"While there has been a lot of research on asymmetry and antisymmetry in syntax, symmetry has been mostly ignored or claimed to be outright impossible (Kayne 1994, Di Sciullo 2002, 2005). This is somewhat surprising from a biolinguistic perspective, which seeks to integrate linguistics with the natural sciences, where symmetry is the normal state of affairs and asymmetry requires an explanation (as pointed out by Boeckx and Piattelli-Palmarini 2005, Brody 2006, Chomsky 2005, Jenkins 2000, among others). My main goal in this book is to remedy this gap by examining symmetric aspects of three fundamental syntactic mechanisms: the mechanism responsible for recursion, the mechanism responsible for displacement, and the mechanism responsible for determining the categories of syntactic objects. I look at these three mechanisms through the lens of Chomsky's minimalist program, which takes the mechanism responsible for recursion to be External Merge (often referred to simply as Merge), the mechanism responsible for displacement to be Internal Merge (often referred to simply as Move) and the mechanism responsible for determining categories of both Merge and Move structures to be Labeling"--