In order to understand the human ability for language, we cannot simply focus on the idealized monolingual speaker or signer (Chomsky, 1965). Rather, as much work in second language acquisition has recognized, it is also necessary to study instances where a person masters two or more languages at different levels of proficiency. Today's globalized world with increased migration will further increase the number of multilingual speakers. However, another piece of the puzzle involves understanding the grammatical system of bilingual speakers who use both a sign language and a spoken language, or put differently, bimodal bilingualism. This latter type of bilingualism is clearly yet another possible human I-language (in the sense of Chomsky, 1986), meaning that our theories of the human language faculty also need to accommodate facts from this group of speakers. It is this population that is the focus of the current keynote paper by Lillo-Martin, Müller de Quadros and Chen Pichler (2016, henceforth LMC).Theoretically, there are two main options when faced with a type of speakers that has yet to be adequately described and understood. One can either devise a special theory which only applies to that particular type of speakers, or one can opt for what is typically called a null theory: One theory of the human language faculty irrespective of the number of languages a given individual masters. Occam's Razor clearly suggests a preference for the latter type of theory, presuming that descriptive adequacy can be maintained.In their paper, LMC opt for a null theory. They show how a specific type of theory, namely Distributed Morphology, can be extended to also account for bimodal bilingualism.