Robert Levine's research and publications focus on applications of category logics to a range of empirical phenomena, including filler/gap dependencies, noncanonical coordinations and their interaction with syntactic and semantic properties of scopal phenomena, and the treatment of ellipsis in natural deduction formulations of type-logical categorial grammar. Most of his current research is devoted to exploring the properties of hybrid proof theories for category logic that include both directional (Lambek calculus) and nondirectional (lambda-calculus) modes of implicational inference.