 Late in life, in his final memorial to the throne, Xi Zuochi laid bare his rationale and method behind delegitimating Wei while conducting the balancing act of considering the Jin dynasty still legitimate.Xi Zuochi's heterodox theory met with little acceptance during his lifetime or in the centuries immediately following his death.It was not until the Song dynasty when Ouyang Xiu and Sima Guang echoed his criteria for dynastic legitimacy that mainstream historiography embraced Xi Zuochi's thought.