This text critically examines the traditional conception of inertia as an inherent property of material bodies reacting solely to external physical forces. The author argues that such a definition is incomplete, as it neglects internal dynamics and the priority of sense or purpose over mere persistence. A fundamental distinction is proposed between inertia and mass, supported by examples from chemistry and nuclear physics, such as radioactive decay, where stability varies independently of mass. Furthermore, the text distinguishes between the intrinsic inertia of physical objects and the intended permanence of ideal entities, such as geometric shapes, whose constancy is guaranteed by the active subjectivity of thought. Finally, the author challenges the notion of absolute stillness, noting that even seemingly static matter is characterized by constant internal motion at the atomic level. This reflection seeks a more nuanced ontological understanding of the relationship between matter, motion, and intentionality.