Within linguistics, the formal and functional approaches each offer insight into what language might be and how it operates, but so far, there have been hardly any systematic attempts to integrate them into a single theory. This book explores the relationship between universal grammar - the theory that we have an innate mechanism for generating sentences - and iconicity - the resemblance between form and meaning in language. It offers a new theory of their interactions, 'UG-iconicity interface' (UG-I), which shows that not only do universal grammar and iconicity coexist, but in fact collaborate in intricate and predictable ways. The theory explains various recalcitrant cross-linguistic facts surrounding the serial verb constructions, coordination, semantically and categorically obscure 'linkers', the multiple grammatical aspects of the external argument, and non-canonical arguments. This groundbreaking work is essential reading for researchers and postgraduate students in linguistics, as well as scholars in psychology and cognitive science.