Abstract

Leibniz considered that there are substances in a body, each of which does not solely have a shape and size and can act spontaneously. Although he started to regard bodies as having inherent substantial forces in 1678–79, what exactly led him to suppose this is not obvious. The author aims to articulate Leibniz's most important motivation for "restoring" substantial forms. He first notes that Leibniz considered that every body tends to slow down because of its natural inertia. He then discusses that Leibniz had two arguments to postulate the existence of substantial forms, the first of which is based on his view that God providentially manages the universe in the most efficient way. The second and more interesting argument is based on Leibniz's understanding of science, according to which a scientific explanation of motion should be given in terms of the nature of the body.