Abstract

There are two axes of Leibniz’s philosophy about bodies that are deeply inter- twined, as this paper shows: the scientific investigation of bodies due to the application of mathematics to nature – Leibniz’s mixed mathematics – and the issue of matter/bodies ide- alism. This intertwinement raises an issue: How did Leibniz frame the relationship between mathematics, natural sciences, and metaphysics? Due to the increasing application of mathe- matics to natural sciences, especially physics, philosophers of the early modern period used the reliability of mathematics to predict phenomena as the basis to infer the metaphysical outlook of nature. I argue that although Leibniz thought metaphysics must be scientifically informed and that mathematics is a valuable instrument to understand nature, metaphysics is more fun- damental than mathematics and natural sciences. By highlighting the foundational relation be- tween metaphysics and the sciences, this paper showcases an argument for the reality of bodies: the ideality of bodies, necessary for epistemic purposes, is not proof that they are not real. Keywords: Metaphysics, Application of Mathematics, Body, Idealism, Fundamentality.