Modern physics treats the laws of nature as meta-descriptions written ``outside'' the universe. If the universe is complete and self-contained, its governing principles must arise from within: the laws, the state, and the act of evolution are three aspects of a single reflexive process. This paper formalises the concept of reflexive reality, classifies known physical theories by their degree of reflexivity, and illustrates with concrete examples how self-defining dynamics manifest. The central philosophical argument is that a finite, knowable, self-contained universe must obey reflexive laws (conjectural, see taxonomy below). This argument has been formalised and machine-checked in the companion NEMS programme: the Theorem of Foundational Finality~ and the Reflexive Closure Theorem~ provide machine-checked backing (both proved in Lean~4, zero sorry). This paper presents the physical intuition and conceptual framework; readers seeking formal proofs are directed to the NEMS companion papers~.