Human languages are inextricably a part of our mind/brain. No other animal has a comparable ability with the same complexity and richness that humans do. An important research goal is to better understand this ability for language: What is it that enables human to acquire and use language the way we do? One way of answering this is to argue that there are aspects of our biology that enable us to acquire and use language. This has been the answer that in modern times has been advocated by generative grammar, in particular in approaches developed based on work by Noam Chomsky (1965, 1986, 2009), although its origins are much older. This approach holds that there are universal aspects of language that all humans share. However, it is at the same time evident that languages also differ: A child growing up in Japan will acquire Japanese whereas a child growing up in Norway will acquire Norwegian. An adequate theory of human language needs to be able to account for both possibly universals and language variation. However, a core question is what such an adequate theory may look like
