The introduction provides the definitions and the historical backgrounds of the words śūnyatā, kenosis, and fanā’. It examines the “emptiness-fullness” scheme that is present in many religious traditions. Christian theology operates with kenoma and pleroma, whereas the Sufi tradition operates with fanā’ and baqā’. The Hindu pūrnata, though meaning fullness and perfection in Hindi, is not the contrary of śūnyatā and therefore not comparable with pleroma and baqā’. The unity brought about by fanā’ can be called tawhīd, which signifies the indivisible oneness of God that is the basis of monotheism. Since fanā’ breaks down the individual ego, it leads to an awareness of unity between God and the world. Fanā’ and tawhīd also concern the perception of reality. We see a clear parallel with Buddhist, especially Zen Buddhist, elaborations. Enlightenment, satori, is basically a vision of Oneness that is perceived because rationalizations of reality are overcome. Haqīqa implies that God is the only source of reality. However, for this to happen, God must be One: only a unified God can create a harmonious and coherent reality. Though the kind of emptiness that the three religions address is predominantly spiritual, philosophical emptiness also has “mundane” functions. In current language, emptiness is a predominantly negative term. Instead, the philosophies that the present study discusses suggest that a further emptying provides a better answer.