Marsilio Ficino’s Platonic Theology, Volume I

A body does nothing by its own nature.

1Since, for Plato, body consists of a certain matter and quantity, while it belongs to matter alone to be extended and affected—and extension and affection are themselves kinds of passivity—quantity either is nothing other than matter's own extension or, if it is something else, is at any rate a thing of such a kind that it is always subject to division, subjects matter to every ensuing affection, and pours nothing into foreign matter. It follows that body itself, precisely as body, performs no action at all, but is subject only to being acted upon.

2The same conclusion is also clear from the fact that three conditions above all are required for any natural action to be perfect. First, the agent must be supremely powerful in itself; second, maximally ready for motion; third, it must easily penetrate the patient, and the patient itself must be united as closely as possible with the agent. Bodily bulk seems to obstruct all three. First, because it extends through very many parts, the active power within it is dispersed, far removed from itself, and drawn apart to the greatest possible degree. Power is increased by union just as it is diminished by dispersion. Thus dryness strengthens the force of both heat and cold because it unites it, whereas moisture weakens that force because it disperses it. Next, the larger a body is, the more sluggish it is in itself and the less suited to motion. Accordingly, the more a body increases, the more it retards motion and delays action. The force of lightness, for instance, lifts a spark upward more quickly than a flame; the force of gravity draws a piece of wood downward more quickly if it is pointed than if it is broad. Finally, since every body fills its own place and one place cannot contain two bodies, bodies cannot merge into one. Their solidity and density also prevent them from penetrating one another. Thus the distance between parts weakens the power to act; largeness of bulk retards motion; thickness obstructs the penetration of bodies. Worse still, if Nature compresses the scattered parts of a body to increase its power through union, the body itself becomes thicker in the process and less able to enter. But if Nature rarefies it to obtain ease of motion and penetration, the power to act is immediately dispersed.