Dr. Michael A. Gilbert is Professor of Philosophy at York University in Toronto, Canada. He is the author of Coalescent Argumentation (1979), as well as two novels and numerous scholarly articles.
Had this as a textbook for an English class this spring, Advanced Composition (last class of my undergrad!). It's pretty theoretical but uses a lot of good examples and deconstructs the process of articulating and perceiving arguments. Does a decent job of encouraging arguers to pay close attention to both points of convergence and divergence in any good argument.