In section 5 of Discourse on Method by Descartes he talks about the difference between beasts and humans. He starts off by saying that if there were a machine with the same organs as a beast, that it would be indiscernible from the actual animal. But if there were a machine with the same organs as a human, we would notice the difference. According to Descartes there are two major reasons why we would be able to notice the differences between the human machine and the human, and not the animal machine and the animal.
The first reason is that the human machine would not be able to communicate in the same way as we humans do. The machine, of course, could react to normal stimuli such as a hot poker being pushed into its side, but when it comes to more complex wording such as expressing one’s feelings, the machine cannot do this. The animal and its machine behave in the same way. Even though an animal can repeat human phrases, they cannot speak the language. Just as the machine could repeat human phrases and even speak the language, but they would not be able to express themselves in their own way.
The second reason is that the human machine lacks a rational soul. So even though they might be able to do certain tasks as well or better as humans, the machine can only do those tasks. They lack knowledge; they can only do what they are programmed to do. Animals are the same as their machine, because they act through the disposition of their organs. They don’t think, they eat when their stomach tells them too, sleep when their brain tells them to, and urinate when their bladder tells them too. An animal machine with these same organs would act in the same way as the animal. While a rational human would be able to look at a situation and act depending on how they feel. And different people will act in different ways, unlike the machines that will all act the same way.
Personally I disagree with Descartes