Sonnet 3 (From Dante’s Sixth Sonnet) by Robert Duncan   When I was invited to consider the role of the volta in poetry, my mind was immediately and perversely drawn to the work of Robert Duncan, which has preoccupied me incessantly for the past couple of years. I say perversely because of all the major American poets of the postwar period that occur to me—Frank O’Hara, Alice Notley, John Ashbery, to name one trinity—Duncan’s poetics is possibly the least indebted to the qualities that I associate with the turn, at least at first glance. Where a poet like Ashbery astonishes his reader constantly with his wit, practically line by line, Duncan seems to use no wit at all—if by wit we mean that capacity…