Between the rise of fascism and the beginnings of the Cold War, mid-20th century Europe experienced an unprecedented period of ideological rule. Artists and intellectuals were called upon to actively endorse the political ideologies governing their respective regimes, with little room for dissent. In response, many looked back to previous eras in which thinkers were faced with similar pressures. In these reflections, the practice of dissimulation in which believers of one religion or denomination pretended to belong to another took on new relevance. This dissertation traces this upsurge in interest in dissimulation among writers, historians, sociologists and philosophers through the prism of one author – the Polish poet and political exile Czesław Miłosz – and one concept: Ketman. Miłosz popularized this Persian word term, which denotes the duty of believers to conceal their true beliefs when faced with mortal peril, in his 1953 book The Captive Mind. In doing so, he made Ketman a byword for the myriad strategies of concealment and self-effacement used by inhabitants of the Soviet Bloc. This work presents a global history of Ketman, beginning with its articulation by Islamic jurists and its discovery by Western Orientalists, through its re-appropriation by Miłosz and his readers both in Communist Poland, and in the world at large. In sketching the various personal and intellectual influences acting on Miłosz, and the numerous authors he influenced in turn, it makes a case for dissimulation as structuring precedent for thinkers enmeshed in later periods of ideologically- driven authoritarianism.