Establishing an association between unity (of existence) and multiplicity (of essences) is one of the important challenges mystics are faced with. Advocating a sole being while rejecting the existence of others beings makes the impression that in mysticism the external existences are nothing but naught and nil. Regarding the mystic’s established principles in mystical ontology and relying on the genuine mystical sources, one can infer that the aforementioned impression does not conform to the reality. To prove this claim, we consider it necessary to first have a brief survey on the essentialist views of some other schools of thought, and secondly explain the pure being(The Real One, Haqq) according to the mystically ontological viewpoint. Then, in a lower degree, modes and affairs, that is to say Divine Names, and the mediating link among mere existence, inner-realities and essences are introduced. And finally, the link and relationship between inner-realities and essences (eternal entities) with the absolute being are detailed. It is at last concluded that Muslim mystics, with their own special principles, approve of essentialism in a unique interpretation; so that, this essentialism is both in accordance with the Divinity’s being the pure one (personal unity of existence), and in line with the requirements of mystical viewpoints. Through a meticulous explanation of the Being, mystics believe that inner-realities have actuality and are not considered naught and nil.