Res Cogitans

Descartes argued that res cogitans—thinking substance—requires absolutely no extension in space to exist, making it fundamentally different from physical matter. This creates a bizarre ontological puzzle: if your thoughts truly occupy zero cubic centimeters, where exactly are they when you're thinking about pizza? The implications are wild—it suggests consciousness could theoretically exist in a mathematical point, or nowhere at all, yet still be perfectly real.

In 1643, Princess Elisabeth of Bohemia asked Descartes the question that still haunts philosophy: if mind and body are completely different substances, how does your immaterial thought make your material arm move? Descartes fumbled badly, eventually invoking the pineal gland as a meeting point—which didn't solve the problem at all. Her letters reveal she wasn't just poking holes; she was doing serious medicine for chronic illness and needed to understand how psychological stress affected her physical body, making this arguably the first psychosomatic medicine debate.

Today's AI debates are essentially asking: does ChatGPT have res cogitans, or is it just fancy res extensa—elaborate matter shuffling? The Cartesian framework forces us to decide if consciousness requires some non-physical "thinking stuff" that machines can't have, or if thinking is just what sufficiently complex physical systems do. Your intuition about whether AI can truly "think" likely reveals whether you're a secret Cartesian dualist or a materialist who believes consciousness emerges from arrangement of matter alone.

If res cogitans is truly immaterial and separate from the body, anesthesia presents a philosophical crisis: how can physical molecules switch off something that exists outside physical reality? The fact that propofol reliably erases consciousness by affecting brain chemistry is probably the strongest everyday evidence against Cartesian dualism. Yet we still talk about consciousness as if it's something independent—when you say "I have a body," who is this "I" that possesses it?

Some modern philosophers and physicists have tried to resurrect res cogitans through quantum mechanics, suggesting consciousness collapses wave functions and therefore plays a real causal role in physical reality. This would make mind a fundamental force like gravity or electromagnetism—immaterial but physically potent. Most physicists find this unconvincing, but it shows how desperately we want Descartes to be partly right, because accepting pure materialism means accepting that "you" are just arrangements of atoms that happen to feel like something.

Notice how you say "my brain" rather than "me, the brain"? Or how you claim to "have" a body rather than "be" one? We speak like Cartesian dualists even if we intellectually reject dualism, revealing how deeply res cogitans has colonized our language and self-concept. This linguistic habit has real consequences: it makes us neglect physical health as if it's separate from mental wellbeing, and treat our bodies as vehicles we pilot rather than the totality of what we are.