Seamus Perry at the LRB:
Quite a few of Shelley’s contemporaries came to the view that he wasn’t all there – the inhabitants of Marlow, for example, who were treated to the recurrent spectacle of a disgraceful young radical poet returning distractedly to his cottage after long scrambles in the woods. ‘He was the most interesting figure I ever saw,’ a child witness recalled later in life, still much struck. ‘His steps were often hurried, and sometimes he was rather fantastically arrayed … on his head would be a wreath of what in Marlow we call “old man’s beard” and wild flowers intermixed; at these times he seemed quite absorbed, and he dashed along regardless of all he met or passed.’ Not all the neighbours thought so admiringly of him, needless to say; and his poetry too would find detractors as well as admirers, dividing opinion over the next two hundred years with comical extremity. William Hazlitt, although notionally on the same side in the big political questions of the day, was pugnaciously uncharmed by the cast of mind that he discerned in Shelley’s dashing about, and anticipated a whole school of criticism: ‘There is no caput mortuum of worn-out thread-bare experience to serve as a ballast to his mind; it is all volatile intellectual salt of tartar, that refuses to combine its evanescent, inflammable essence with any thing solid or any thing lasting.’ But others found this odd sense of irreality more winning, or at least arresting. Getting to know him for the first time, his future sister-in-law reported delightedly that Shelley behaved ‘just as if he were Adam in Paradise before his fall’, and she was not alone in finding in him an innocence of the world that lay about him.
more here.