The papers by Ronald de Sousa and Steve Davis raise very interesting issues. I think that they have the issue almost right between us, but I want to make some small amendments, which will make a big difference.
First, de Sousa: with all the talk about the ‘significance feature,’ I’m not trying to make an in principle argument against the reduction of purpose/action to physical movement/change. Perhaps such an argument is possible, perhaps not. For the moment, all we have is the a posteriori. But that involves our making the most dear-headed possible judgments about our actual intellectual predicament, using this term as a shorthand for a whole set of issues to do with the nature of the phenomena we face, and how they relate or don't relate to the theories on offer. Philosophy can help in this, not because philosophers wheel in bright, shiny a priori (im)possibility arguments, but rather by clarifying what is at stake, and what is going on.