Suppletion, natural morphology, and diagrammaticity

This paper challenges the widespread view of suppletion as nothing but morphologically nonfunctional diachronic residue. Within natural morphology, suppletion has generally been treated as an "unnatural" phenomenon that must be accounted for in extragrammatical terms. A richer notion of diagrammatic iconicity, however, inspired largely by Bybee's work, leads to an analysis in which suppletion in semantically generic, grammaticalized or grammaticalizing items fits quite well into the overall diagrammatic structure of inflecting languages in a way that is consistent with the main principles of natural morphology. I consider Bybee's view that all iconicity/structure should be regarded primarily as an epiphenomenal artifact of use and change but argue that some aspects of morphological change can most easily be understood if we grant some degree of psychological reality to diagrammaticity.