The tension between belief and fact arises from the nature of espionage, which relies on the art of deceit—The Spy Who Came in from the Cold is the first of many novels in which John le Carré explores the idea of deception and its complex relationship to the truth. Someone’s beliefs point to a truth about their own character, even if specific facts fail to bear out those beliefs in key instances, or they have been brought to a broadly correct conclusion through false or incomplete facts. Leamas’s mission requires him to establish that Mundt is a double agent for the British without knowing that Mundt really is a double agent. For all of Leamas’s cynicism, he does not believe that the Circus would sacrifice so many lives to protect an asset. Aside from moral considerations, Leamas is a proud man, and he is confident that, as station head, he would have been told if Mundt was working for the British.

Furthermore, there is a strong hint of truth to Leamas’s decline even though it is part of his operational cover. He was already a gruff man, prone to heavy drinking, and extremely resistant to emotional intimacy. Even if punching the grocer is part of the act, it cuts him off from the Circus and leaves him with meager employment opportunities after he is released from prison.