But this case is quite different from the first because quantum physics replaced Newtonian physics, much as the theory of heat replaced that of caloric. Again, these questions cannot be pursued here but they serve to indicate the way in which the specific problems raised in the following papers bear on the most central debates in cognitive science. The same anxiety about the status of theoretical models can be seen in Latimer's response to his students' question about the significance of the units in a connectionist system. It is perhaps worth signalling in advance that Latimer's discussion appears to collapse two issues which ought to be kept distinct - namely, the question of the precise theoretical import of certain postulates and the question of the status of postulates per se in science. Thus, Latimer raises the general instrumentalist - realist debate in the philosophy of science here, whereas the puzzle over the precise meaning of the nodes in a connectionist model is a detailed theoretical question specific to this domain.
Instrumentalism is the view that our theoretical entities are merely useful calculating devices.
This is, once again, the idea that our models are not to be taken literally but only as 'convenient fictions' or metaphors. However, neither instrumentalism nor realism can answer the students' question concerning the best way to interpret the units in a neural net. Some admitted, only half in jest, to not knowing what a rule is - despite working with them and postulating them in the course of actual theorising. I hasten to add that this is not a criticism of practitioners, since efficiency in any domain of expertise often requires precisely such inarticulate unreflective behavior - at least until the smooth performance is interrupted by a problem. Then, in the practice of science, just as in the control of action, the emergence of 'anomaly' is just when a self-conscious attention to fundamental principles is called for.