The theory of Gradation is one of the few problems that has attracted the attention of all philosophical schools (Peripatetic School, Illuminationist School and the Transcendent Philosophy) and Muslim logicians, mutakallimun, and gnostics. It is indeed because of this careful attention of Muslim thinkers that this theory has gradually flourished and attained relative and acceptable perfection in its process of development. This theory has greatly influenced logical and philosophical semantics, as well as the epistemology and cosmology of Muslim philosophers and gnostics. The theory of Gradation has been propounded in response to the following question: Is the reality of being one or many? The answer to this question, in a way, reveals one's philosophical and cosmological propensity. Generally speaking, there are three main responses to this question:1. The reality of being is "one", and there is Unity in the world (gnostics' view)2. The reality of being is "multiple", therefore, there is multiplicity in the world (this view is attributed to the Peripatetics).3. The reality of being is both one and many (Sadrian philosophers' view).The most important debate and its outcome in this regard have emerged in the cosmology of Sadrian gnostics and philosophers. Here, gnostics believe in the theory of "Gradation in the loci of the manifestations of being". However, Sadrian philosophers advocate the theory of "Gradation in the levels of being". In this paper, while explaining the historical development of the problem of Gradation, the writer has discussed the views of Muslim gnostics, mutakallimun, philosophers, and logicians in this regard.