 Newell and Simon’s idea that programs are theories has been shared by the cognitive scientists Pylyshyn (1984) and Johnson-Laird (1988). Both agree that programs, in contrast to typical theories, are better at facing the complexity of the simulative process to be modelled, forcing one to fill-in all the details that are necessary for the program to be executed. Whereas incomplete or incoherent theories may be advanced at some stage of scientific inquiry, this is not the case for programs.