Chen Shou's treatment of the legitimacy issue was generally accepted through to the Northern Song dynasty. Despite maintaining that none of the three states truly held the Mandate of Heaven since they all failed to unify China, Song historian Sima Guang used Wei's era names and thus affirmed the legitimacy of Wei's succession to Han in his universal history "Zizhi Tongjian". Sima Guang explained that his choice was merely out of convenience, and he was "not honouring one and treating another with contempt, nor making distinction between orthodox and intercalary positions." Nonetheless, the influential Neo-Confucian moralist Zhu Xi criticized Sima Guang's choice, taking the position that Shu Han was the true successor to the Han dynasty since Liu Bei was related to the imperial Liu clan by blood, and thus used Shu's calendar in his rewrite of Sima Guang's work, the "Zizhi Tongjian Gangmu". This position, first argued by Xi Zuochi in the fourth century, found support in Zhu Xi's time since the Song dynasty found itself in a similar situation as Shu Han, as it was forced out of north China by the Jurchens in 1127 and became known as the Southern Song. The revisionist private histories of the time emphasized "humane governence" (仁政) as a mark of legitimate dynastic succession, and saw Liu Bei as an idealized Confucian monarch. The pro-Shu bias then found its way into popular forms of entertainment such as "pinghua" tales and "zaju" performances, and was eventually codified in the 14th century historical novel "Romance of the Three Kingdoms".