Liangtongshu 兩同書 "The two identities" is a philosophical treatise written during the late Tang period 唐 (618-907) by Luo Yin 羅隱 (833-909), original name Luo Heng 羅橫, courtesy name Zhaojian 昭諫, style Master Jiangdong 江東生.
Luo hailed from Yuhang 余杭 (today in Zhejiang) or Xindeng 新登 (modern Fuyang 江富, Zhejiang) and was a retainer of the local military commissioner (jiedushi 節度使) Qian Liu 錢鏐 (852-931, i.e. King Suwu 武肅王, r. 907-931), who made him magistrate (ling 令) of Qiantang 錢塘. In 903, Luo was appointed administrative assistant (panguan 判官) and in 908, when the Wu-Yue empire 吳越 (907-978) was founded by Qian Liu, palace steward (jishizhong 給事中). He died shortly after. In his private life, Luo Yin compiled many books. Apart from the 2-juan-long Liangtongshu, he wrote the books Jiayiji 甲乙集 and Chanshu 讒書, and 12 juan of poems. His collected prose writings (Wenji 文集) have a length of 5 juan.
The Liangtongshu includes ten chapters, the first five of which include thoughts on the Daoist philosopher Laozi, the other five deliberations about Confucius. The first part is seen as a kind of inner contemplation, while the part on Confucius deals with social and political matters. The title is an imitation of Wu Jun's 吳筠 Liangtongshu from the Jin period 晉 (265-420) that is today lost. The Liangtongshu is a text of a valuable literary quality and provides an interesting insight into Daoist and Confucian thought during the Tang period.
It is included in the series Guang miji congkan 廣秘笈叢刊, Ershierzi 二十二子, Tianyige congshu 天一閣叢書, Shuofu 說郛 and Siku quanshu 四庫全書, as well as in the collection Luo Zhaojian ji 羅昭諫集 that was compiled during the Qing period 清 (1644-1911) by Zhang Zan 張瓚.