I am a thinking thing, and I express my thoughts in language. Other thinking things express their ideas in language. Therefore , all thinking things express their ideas in language. Animals, though they make noise and can imitate words and phrases, do not express their ideas in language. The Argument from Reason - P1.
Human beings are rational minds joined with bodies.
Therefore , it is the rational mind and not the various machine parts that enable humans to do the many different kinds of things they do. Any machine which does not exhibit rational thought in its behavior is not a thinking thing. Animals and automata, though their bodies are composed of similar kinds of parts as the human body, do not demonstrate rational thought in their behavior. There are, of course, several important points to highlight about Descartes' three arguments. First, if he's right, animals are nothing more than biological machines different from mechanical automata only in they are fashioned by God and not humans, and their bodies are organic.