The concept of inertia was alien to the physics of Aristotle. Aristotle, and his peripatetic followers held that a body was maintained in motion only by the action of a continuous external force. Thus, in the Aristotelian view, a projectile moving through the air would owe its continuing motion to eddies or vibrations in the surrounding medium, a phenomenon known as antiperistasis. In the absence of a proximate force, the body would come to rest almost immediately.