The question is then how, under these circumstances, one is to understand, for example, the usual ‘explanation’ of the phenomenological gas equation via the kinetic theory, in particular, the ‘explanation’ of the phenomenological temperature via the average kinetic energy of the molecules. Feyerabend assumes that according to Nagel’s ‘natural’ conception of reduction, none is actually available because the meaning of the word ‘temperature’ is not preserved. By contrast, he makes the claim “such a change to new meanings …is a natural occurrence which is also desirable for methodological reasons” (Feyerabend 1981a, 81). But, in defense of Nagel, it must be said that this is made clear enough, despite some already mentioned uncertainty in the matter, when he expressly requires as part of heterogeneous reduction not the above quoted passage invoked by Feyerabend, but rather his ‘conditions of connectability’. And Nagel (1961, 357) has not overlooked the fact that heterogeneous reduction should provide a change of meaning.

The Reduction of Physical Theories by Erhard Scheibe