Computationalism’s Weak Spot

Introduction Computationalism, the claim widely held among cognitive scientists that mental states are computational states, has recently come under heavy attack from various directions. Some (especially adherents of connectionism and dynamic systems people”) hold that mind cannot be explained in terms of computation. Others believe that crucial aspects of the intuitive notion of computation are still not well understood and, hence, not reflected in formal definitions of computation. Even the acceptance of standard notions of computation (such as “Turingcomputability”), however, leaves one with an explanatory gap: how are abstract “computations” linked to concrete physical systems? It has been pointed out that a reasonable theory of implementation, which specifies the link between computations and “computers”, is still missing— hence, “walls implement the Wordstar program” and every ordinary open system implements every finite state machine, at least so it is claimed (by Searle 1992 and Putnam 1988, respectively). My goal in this paper is to show that Searle and Putnam’s arguments are based on the same criticism: as long as physical states (of a given physical system) can be chosen freely, one can always relate these physical states to computational states (of an arbitrary computation) in such a way that the physical system can be viewed as implementing that computation. From this I will conclude that unless a better notion of implementation is provided that avoids state-to-state correspondences between physical systems and abstract objects (be they computations or certain kinds of formal theories) computationalism will remain in bad shape.