answer:In this context, you’re mixing up the physical heart (blood circulation organ) with the metaphorical heart. As far as why the heart has a metaphorical meaning these days, well, it’s been that way for a long time. We didn’t start this particular fire. ;) Back in the day, the Egyptians didn’t know what the brain was for. It wasn’t as clear as, say, the stomach that held food or the heart that pumped blood. Mostly they thought the brain is what made snot, and it was so useless in the afterlife that they discarded it when mummifying a corpse (but they kept other, important organs in jars for you). However, perhaps they noticed the way that the “heart” pumped more when excited, or seemed to beat more slowly when asleep, and when the heart stopped beating entirely, someone looked like they didn’t feel anything at all. So when you were looking to enter the Egyptian afterlife, you needed to have a “light” heart (when weighed against a feather) – that is, one not burdened by troubles and misdeeds. The “heart” has been the center of emotion for a long time. It’s a myth that is so potent, it can overrule actual medical knowledge – which is really not so different from some religious beliefs today.