This chapter retraces the way in which the Austrian philosopher Sir Karl Popper came to accept a Correspondence Theory of Truth from the work of the Polish logician and mathematician Alfred Tarski. It is argued that Popper's use of Tarski's semantic theory of truth reveals crucial insights into the fundamental characteristics of Popper's social philosophy. Quite deceptively, arguments based upon Tarski's theory of truth appear implicitly throughout the text of The Open Society and Its Enemies (1945). It is then demonstrated how Popper integrated a correspondence theory of truth into a theory of the functions of communicative language that he received from Karl Bühler.