Type frequency is not the only factor that determines productivity, so the Tolerance Principle is not enough

Abstract Inflection classes that have many members often gain members from classes that have fewer. While this tendency is often pointed out in diachronic linguistics, the American psycholinguist Charles Yang (2016) goes further. He claims this to be always the case, so that minority classes cannot be productive at the expense of majority classes, and that productivity actually can be predicted. By this view, productivity is a direct function of type frequency; there are no other factors determining whether a pattern is productive. The claim of this paper is that type frequency is not the only factor determining productivity, and that while Yang’s approach, the ›Tolerance Principle‹, is interesting, it cannot be upheld in its present form. The paper presents an example of suppletion spreading in Germanic, and it presents examples of minority patterns spreading in North Germanic. Parallels outside of Germanic are pointed out. Also, it is argued that Yang’s (2016) analysis of English verb inflection and German noun inflection is insufficient, so these important case-studies, presented in favour of the Tolerance Principle, do not support it. In general, the paper emphasises the importance of ›local generalisations‹ and of seeing language as a ›system‹ of low-level regularities, not all-encompassing rules. While type frequency certainly seems important for productivity, inflectional morphology is a complex matter; productivity is also influenced by various factors of a more structural nature.