This work challenges several fundamental assumptions of modern physics, proposing an alternative nature in which proper time, its property, rather than the geometry of spacetime, constitutes the main physical variable. It argues that key concepts traditionally considered fundamental—namely, spatial contraction, the invariance of the speed of light as an absolute natural limit, and the strict separation between the nature of matter and radiation—are interpretative constructs, rather than inevitable consequences of empirical evidence or mathematical formalism.In this framework, relativistic phenomena emerge from variations in the temporal regime of physical systems, determined by their energy conditions, without requiring any physical contraction of space. Proper time is elevated to a defining criterion of materiality: systems that possess internal dynamics exhibit proper time, while its absence defines a distinct physical regime.Rest mass is reinterpreted as a regime-dependent parameter, associated with the existence of proper time, rather than a fundamental attribute of matter. C is reformulated as a limit that separates regimes with and without proper time, rather than a purely kinematic limit. From this perspective, light is described not as an entity distinct from matter, but as an extreme state of matter characterized by zero proper time and zero rest mass, while still maintaining full physical capacity for interaction.In this approach, the need for physical space contraction is eliminated, while remaining compatible with established experimental results. The proposed framework offers a unified and conceptually unified interpretation of matter, energy, and radiation, and opens the possibility of new experimental criteria capable of distinguishing between the geometric and temporal nature of physical reality.