Skinner rejects models because he thinks the data will explain themselves.
Skinner conflates internal mental theory with any internal theory at all.
Inference about the causal basis of the data. Introspection doesn't get you out of scientific trouble, it gets you into it. But reinforcement doesn't get you out of it either. Only a causal theory of behavioural capacity will. Neural activity is surely the basis of both behavioural capacity and mental states.