A 17th-century Ethiopian philosopher used pure reason to question every religion he knew

Hiding in a cave during a religious persecution in 1630s Ethiopia, Zera Yacob concluded that no single religious tradition could be trusted simply because it claimed divine authority — each contradicted the others, and each was just as sincerely believed by its followers. He argued that reason alone, not scripture or inherited custom, was the only reliable guide to truth.

— Zera Yacob, Hatata (Treatise of Zera Yacob) — written 1667