The goal of this contribution to the Elements series is to closely examine Merge, its form, its function, and its central role in current linguistic theory. It explores what it does (and does not do), why it has the form it has, and its development over time. The basic idea behind Merge is quite simple. However, Merge interacts, in intricate ways, with other components including the language's interfaces, laws of nature, and certain language-specific conditions. Because of this, and because of its fundamental place in the human faculty of language, this Element's focus on Merge provides insights into the goals and development of generative grammar more generally, and its prospects for the future.

In this pioneering study, a world-renowned generative syntactician explores the impact of phenomena known as 'third factors' on syntactic change. Generative syntax has in recent times incorporated third factors – factors not specific to the language faculty – into its framework, including minimal search, labelling, determinacy and economy. Van Gelderen's study applies these principles to language change, arguing that change is a cyclical process, and that third factor principles must combine with linguistic information to fully account for the cyclical development of 'optimal' language structures. Third Factor Principles also account for language variation around that-trace phenomena, CP-deletion, and the presence of expletives and Verb-second. By linking insights from recent theoretical advances in generative syntax to phenomena from language variation and change, this book provides a unique perspective, making it essential reading for academic researchers and students in syntactic theory and historical linguistics.