 Terms meaning “long life” (shou, changsheng) and “immortality” (busi, etc.) are among the most recurrent ones in Daoist literature. Both have been understood in different ways according to the perspectives of the respective texts and authors. In general, liberation has been represented in Daoism according to two main models: “union with the Dao” (hedao and similar terms) and incorporation into the celestial bureaucracy (not as a deity, but as an officer of that bureaucracy). The highest form of liberation is often described as “ascension to Heaven” (shengtian), attaining “celestial immortality” (tianxian), or in analogous terms, but the general concept of immortality has been construed in many ways.