"Warum Flexionsklassen?" lautet ein synchron ausgerichteter Aufsatz von BERND WIESE (2000), an den dieser Beitrag aus diachroner und dialektaler Perspektive anschließt. Das hier zur Diskussion stehende Phänomen, nämlich die notorische Persistenz von Flexionsklasse (im Folgenden "FK") über Jahrhunderte, ja sogar Jahrtausende hinweg, dürfte noch eines der größten linguistischen Rätsel darstellen, die ihrer Lösung harren. HASPELMATH (2002, 115) eröffnet in seinem Band "Understanding Morphology" das Kapitel über "Inflectional paradigms" mit folgenden Worten: "Perhaps the most important challenge for an insightful description of inflection is the widespread existence of allomorphy in many languages."
Ta date, the existence and persistence of inflectional classes remains largely unexplained - inflectional classes appear to only produce allomorphs, with no informationaI gain. There is hence no shortage of approaches postulating the decline of inflectional classes, or at least that they are conditioned, i.e. motivated, by external (non-inflectional) characteristics like semantics, phonology or prosody. Such approaches "motivate" weak masculine nominal forms for animate objects or preterite-present forms for modal verbs. From a linguistic historical perspective, however, these are exceptional cases. Inflectional classes are all too seldom considered in their diachronic and dialectal context, something this article, while concentrating on noun class in German and its dialects, tries to do. It emerges that inflectional classes are definitely not in universal decline (indeed, they are often expanding); rather, the tendency is toward consolidation with the pronounced word and toward interlinking with other category markers (here, case and especially number). It is precisely here that a possible use for inflectional classes can be posited: they enable allomorphic variation, i.e., the creation of a pool of inflections from which, using functional criteria of the so-called "host category" (Wirtskategorie, in this case the plural). The investigation of five dialects further reveals that inflectional classes are also maintained in varieties with no written or normative controls, as long as distinctions of gender - that second. largely arbitrary classification system - are not reduced. The article also focuses on the ambivalent and diachronically variable relation between gender and inflectional class. The theory is advanced that the two classifications complement one another and thus reinforce the category of number, to which they are both linked (gender bolstering the singular, and inflectional class the plural) - over time, gender has retreated from the plural and inflectional class from the singular.