Rule-like behaviour is found throughout human language, provoking a number of apparently conflicting explanations. This paper frames the topic in terms of Tinbergen’s four questions and works within the context of rule-like behaviour seen both in nature and the non-linguistic domain in humans. I argue for a minimal account of linguistic rules which relies on powerful domain-general cognition, has a communicative function allowing for multiple engineering solutions, and evolves mainly culturally, while leaving the door open for some genetic adaptation in (...) the form of learning biases. (shrink)