 An early version of this argument is from Nick Zangwill (1992), who concludes that multiple realizability across biological species has “never been proven”. The multiple realizability contention assumes a type-identity of mental kinds across species. According to Zangwill this assumption is problematic, given that the obvious sensory and motor differences across species by themselves yield different cause-and-effect patterns at all but the grossest level of description. If successful, Zangwill’s challenge undercuts the multiple realizability argument by denying that the same mental kinds obtain across species, to be realized by different physical mechanisms.