Does thought come from the heart or the head?

That time, that place

Alexandria. In the Greek world, cutting open a corpse had long been forbidden. Egypt was different: a tradition of mummification left less horror at handling the body's interior. Under Ptolemaic patronage, a brief window opened in which the human body could actually be examined from within.

Why this question

A great dispute was under way: does thought and sensation sit in the heart or in the head? Aristotle said the heart. It is warm, it beats, it responds when you are frightened or in love. The brain, he thought, merely cooled the blood.

What was found

Herophilus opened the body and looked. He traced thin cords running from the brain through the body, and distinguished those serving movement from those serving sensation. Thought and feeling, he concluded, are centered in the brain.

Nor was that all. He found that arteries and veins differ in the thickness of their walls, and that the pulse is caused by the beating of the heart. Names he gave — the retina, the duodenum — are still in use.