Professional practice in clinical and educational contexts frequently operates under a “naive realist” assumption: that professionals and subjects inhabit an identical world, accessible through standardized metrics. This presumes that the professional’s sensory capture constitutes an objective baseline rather than a specific, stabilized interface. We argue that no practitioner—particularly in mental health or education—can legitimately assume that their perceptual field equates to ontological reality. This error drives a systematic structural failure we term epistemic appropriation: the professional’s fundamental inability to conceive that the Other inhabits a legitimately different perceptual reality. Drawing on the Trace & Trajectory Framework (TTF) and Interface Theory of Perception, we provide formal tools to map what critical literature terms “minoritization” and “epistemic injustice.” Epistemic appropriation operates through three complementary manifestations: flattening (the dominant agent’s geometric collapse of the Other’s autonomous identity space into a marginal subset of their own navigational terrain); internalization (the subalternized agent’s coerced construction of self-access routes through dominant-compatible positions); and trajectorial refraction (resistance operations that disrupt the appropriation cycle—counter-exonymy and autonymy exemplify this mechanism). We model this asymmetry endogenously through an Asymmetry Function (gasym) that specifies how differential stabilization dynamics produce navigational inequality: massive institutional recurrence generates configurations whose elevated maintenance costs are collectively distributed and rendered phenomenologically invisible through mimetic naturalization, thermodynamically overwriting fragile autonomous trajectories that bear their full maintenance burden without collective support. Critically, intersubjectivity occurs not through shared ontological space but via transductive coupling—systematic correspondence between distinct navigational interfaces, where asymmetry resides not in the coupling mechanism itself but in the differential Transductive Coupling Costs imposed by exchange protocols and historically saturated semiotic patterns. This formalization distinguishes epistemic appropriation from internalized oppression, provides operational indicators for detecting these dynamics in professional practice, and makes implicit ontological erasure analytically tractable.