Force is one of the most fundamental concepts in physics, yet its ontological status remains contested. Newtonian mechanics treats it as the cause of changes in motion; field theory expresses it as the gradient of a potential or field; general relativity geometrizes gravity. These theories provide highly successful calculational frameworks but do not directly answer, at the same level, what force is. Starting from the first principles of Energy-Efficiency Theory (EET), this paper proposes a more cautious ontological reinterpretation: force can be understood as the directed response of a constrained-state energy structure to a free-state energy gradient. In this framework, mass, charge, magnetic moment, and more generally stable structures are treated as different forms of constrained-state energy; gravitational fields, electric fields, magnetic fields, and more generally external drives are treated as manifestations of free-state energy distributions and their gradients. Force is thus no longer taken as an independent entity but is reinterpreted as the response component within a "source–gradient–response" structure. A schematic unifying relation F ∝ ρc · ∇Ef is introduced to express this unified picture, and its interpretive compatibility with gravity and classical electromagnetism is discussed. For strong and weak interactions, a more cautious higher-level ontological reading is offered. It is emphasized that the proposed unifying relation is primarily an ontological and phenomenological schematic relation, not a universal computational formula that replaces existing dynamical equations for interactions within this paper. Several operational consequences and heuristic test paths are proposed, aimed at comparing, within matched systems, the relationships among constraint strength, external gradient, and response structure.
Hongpu Yang (Thu,) studied this question.