Res extensa

there were disagreements on the divisibility of the atom and on the nature of space.

Descartes posited a radical dualism in which the world has two mutually exclusive aspects, res cogitans and res extensa.

This is so-called mind-body dualism.

The mind, the soul, anything that has no physical property, yet still exists, is part of the res cogitans, which is simply Latin for thinking thing.