We rebut the objections to the Copenhagen interpretation of quantum mechanics presented by Park [9,10], Margenau [10], and Popper [11]. It seems to us that these authors, having adopted different interpretations of quantum mechanics, have been unable to grasp the perspective of the Copenhagenist. They therefore miss the points which the Copenhagenist is making when he: accords a special status to observations in quantum theory; attributes a state vector to an individual system; places restrictions on the simultaneous measurability of non-commuting (...) observables; hesitates to use his measurements for retrodictions. In our opinion, the arguments of the above authors reflect their incomprehension of Copenhagenism. Elsewhere [5,6] we have discussed two alternative interpretations of quantum mechanics which we have called Copenhagenism and Popperism. We have there shown how the dispute between the schools stems from disparate uses of the word ‘state’. We continue the discussion here within the context of the above points and show how these disparate notions of state are related to diverse notions of ‘behaviour’. (shrink)