Conditional Reality

Prometheus had his liver pecked out because the Greeks thought the liver was the seat of intelligence. They believed the brain was a cooling apparatus for the blood. Or so we have been told. Surely there were some Greeks who heard voices in their heads, as we do, and recognized them as their own thoughts. Why is it we have not heard of these thinkers? Did they hide their beliefs out of fear? Or did keeping the secret give them a feeling of power? Or maybe they didn't think the whole issue was worth the debate. Will we ever know?