 As Nathan Sivin (1990 and 1995) has argued, Chinese accounts focused on specific sciences, rather than on one unified notion of science. These Chinese sciences were both quantitative and qualitative. Sivin (1982 and 1990) breaks down the quantitative sciences into three disciplines: mathematics (suan 算), mathematical harmonics or acoustics (lü 律 or lü lü 律呂) and mathematical astronomy (li 歷 or li fa 歷法), considered related to harmonics. Sivin describes the qualitative sciences as: astronomy or astrology (tian wen 天文), medicine (yi 醫) and siting (feng shui 風水). Tian wen included the observation of celestial and meteorological events whose proper reading could be used to rectify the political order. Medicine included “Nurturing Life” (yang sheng 養生), a broad category that included a wide range of self-cultivation techniques with important philosophical implications. In later periods, medicine also included materia medica (ben cao 本草) and internal (nei dan 內丹) and external (wai dan 外丹) alchemy.