In this talk, we present a little-discussed puzzle from Clitic Doubling
(CD) in Greek: CD of plural indirect objects is ungrammatical. We argue
that this ungrammaticality is due to a morphological mismatch between the
form of the clitic, which is syncretic for accusative and genitive, and the
form of the determiner, which is not syncretic. We argue that the data
provide support for movement-based theories of CD, and provide a new
diagnostic for distinguishing between CD and object agreement: if
morphological mismatches of the Greek type lead to ungrammaticality, the
relevant phenomenon must be an instance of CD.