Cosmas Indicopleustes

Cosmas was an Alexandrian merchant who spent his working life at sea. He sailed the Red Sea and the Persian Gulf, traded along the coast of East Africa, and went inland into the kingdom of Axum in what is now Ethiopia. His nickname, Indicopleustes, means "the one who sailed to India" and whether he actually reached India or only its trading partners is argued; he certainly knew people who had.

At Adulis, the port of Axum, around 525, the local governor asked him to copy out two ancient Greek inscriptions before they were lost. He did, and his copy is the only record of them that survives. That is the kind of man he was, a trader with a scholar's habits.

Later he became a monk, and around 550 he wrote the Christian Topography in twelve books.

The book has two halves, and they pull in opposite directions. The famous half is an argument that the earth is not a sphere. Cosmas held that the universe is shaped like the tabernacle Moses built: a rectangular box, with the flat earth as its floor, the heavens as a vaulted lid, the sun circling behind a great northern mountain to make night. He wrote against the Greek astronomers on principle, believing their sphere could not be squared with Scripture.

Educated Byzantines did not follow him, Photius, reading him three centuries later, called the doctrine absurd, and the sphericity of the earth remained the standard view among learned Christians throughout the Middle Ages. Cosmas was an outlier in his own time, and later writers who claimed the medieval church taught a flat earth leaned on him precisely because he was unusual.

The other half is priceless. Cosmas describes the trade routes of the sixth century in detail: the silk coming overland from China, the pepper and spices of Malabar, the pearl fisheries, the coinage, the customs. He reports Christian congregations already established in Ceylon and on the Malabar coast of India with clergy ordained from Persia, and Christians in Socotra and among the Huns, hard evidence that the church of the East had reached the Indian Ocean well before the sixth century. He describes the court of Axum and the elephant hunts of Ethiopia.

He appears to have belonged to the Church of the East himself, and to have been taught by Mar Aba, its patriarch. The oldest manuscripts of his book carry his own maps and drawings.

Sources: Cosmas Indicopleustes, The Christian Topography, translated by J. W. McCrindle (Hakluyt Society, 1897); Photius, Bibliotheca, codex 36; The Catholic Encyclopedia (1913), s.v. "Cosmas Indicopleustes".