Tilly: Leibniz's theory

Leibniz examined the premises of the new science and found that they were inadequate. He felt that even physical facts could not be satisfactorily explained by the hypothesis of expansive objects and motion alone. Descartes once taught that momentum is constant. But the object enters stationary, and the object begins to move again: the motion seems to be lost and then gained. This would violate the principle of continuity, that is, nature does not make jumps. When motion stops, there must be something that continues to exist, the basis of motion: force, or nature, or the tendency of objects to move or to keep moving. Thus, all solid beings are active, all are manifestations of force: what is inactive is what does not exist; only what is active is real. In this way, the essential property of matter is force rather than extension. In the same way, the law of immortality of motion must give way to the law of immortality or conservation of energy. Another evidence that expansiveness is not the essential property of an object lies in the synthetic nature of expansiveness: anything composed of parts cannot be primordial origin. There is a need for something simple, and force is such a simple, indivisible reality.

In Leibniz's philosophy, the geometric or static concept of nature was replaced by the view of dynamic or energetic. Objects do not exist by extension, but by objects or forces; without force, without dynamic objects, there is no extension. In Descartes' view, the existence of objects presupposes expansiveness; in Leibniz's view, expansiveness presupposes the existence of objects or forces. Force is the "source" or source of the mechanical world, which is the perceptual representation of force. "Extension presupposes a property, attribute, or essence in an object that stretches itself, expands outward, and perpetuates itself." There is a force in the object that precedes all expansiveness. Because of the resistance in the object, the object appears impenetrable, finite, or material. Every unit of force is an inseparable union of soul and matter, active and passive; it is a purposeful, organized, self-determined force that also limits itself, or rather has an resistive force.

Space, therefore, is seen by Leibniz as the result of the harmonious coexistence of forces; since space does not have an absolute existence, there is no absolute space in which things exist, but space is related to things, and without things, space disappears. Force does not depend on space, but space depends on force. Thus, there is no void space between and outside things: where forces cease to function, the world will also perish.