In this paper, the lexical semantics of the pre-modal verb 得 dé and its development into a modal auxiliary will be discussed. Two different positions are available for the modal dé, the default preverbal position of modal auxiliary verbs and a post-verbal position. The analysis of the event and the argument structure of the lexical verb dé reveals that the different modal uses of dé originate from its functions as an achievement verb. In this regard, dé clearly differs from the other verbs of possibility in Late Archaic Chinese. The particular syntacto-semantic constraints of dé can account for its development into both a modal auxiliary verb, and for the particular functions it develops in the Modern Sinitic languages as a postverbal modal marker.