 Thus it is argued that even if a zombie world is indeed conceivable, it does not follow that there are nonphysical properties in our world. If that is right, physicalists can concede the conceivability of zombies while insisting that the properties we pick out in terms of phenomenal concepts are physical. ‘Given that properties are constituted by the world and not by our concepts’, Brian Loar comments, ‘it is fair of the physicalist to request a justification of the assumption that conceptually distinct concepts must express metaphysically distinct properties’ (Loar 1999, 467; see also his 1997). He also argues that phenomenal concepts are ‘recognitional’, in contrast to physical concepts, which are ‘theoretical’. Phenomenal concepts, Loar says, ‘express the very properties they pick out, as Kripke observed in the case of ‘pain’’ (1999, 468). He thinks these points explain the conceivability of a zombie world, while maintaining that there is no possible world in which the relevant physical properties are distinct from consciousness. Chalmers objects that Loar’s account does not justify the view that physical concepts refer to phenomenal properties (1999, 488). He argues further (2007) that exponents of this approach face a dilemma. Let C be whichever psychological ‘key features’ we have but zombies lack. Then if it is conceivable that the purely physical facts about us should have held without C, then C is not physicalistically explicable. On the other hand, if that is not conceivable, then in his view C cannot explain our epistemic situation as contrasted with that of zombies. So either C is not physicalistically explicable, or it cannot explain our epistemic situation. (For discussions see Ball 2009; Balog 2012; Carruthers 2005; Chalmers 1999; 2007; 2010; Crane 2005; Loar 1990/97; Papineau 2002; Pereboom 2011; Stoljar 2000; Tye 2008.) 