The provided text examines René Descartes' dualism and its impact on traditional ontological thought. Descartes introduced the concept of two finite substances alongside a single infinite substance, a move that significantly challenged and redirected the prevailing philosophical discourse of his time. While acknowledging the effectiveness and historical success of this framework, the text highlights a fundamental flaw inherited from earlier traditions: the ontological definition of substance itself. This conception views substance as a rigid, unchanging foundation upon which external changes occur, rather than something more dynamic. The author suggests that while Descartes was instrumental in shifting philosophical paradigms, his reliance on this static notion of substance burdened his system with a significant conceptual error. This critique underscores the tension between Cartesian innovation and its adherence to problematic traditional metaphysical assumptions, questioning whether the shift he initiated was entirely positive for the long-term development of ontological theory and understanding.