It's generally believed that cognition is a distributed process as in Brooks' Subsumption Architecture or Dennett's Multiple Drafts theory, as well as in other theories of consciousness and cognition. If this is the case, how did we evolve what appears to be the centralized control and descision system known as volition? Is our volition just an illusion? Wayne Christensen argues that it is not an illusion in a newly released paper (PDF format) that will be a chapter in a forthcoming MIT book. He proposes selective pressures operating in evolution, favoring distributed systems with an executive control system that achieves coherent focus and resolves conflicts among competing subsystems. There are some useful ideas here that apply to mobile robotics and artificial intelligence.