How does human language arise in the mind? To what extent is it innate, or something that is learned? How do these factors interact? The questions surrounding how we acquire language are some of the most fundamental about what it means to be human and have long been at the heart of linguistic theory. This book provides a comprehensive introduction to this fascinating debate, unravelling the arguments for the roles of nature and nurture in the knowledge that allows humans to learn and use language. An interdisciplinary approach is used throughout, allowing the debate to be examined from philosophical and cognitive perspectives. It is illustrated with real-life examples and the theory is explained in a clear, easy-to-read way, making it accessible for students without a background in linguistics. An accompanying website contains a glossary, questions for reflection, discussion themes and project suggestions, to further deepen students understanding of the material.