Inspired by the work of Wilfrid Sellars, Michael Williams launches an all-out attack on what he calls "phenomenalism," the idea that our knowledge of the world rests on a perceptual or experiential foundation. The point of this wider-than-normal usage of the term "phenomenalism," according to which even some forms of direct realism deserve to be called phenomenalistic, is to reveal important continuities of thought between theories often believed to be competitors.