This document defines the governing doctrine of SAFE-Matter™, establishing a deterministic framework for admissibility, authority, and enforcement in life-critical systems. Current safety models rely on historical validation, periodic inspection, and inferred system continuity. These approaches do not establish the condition that matters most: whether a system is safe to rely upon at the exact moment it is required. This structural gap is defined as the Unknown Present. SAFE-Matter introduces a governing condition in which no system state is permitted to act without admissible proof at the point of execution. Proof is defined as verifiable, attributable, and current evidence sufficient to justify action. Where proof cannot be established, execution is not permitted. The doctrine defines equilibrium as a system state in which only provable conditions persist as actionable reality. Unproven states are excluded from execution and cannot produce consequence. Authority is therefore relocated from historical validation to the moment of reliance. SAFE-Matter does not enhance existing safety frameworks. It redefines the condition under which they are permitted to operate, replacing assumption with proof, tolerance with exclusion, and observation with enforcement. This doctrine forms part of a broader body of published work examining the structural limitations of safety governance and the evidentiary gap at the moment of reliance.