This dissertation analyses Investor-State Dispute Settlement as a Complex Adaptive System. The aim of the dissertation is to contribute to an improved understanding of the emergent and self-organising properties of ISDS with a view to improving our ability to (re)form the system. This MPT consists of Ch2 of the dissertation. This chapter is an introduction to complexity theory, as well as a consequent analysis of the use of complexity theory in law by scholars and practitioners.