The Treatise on Man opens with a famous metaphor: Descartes compares the human body to a machine created by God. This machine has an external and an internal part. The external part is matter, a machine made of earth. The internal part has different pieces, with different functions, which proceed from matter and are possible because of the disposition of the organs. In a letter to Reneri in 1638, however, Descartes distinguishes between the God-made machine and the man-made automaton. Are machines and automata synonyms or is there a “mechanical” difference between a machine and an automaton? The aim of this paper is to explain the functioning and the role of some devices and machines to prove that all machines are not automata and not all automata are machines. Firstly, I will analyze the difference between machines and automata and then show what Descartes considers a machine and in which cases he uses the term ‘machine’. Secondly, I will examine some specific devices such as fountains, mills, orgs, and clocks to sharpen the “distinction” between machines and automata. Finally, the concept of automata will be described and explained. By doing so, I can work out which category the human body fits into.