Abstract: This dissertation explores the developmental trajectory of Principle C effects in young children’s interpretations as a means to identify the underlying knowledge driving interpretation in these contexts. While previous research has shown that children show a restriction on interpretation in Principle C contexts as young as 30 months (Lukyanenko, Conroy & Lidz, 2014), the task remains to show that this behavior is attributable to knowledge of Principle C. I discuss a series of alternative mechanisms for interpreting reference relations in Principle C contexts that have been proposed to account for this behavior instead of knowledge of Principle C. I compare children’s interpretations in multiple linguistic contexts, showing that Principle C is the only proposed mechanism which is able to account for all performance. I present a novel analytic approach to identifying the underlying knowledge driving behavior, which utilizes individual differences in deployment mechanisms to predict individual differences in interpretation. The results show that children’s syntactic processing correlates with their interpretation in Principle C contexts, suggesting that the mechanism responsible for interpretation is inherently structure- driven. Finally, I explore the implications of this research in two debates related to identifying the nature of the Principle C constraint: (1) whether Principle C is a component of grammatical knowledge which is learned from the input or innately specified as part of Universal Grammar; and (2) whether Principle C should be considered a primitive of grammar or a set of effects which are derived from pragmatic principles.