The rules of treaty interpretation are ordinarily met with scepticism not only by critically-minded international law theorists, but also by mainstream international legal scholars who otherwise believe in international law's normative power. The objective of this article is to inquire whether, despite their much-discussed shortcomings, the rules of treaty interpretation have any 'cash value' in the sense given to this expression by one of the founding fathers of the philosophy of pragmatism William James, in other words, whether they make any practical difference. To do so, this article revisits the traditional understanding of the rules of treaty interpretation and argues that they cannot directly bridge the gap between the signifier and signified, but rather are designed to impose a 'common discipline' with respect to the admissible means that can be used in treaty interpretation.