In the excavated texts of Mawangdui and Guodan, the characters 陰 yin1 and 陽 yang2 were not found, and in the commonly circulated versions, Yin and Yang were found only in chapter 42, entitled the “Transformation of Dao” (道 dao4 化 hua1) by 河 he2 上 shang4 公 gong1.
I think he inferred Yin Yang with his various examples.