That, indeed, would be intriguing.