This book presents a recasting of Aristotle's theory of spatial
displacement of inanimate objects. Aristotle's claim that projectiles
are actively carried by the media through which they move (such as air
or water) is well known and has drawn the attention of commentators from
ancient to modern times. What is lacking, however, is a systematic
investigation of the consequences of his suggestion that the medium
always acts as the direct instrument of locomotion, be it natural or
forced, while original movers (e.g. stone throwers, catapults,
bowstrings) act indirectly by impressing moving force into the medium.
Filling this gap and guided by discussions in Aristotle's Physics and On
the Heavens, the present volume shows that Aristotle's active medium
enables his theory - in which force is proportional to speed - to
account for a large class of phenomena that Newtonian dynamics - in
which force is proportional to acceleration - accounts for through the
concept of inertia. By applying Aristotle's medium dynamics to
projectile flight and to collisions that involve reversal of motion, the
book provides detailed examples of the efficacy and coherence that the
active medium gives to Aristotle's discussions. The book is directed
primarily to historians of ancient, medieval, and early modern science,
to philosophers of science and to students of Aristotle's natural
philosophy.