Rule of law is a concept that is regularly debated by legal philosophers, often in connection to discussion of the concept of law. In this article, the focus is not on the substance of the conceptual claims, but on the methodologies employed by legal philosophers, investigating seminal articles on the rule of law by Joseph Raz and Jeremy Waldron. I argue that their philosophical argumentations often crucially depend on empirical or legal doctrinal arguments. However, these arguments remain underdeveloped. I explore (...) how these arguments could be linked to approaches related to rule of law in different fields of legal scholarship and investigate how the methodologies of these fields may complement each other. Thus, the article aims to provide an argument for a specific form of triangulation of three kinds of approaches to the rule of law: philosophical, social-scientific and legal doctrinal. This method of triangulation is illustrated by a discussion of the World Justice Project’s Rule of Law Index. (shrink)