Before starting the comparative discussion of philosophical and theological terms, in Chap. 1 , I set the ground, present the main themes, and check the vocabulary that is going to be used. The chapter clarifies problematic definitions of, for example, the distinction between emptiness and nothingness, Since the introduction of the Mahāyāna śūnyatā into China, the term underwent Daoist transformations, and in Buddhist philosophy, emptiness and nothingness are often treated as synonyms. Fanā’ is submitted to similar ambiguities. Fanā’ is often translated as annihilation, and one often speaks of the obliteration of the self. However, ‘emptiness’ or ‘emptying’ remain strongly related meanings. Baqā’, which is designated as the opposite of fanā’, literally means “continuance” or “survival,” and is thus the opposite of death, and baqā’ is also presented as “fullness” (with God). Further, the chapter considers the meaning of God in various religions as well as the problem of unity and multiplicity. It also evaluates the temptation of a “perennial philosophy” of emptiness, which will eventually be rejected.