Karlgren attempted to unearth Chinese history itself from its linguistic development and diffusion. As he writes in his English adaptation "Sound and Symbol in Chinese" (1923), Chapter I: "Thus, though Chinese traditions give no hint whatever of an immigration from any foreign country, and though there consequently is no external chronological "point d'appui", we are nonetheless able to state, from internal evidence, that the Chinese tradition which places the reign of the emperor Yao in the twenty-fourth century B.C. is correct; that the Chinese even in those remote times were skilled astronomers; that they put down in writing in the Chinese language records of memorable events, and in all probability wrote their accounts soon after the events; in short, that a well-developed Chinese civilization—resting undoubtedly on foundations many centuries old—together with the Chinese language, existed on Chinese soil two thousand years before Christ."