Across the depth-psychology corpus, ‘Fidelity’ operates on at least three distinct planes that rarely cohere into a single doctrine. In the Taoist I Ching tradition rendered by Liu I-ming and Thomas Cleary, fidelity (hexagram 25, *Wu Wang*) designates an interior state of wholehearted sincerity without duplicity — a cosmological alignment between human will and the spontaneous movement of the Tao, where error arises precisely when the human mind overrides celestial orientation. This metaphysical reading stands in sharp contrast to Esther Perel’s sociological archaeology, which traces fidelity’s historical mutation from a patriarchal instrument of lineage-control to a modern idiom of romantic self-disclosure — a transformation that, paradoxically, renders infidelity psychologically productive as a shadow presence within long-term eros. A third, clinical register governs the treatment-research literature (Miller on MI, Shapiro on EMDR, Avery on therapeutic communities), where fidelity names the measurable adherence of a practitioner to a manualized protocol — a quantifiable property entirely divorced from the interior sincerity the Taoist tradition prizes. McGilchrist’s etymological threading of ‘true,’ ‘trust,’ and the Germanic *treu* supplies a philological bridge between these registers, arguing that truth itself is fundamentally a disposition of faithfulness rather than a propositional claim. The term thus holds in productive tension: cosmic sincerity, erotic commitment, institutional loyalty, and procedural compliance.