Understanding rules is central to understanding law. However, several issues about the concept of rule remain disputed. One of them was at the center of an important debate in 20th century legal philosophy. Are rules mostly about their texts, as HLA Hart thought? Or are the moral goals pursued by a rule built into its very concept – a position taken by Lon Fuller? Despite many decades of sustained debate, both positions still have proponents and opponents. In this dissertation, I argue that this is partly the result of competing appeals to intuition at the heart of each position. Hart and Fuller evoked thought experiments that elicited conflicting intuitions in each of them. The thought that those reactions to each thought experiment are shared by their target audience is implicit in each author’s appeals. In other words, the authors bet that the members of the target audience should have certain beliefs and attitudes. But there is no evidence of whether this is the case. Experimental philosophy provides the tools needed to tackle this lack of evidence. By working out precisely what empirical claims underlie philosophical debate, it is possible to come up with experiments that test the success of those appeals. In this dissertation, I set out to employ those tools to try to break the stalemate between Hart and Fuller over the roles of text and purpose in the concept of rule. After restating the debate as two pairs of conflicting theses that make empirical predictions, I review recent experimental work surveying the intuitions of laypeople and lawyers about rules. These studies involved thousands of participants in several countries and have important implications for the analysis of the concept of rule. They show that text and purpose are prevalent under different circumstances. Moreover, there are important differences between the intuitions of lawyers (who lean textualist) and laypeople (who lean towards purposes). These differences include a cross-cultural divide, with substantial cultural variation among laypeople, but convergence among lawyers. The evidence also suggests entirely new research questions for general jurisprudence about the precise nature of purposes and interpersonal differences in decision-making style. I consider how each of those findings relate to the broader themes dividing Hart and Fuller (such as the debate regarding the connections between law and morality), as well as the limitations of the existing evidence. Finally, I argue that this model of experimental jurisprudence might be fruitfully applied to other longstanding debates in legal philosophy.