David Chalmers has defended an account of what it is for a physical system to implement a computation. The account appeals to the idea of a “combinatorial-state automaton” or CSA. It is unclear whether Chalmers intends the CSA to be a computational model in the usual sense, or merely a convenient formalism into which instances of other models can be translated. I argue that the CSA is not a computational model in the usual sense because CSAs do not perspicuously represent algorithms, are too powerful both in that they can perform any computation in a single step and in that without so far unspecified restrictions they can “compute” the uncomputable, and are too loosely related to physical implementations.
Curtis Brown, “Implementation and Indeterminacy,” in J. Weckert and Y. Al-Saggaf, eds., Conferences in Research and Practice in Information Technology 37 (2004): 27-31.
Conferences in Research and Practice in Information Technology