Since ancient time our perception of the ultimate external reality evolves as our investigation produces more knowledge by expanding the related disciplines. This phenomenon is illustrated by our vision of space and time, while they were treated separately in antiquity and subsequent ages, they are unified into a continuum in modern time. Furthermore, the theoretical possibility of parallel universes with more than one time dimension are considered in the present age. In this paper, a theory is developed to precisely treat reality along with its associated concepts that arise from the modern scientific investigations. This treatment contributes to a quotient set of realities with five equivalence classes and a qualitative measurement of our current ultimate external reality with its possible evolution based on the related scientific theories and their consequences.