Ancient Geographers and "Known Unknowns"


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“Reports that say that something hasn’t happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns — the ones we don’t know we don’t know.”  (Donald Rumsfeld, former Secretary of Defense)

With the news of the former Secretary of Defense’s new book appearing, entitled Known and Unknown, I was instantly reminded of the quote above. Many in the media at the time believed that this just added to a growing mountain of funny Rumsfeld quips.  I was also reminded, however, of a talk I gave here at the Library 2 weeks ago for CNU’s Latin Day to a group of young Latin students from around Hampton Roads. 

Since children do not devote an entire year or half-year to geography in the public schools anymore (as they did when I was a child, lo these many years ago), I decided that I would focus on our very strong collection of rare books representing the works of the Ancient geographers and those who continued commenting on their work up to the early 19th century.  Many of these Ancients believed that they were following in the footsteps of Homer, whom they considered the first geographer.  The work of Eratosthenes, whom we Moderns consider the father of geography, has only been preserved thanks to Strabo, a geographer from Asia Minor during the first centuries BCE and CE.  In Strabo’s book Rerum geographicarum libri XVII (G87.S8S5 Rare), he says that the function of the geographer is to be an interpreter, not of the whole world, but only of the inhabited world.  Every geographer after him considered that to be their task.

Eventually it became clear to geographers that there was land south of the equator that was inhabited, south of a torrid zone that was not, they believed, habitable.  Pomponius Mela, writing in 43 CE, described the “known world” (orbis situs) as being a sphere divided into 2 hemispheres, and that there were habitable zones both north and south of the torrid zone (Pomponius Mela cosmographicus de situ orbiz Hermolai Barbari fidelier emendatus (1501), G87.M5 1502 Rare). On the north side of the torrid zone was Africa and Eurasia.  On the south was a land he simply called “Antichthon”, (or Counter-Earth), inhabited by “antichthones”.  Mela knew there was something in the Southern hemisphere, he just didn’t know what it, or they, were.  16th-century maps interpreting or commenting on his work actually show a land mass south North Africa and south of an equatorial sea in the torrid zone called Antichthon.  It was a “known unknown”.

What completely surprised geographers of the 16th century was the existence of a continent to the West of Eurasia and Africa!  America first shows up in a chart from 1500 by Juan de la Cosa, captain and owner of Columbus’ flag ship Santa Maria (Carrack : 1492). America was most assuredly an “unknown unknown”.

So thank you, Mr. Secretary, for reminding us of the wisdom of the Ancients.