The Dictionary of the Complete Vocabulary used by Friedrich Schiller, which is currently being compiled in Jena, displays morphological variants for numerous entries. The declension of foreign expressions in particular exhibit variation and thereby a kind of implicit uncertainty concerning which regularities apply. For instance, three different plural forms of the substantive Zar occur almost next to one another: Czaren, Czars und Czare. Today the speaker would decide on at least one of the variants, but Schiller's fluctuating use of language occurs within the bounds of a single speaker's grammatical competence. It is demonstrated how the influence of dialects, foreign pronounciation and the intended integration of these forms in the High German declension paradigm interact. It becomes obvious that Schiller was "experimenting” with the inflection of foreign terms. The conceptual basis of Optimality Theory makes it especially suitable for the explanation of such idiolect variance. It has the advantage over other theories that a number of competing grammatical systems need not be postulated.