 Schaffner has argued that the structuralist notion of reduction is too weak a notion to be useful, and that (official) Nagelian reduction is a special case of Suppes’ model. That is, whenever there is a Nagel-reduction, then there is a Suppes-reduction. Moreover, according to Schaffner, Suppes’ model covers cases that should not be covered, namely, arbitrary reductions (Schaffner 1967). Similar problems arise for successors of Suppes’ model that try to cash out reduction in terms of an isomorphism or an analogy-relation, which have been developed and refined by Sneed (1971) and Stegmüller (1979). The basic problem of these accounts has been described by Moulines (1984: 55) and a similar idea can be found in Hoering (1984). Moulines puts it as follows: