The Summary of Physics Restored

210Natural bodies possessing an active power and a hidden cause of action do not act through qualities alone, as is commonly supposed, but through hidden spirits. Fire does not heat or burn through the simple quality of heat, but through a continuous flow of spirits and rays. Neither earth nor water cools or moistens through the qualities of coldness and moisture alone: through fine vapours and inborn, emitted spirits they strike the senses even from a distance. Poisons likewise bring wasting and death, sooner or later, not merely through hot or cold qualities but through harmful spirits. The same judgement may be made about plants and herbs, because their active powers lie hidden not in their qualities but in their essence. Nature, whose foundation and powers chiefly concern spiritual things, has made this essence rich in spirits. Bodies are like shadows or garments of things, beneath which invisible Nature is concealed. Qualities, being accidents of things, cannot constitute their essence or unfold their wonderful powers in action. They are merely instruments of actions and affections implanted in matter, which the working spirits, or artificers of actions, also use when acting. Nature does not permit qualities to be the principles and efficient causes of actions.