||Zombies are introduced under that name by Kirk 1974 (Campbell 1970 discusses them under the name "imitation man"). Versions of the conceivability argument are mounted by these authors and developed further using two-dimensional semantics by Chalmers 1996. Critics who respond by saying that zombies are not conceivable include Dennett 1995, Thomas 1998, Braddon-Mitchell 2003, and Kirk 2005. Critics who respond by saying that conceivability does not entail possibility include Balog 1999, Frankish 2007, Hill 1997, and Yablo 1999. Chalmers 2009 responds.