Seamus Perry at the LRB:
It is not the critical fashion to dwell on Shelley’s Platonism, and it is true that his expressions of enthusiasm for various Platonic doctrines were qualified. But it is difficult not to see the main feeling in his work as a conviction that the world of experience is merely an imperfect clue to the real reality that lies beyond, the idea of which haunts it; and, after all, that is nothing but a Platonic notion. ‘The truth and splendour of his imagery and the melody of his language is the most intense that it is possible to conceive,’ Shelley says of Plato in his polemic A Defence of Poetry; he translated the Symposium, and once said he would rather be damned with Plato and Bacon than go to heaven with the Anglican worthies Paley and Malthus. ‘You know that I always seek in what I see the manifestation of something beyond the present & tangible object,’ he told a correspondent: there is ‘no more fitting epigraph to the dynamic driving Shelley’s literary career’, according to the poet and critic Michael O’Neill, one of our best Shelleyan commentators. The ghostly effects that this penchant for intangibility enables in his poetry – its distinctive repertoire of veils and shadows and hauntings – are eerily magnificent and inimitably his own. No other poet could have conceived the extraordinary opening lines of the ‘Hymn to Intellectual Beauty’: ‘The awful shadow of some unseen Power/Floats though unseen amongst us’. Not even a Power, but the shadow of a Power, so already placed at two removes from anything like concrete presence; and then the oddly effective insistence involved in repeating the word ‘unseen’, as though he were struggling to capture the Power’s sheerly counter-empirical invisibility by doubling up the word.
more here.