like the brain is literally encased in the body so how can it be separate? like if you go around licking lamp posts you’re going to pick up some germ that’s gonna make you feel like crap and you get insomnia or fever and your brain will definitely be impacted. and so you’ll have short temper and that’ll get you into trouble.
I once read that the Romans didn’t really understand what the brain was for, and believed that thoughts and emotions emanated from the heart. They certainly saw enough warfare and bloodshed to know that a massive head wound/ brain injury was fatal, but didn’t really understand its purpose.