Case optionality by movement: Rethinking the Tibetan ergative

In the grammatical tradition of Tibetan, the ergative case (བྱེད་སྒྲ་, byed sgra) has been described as obligatorily present only when the subject receives pragmatic emphasis and optional in discourse-neutral contexts (McGregor 2010; DeLancey 1984, 2011, among others). This presents a challenge to theories of ergative case assignment, which view the ERG case as either inherent to its 𝜃-role (Legate 2006, 2008) or dependent on the configurational relationship between two nominals (Marantz 1991; Baker 2014). In this talk, I present novel fieldwork data on adverb ordering, nominalization, and prosody, which support a movement-based analysis of case optionality. Specifically, I adopt an AGREE-based dependent case framework in the style of Poole (2024) that allows ERG and ABS to be assigned non-simultaneously in a clause bifurcated into two assigning domains. With the Voice head mediating dependent ERG, this analysis also predicts case alternations in raising-to-ergative constructions and non-canonical word orders.