Abstract

Aristotle's rule of proportions of the factors of motion, presented in VII 5 of the Physics, characterizes Aristotelian force. Observing that the locomotion to which Aristotle applied the Rule is the motion produced by manual labor, I develop an interpretation of the factors of motion that reveals that Aristotelian force is Newtonian power. An alternate interpretation of the Rule by Toulmin and Goodfield implicitly identifies Aristotelian force with Newtonian force. In order to account for the absence of an acceleration in the rate of forced motion, they incorporate into the Rule the medium's resistance to motion due to viscosity as an additional factor. The resulting interpretations of the original factors of motion lose the exactness the power interpretation grants them. The constant rate of forced motion follows immediately from the power interpretation. It is also compatible with the Rule's description of the motion that is produced by the sum of forces