Although Descartes set up the stage for a metaphysical explanation of existence, not everyone accepted his mind-body dualism. In 1949, Gilbert Ryle made the famous argument against dualistic philosophy in his work The Concept of Mind. He believed that there were two kinds of substance: physical and non-physical. Ryle dismissed the notion of an immaterial mental substance separate from a physical one as ‘the ghost in the machine’, the result of a categorical mistake.
The physical substance cannot be thought of as something separate from us because we think with our brains. We think with our bodies, not with our minds. Our experience consists of our brain sending signals to our body which sends back signals to our brain. There is no reason to believe that these signals aren’t real—they’re what constitutes our consciousness. If you ask me whether I’m hungry, my answer will be a signal sent to my stomach. My stomach sends a signal to my brain telling it whether or not I am hungry—this is what constitutes my subjective experience of hunger. So even though I may say that I’m hungry, my statement isn’t true. Food does not really exist until after it reaches my mouth and enters my digestive tract and becomes digested. Therefore, it doesn’t matter if I believe that there is something called “hunger” out there in nature. It doesn’t exist. There are just thoughts and feelings inside my head.
He argued that considering this system, metal reality and physical reality must belong to the same category, refuting otherwise would be the same as considering the stomach and the idea of hunger as separate ghostly entities.
