 The generalized correspondence principle here is seen both as a constraint on the development of new theories and as an account of how successor theories are related to their predecessors. Typically in physics, Post’s notion of ‘degenerating’ is cashed out as the limit of some parameter whereby the equations of a successor theory are recovered as the limit of the equations of predecessor theory. Regarding the specific case of the quantum-classical relation, Post argues that the general correspondence principle fails: