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Yes, that's an understandable reaction to the phrase. The quick response is that the post-avant refers to poetry (and other arts) that are working past the realisation that what were deliberately transgressive "avant-garde" activities are now totally accepted and encouraged by critical, academic and funding institutions. (Visualise Damien Hirst and his income; any art college degree show; etc). So any art which wants to still, ah blest impulses! do something actually new, and to challenge and redefine the nature of art (or poetry or whatever) has to begin to play some pretty subtle cute games that go beyond — but can make use of all of — previous avant-garde practices.
In terms of poetry, by my reckoning the term post-avant, if it's to be useful, explores the authorship, coherence, performance of the text (or indeed what text?), and happily uses (look, they're not shocking, they're our inheritance now) any of the ways poetry has innovated in the last century (or past five hundred years). So, yes, it's a continuance of that avant-garde or modernist impulse, but one that is aware there isn't going to be a revolutionary artistic utopia nor a wonderful movement to always better and more modern stuff — there's only coping with the shit we're in, the complicated inescapable language shit we're totally in. Disabused, but not disabled, and abusive yet.
For far more detail, with lengthy quotations, footnotes, the lot — go to the next page.
