This paper introduces the MARR Equation™, a conceptual framework for evaluating the viability of recognizable, persistent complexity—what we commonly call “life”—across different spatial and temporal contexts. Originally formulated in 1992 and formalized in 2025, the model integrates four normalized variables: Space Support (S), Time Stability (T), Dimensional Cost (D), and Matter–Energy Availability (M). The central insight of the framework is that higher-dimensional spaces do not provide “more room” for life to emerge; rather, they impose an increasing energetic and organizational penalty that destabilizes atoms, chemistry, information processing, and evolutionary continuity. While exotic forms of organization may exist in high-D or rapidly unstable physical regimes, they would likely be unrecognizable to 3+1-dimensional observers. The MARR Equation therefore serves as a heuristic for understanding why life-as-we-know-it appears confined to a narrow dimensional and energetic window within the broader landscape of possible physics.