This paper presents the Proximal Chemical Mandate Principle, a theoretical framework proposing that behavior in organisms with neurochemical systems is governed by two invariant mandates: reward signal maximization (R↑) and stress signal minimization (S↓). We develop a three-tiered hierarchy where proximal chemical drivers (Px) implement evolved functional objectives (Xm) through object selection criteria (OsC) detected by identifier sensors (I-s), producing ultimate outcomes (Uo) that are environmentally contingent. The framework identifies three environmental domains—Natural Selection Field, Natural Epistemophilia Field, and Natural Counterproductive Field—where identical neurochemical optimization processes yield adaptive, mixed, or maladaptive outcomes respectively. We integrate evidence from neuroscience and propose conceptual thought experiments to test necessary and sufficient conditions of the mandates. The model suggests consciousness functions as a state reflection of ongoing neurochemical computations rather than as a causal agent, with philosophical implications for understanding agency and decision-making. The framework provides a unified account of behaviors ranging from basic survival to complex cognitive processes through deterministic neurochemical optimization principles.