What is progress, and true sustainability? Can the rational be separated from the spiritual? What can we learn from indigenous knowledge? Paul Barclay speaks to Tyson Yunkaporta, author of "Sand Talk", which provides an entree into indigenous thinking, and an insight into how this knowledge is formed and passed on. "Yarning", according to Tyson, is central. Ghosts, too, loom large in Tyson’s world. He describe how he was once attacked by a ghost as writer’s retreat.