Description This paper develops the third a priori condition of SAE epistemology: must-have-cognitive-direction. It argues that lossy compression's cost must not be wasted, therefore direction is necessary — making each round of loss yield returns. Direction transforms the flywheel from compelled spinning into purposeful movement, but once direction solidifies, the flywheel becomes a rut (the direction wall). The paper uses Apple as the paradigm case, distinguishes 14DD direction (living judgment) from 12DD direction (dead inertia), and argues that the direction wall cannot be broken from within — providing the necessity argument for the fourth condition (must-be-questioned). Bilingual: Chinese original + independent English rewrite. SAE Epistemology Series Paper 3 of 4. Keywords cognitive direction; direction wall; flywheel; purpose; Apple; iPhone; paradigm; Kuhn; information bottleneck; dimensional sequence; Self-as-an-End; SAE Resource Type Publication / Preprint License CC BY 4.0 Language zho (Chinese), eng (English) Related Identifiers Is part of series with: SAE Epistemology Paper 1 (DOI: 10.5281/zenodo.19502952), Paper 2 (DOI: 10.5281/zenodo.19503017), Paper 4 (DOI TBD) References: 10.5281/zenodo.19502952 (SAE Epistemology Paper 1) References: 10.5281/zenodo.19503017 (SAE Epistemology Paper 2) References: 10.5281/zenodo.18528813 (SAE Foundation Paper 1) References: 10.5281/zenodo.18666645 (SAE Foundation Paper 2) References: 10.5281/zenodo.18727327 (SAE Foundation Paper 3) References: 10.5281/zenodo.19329284 (Beyond Fast and Slow) Subjects Philosophy of Mind, Epistemology, Artificial Intelligence, Organizational Theory, Cognitive Science