Three centuries after Dryden wrote this passage, the work he refers to is still ‘wanted’ and the chief obstacle which confronts the student of any of the ‘kinds’ of literary dialogue remains the lack of any substantial and coherent theoretical discussion of the genre. As Dryden notes, the Ancients – and most significantly Aristotle – gave little indication of what form such a theory might take, and subsequent critics have found themselves rather in the position of Northrop Frye's Renaissance doctors, who refused to take syphilis seriously because Galen had made no mention of it. For a brief period in the sixteenth century in Italy, when the vogue for the literary dialogue was at its height, there was a sustained attempt to bring the dialogue into the fold of Aristotelian genre criticism. But this initiative waned with the subsequent decline in the popular fortunes of the genre, and its provisional conclusion – that the dialogue was, in Tasso's formula, a fusion of dialectic and poetry – did not stand the dialogue in good stead in eras when poetry and non-poetry were ever more rigorously distinguished.