Saturday, June 12, 2021

Did Isidore of Seville Think the Earth is Flat? Yes, Probably.

Isidore of Seville (c.560 - 636) was one of the most influential authors of the early Middle Ages. Although he was a long-serving bishop, he wrote on secular subjects as well as religious ones. He’s best known for his Etymologies, an encyclopaedia in twenty books organised around word origins but covering a great deal more besides. He also wrote a guide to natural philosophy called On the Nature of Things. The sources that Isidore used for these works were wide-ranging, encompassing both pagan and Christian literature. While he was happy to mine pagan authors for useful information, he intended his books for a Christian audience seeking knowledge that was not remotely unorthodox. That meant that when his pagan sources conflicted with his Christian ones, he would almost invariably prefer the latter. But sometimes he must have found it hard to determine which side to favour. The shape of the earth was one area of uncertainty.

Historians have long known that medieval Europeans were well aware that the earth is a sphere. This runs contrary to the popular view that people in the Middle Ages thought the earth was flat until Columbus put them right. Medieval knowledge of the Globe is hardly surprising. It was the near-unanimous view of educated people in the Roman Empire that the earth was a sphere and large numbers of extant ancient texts from Plato and Aristotle in the four century BC to Macrobius and Martianus Capella in the fifth century AD state this explicitly. However, Isidore lived in a period when the western Roman Empire had collapsed and his native Spain was ruled by a barbarian dynasty of Visigoths. Isidore himself was instrumental in restoring knowledge of classical learning among the newly Christianised barbarian kingdoms but in his own lifetime that project was still a work in progress. Unlike the earlier pagan and Christian authors that he drew his knowledge from, he didn’t benefit from a secular education on philosophy and the liberal arts. To a great extent, he was an autodidact. We cannot simply assume that he imbibed ancient natural philosophy wholesale. On the question of the shape of the earth, there is very good evidence that he didn’t. Forty years ago, W.M. Stevens (Stevens, 1980) robustly defended the view that Isidore was a globalist, but more recent scholarship has swung the other way. In 1996, William McCready (McCready, 1996) found that Isidore is, at least, conflicted on this point while twenty years later, Andrew Fear stated “the notion of the flat earth runs throughout” Isidore's On the Nature of Things (p76 Fear, 2016).

Before we examine the text of Etymologies and On the Nature of Things in detail, we need to consider some foibles of the Latin language. The first is the word ‘orbis’. It’s natural to assume that this means orb, so if the earth is described as an ‘orbis’ that is tantamount to saying it is a Globe. But, although it could mean that, ‘orbis’ more usually means a disk. For example, Lactantius, a fourth century Christian writer who definitely thought the earth is flat, refers to the earth as an ‘orbis’ (Divine Institutes 3.23). Unfortunately, modern translators often render ‘orbis’ as globe, which, as well as being unclear linguistically, is very misleading. Also, like English, Latin mixes and matches the words for the earth (‘terra’) and the world (‘mundus’). It’s quite possible for ‘mundus’ to refer to either the earth or the whole universe. We just have to figure it out from the context.

It’s not controversial that Isidore thought the universe is a sphere and the earth is at its centre. He drew much of his cosmological knowledge from a book called Astronomy by Hyginus (d. c. 17AD). Unfortunately, this book is more concerned with the myths behind the constellations, but begins with a brief primer on cosmology. It is also clear that Isidore did not believe there are any antipodeans, that is people who live on the other side of the world. Indeed, he said this was physically impossible as “neither the solidity nor the central space of the earth allows this.” (Etym. IX:2.133) However, none of this tells us whether the earth itself is a globe.

Some of the key passages are in book XIV of Etymologies. Isidore started by telling us the the earth (‘terra’) is at the centre of the universe equidistant from all other parts (this is pretty much a verbatim quote from Hyginus). He then noted that ‘terra’ in the singular refers to the whole ‘orbis’. Now ‘orbis’ could be sphere or disk, but Isidore helpfully sorted out this confusion in the next paragraph. “Orbis” he tells us, “derives its name from the roundness of the circle, because it resembles a wheel.” (Etym. XIV:1.2) That seems clear enough, but then he muddied the waters by quoting from Hyginus again: “The ocean that flows around [the orbis] on all sides encompasses its furthest reaches in a circle.” Then he notes that the ‘orbis’ is split into three continents - Asia, Europe and Africa. Now, if the ‘orbis’ refers to the whole earth, this is a pretty accurate description of the traditional Greek world picture that imagined the earth was a flat disk, girt by water and containing three continents arranged in a circle. However, in the fourth century, Aristotle explained that the earth is actually a sphere so the three continents became the inhabited world (‘oikemene’ in Greek) occupying a band of the earth’s sphere. The ‘oikemene’ was still generally thought of as round, which irritated Aristotle who thought it was actually a strip across the face of the globe, not a circle. 

As for Isidore, he was clear in Etymologies XIV:2 that ‘orbis’ means a circle, not a sphere. Since he describes the earth itself as an ‘orbis’ in XIV:1, we can reasonable conclude he thought it was a disk. It is worth noting that while Isidore described the heavens with the unambiguous Latin word ‘sphera’, he never used this to describe the earth. He never called it a ‘globus’ either. Something else missing from Isidore is the standard pieces of evidence that the earth is spherical. Classical authors from Aristotle onwards used various combinations of arguments to show the earth is a globe, for example that we cannot see southern stars from the northern hemisphere; the shadow of the earth at a lunar eclipse is curved; or a mountain disappears below the horizon as we sail away from it. Isidore had access to these arguments from his reading of Macrobius and Pliny, yet he never mentioned them. If Isidore really did think the earth was a sphere, he also thought it was so blindingly obvious that he didn’t need to provide any evidence. This is in marked contrast to Bede, writing perhaps a hundred years later who was completely unambiguous: “It is, in fact, a sphere set in the middle of the whole universe. It is not merely circular like a shield, or spread out like a wheel, but resembles more a ball, being equally round in all directions.” (On the Reckoning of Time 32) His insistence that the earth is not like a wheel sounds like a direct rebuke of Isidore, whose work he knew well. Bede went on to provide evidence from Pliny that the bright southern star Canopus is not visible to the north and the length of the day depends on latitude.

There is further evidence of Isidore’s views in the diagrams and maps that accompanied his works. The most famous is the T-O map showing the continents of Asia, Africa and Europe in a circular stylised form. These maps may not have originated with Isidore, but certainly propagated widely by being included in his work. In fact, they remained popular right up until the fifteenth century when Europeans’ encounter with the Americas made them obsolete. That’s to say, they remained in use long after every literate person in Europe knew the earth was a sphere. They were interpreted as maps of the ‘oikemene’ and were sometimes even shown on a face of a globe. However, Isidore’s work lacks the additional context on the earth as a whole being a sphere so any reader coming fresh to his text would obviously assume the T-O map showed a flat earth. 

Isidore: TO map

Isidore also provided his own take on the climatic zones enumerated by numerous classical authors. The zones are formed by the projection of great circles in the heavens onto the surface of the earth. For instance, the tropics of Cancer and Capricorn are the maximum distance the sun moves north and south of the equator over the year. Projected onto the earth, the tropics bound the torrid zone of great heat. Macrobius provided a useful diagram of the Globe divided into five bands - the arctic and antarctic are at the top and bottom, then the habitable zones of the northern and southern hemispheres. Finally, the tropics stretch around the equator. Isidore thought the heavens were spherical, so accurately explains how the five zones are delineated by great circles in the sky. But he also thought the earth was flat, which made a nonsense of projecting the circles down to the ground. As a result, he ended up arranging the climate zones into a ring, with the arctic and antarctic next to each other. (On the Nature of Things 10). It is strange he would have done this, rather than presented the diagram of Macrobius (see below), if he thought the earth was a sphere. 

Isidore: climatic zones in a ring

Ultimately, the fairest reading of Isidore is that his cosmology was similar to that of the presocratic philosopher Anaxagoras, who said a flat earth is found at the centre of a spherical universe, supported by a cushion of air. (Isidore himself wondered whether the earth was held up by air or water (On the Nature of Things 45)). To read him otherwise requires us to interpret his work in a way that assumes we have already proved he must support the Globe.

There are various reasons that scholars, including such significant figures as Faith Wallis and Marina Smyth, have assumed that Isidore rejected the flat earth. An obvious one is that it was clearly set out in his sources. However, while pagans like Pliny and Hyginus certainly did say the earth is a sphere, Christians such as Augustine and Ambrose, both read carefully by Isidore, equivocate about the point (even though they probably knew it too). The Bible’s authors also assumed the truth of ancient flat-earth Babylonian cosmology. Where there was a conflict between pagan and Christian sources, it is not surprising that Isidore favoured the Christian interpretation. Another reason is Isidore himself was frequently incoherent. He quotes the likes of Hyginus without necessarily twigging that these words might not make sense outside the context of the Globe. But Isidore’s own words, as opposed to quotations from earlier authors, don’t betray a spherical view. He always wrote as if the earth is flat. It is hardly surprising that excerpting manifold authors over many years meant that Isidore committed the occasional infelicity. One such case is Etymologies XIV:5 where he noted in passing that there was a fourth continent “further inland towards the south”, thus contradicting himself and providing support for those who say the flat ‘orbis’ of Etymologies XIV:2 is the inhabited ‘oikemene’ only and not the entire earth.

Macrobius: climatic zones on a globe 

Ultimately, though, I think the misreading of Isidore comes down to two points. One is the understandable desire to debunk the myth that everyone in the Middle Ages thought the earth was flat. Some authors (myself included) have been unwilling to concede that in the early Middle Ages, knowledge of the Globe had to be rediscovered and disseminated before it became widely accepted. Thus we have been too defensive of Isidore, who wrote at the cusp of the transition from ancient to medieval scholarship (p97 White 1993). Finally, alas, we’ve made the understandable mistake of translating ‘orbis’ as orb and not as disk. Once we get that right Isidore, although mistaken about the shape of the earth, at least starts to make rather more sense. 


Bede. The Reckoning of Time. Translated by Faith Wallis. Liverpool: Liverpool University Press, 1999.

Bede. On the Nature of Things. Translated by Faith Wallis. Liverpool: Liverpool University Press, 2010.

Fear, 2016: Fear, Andrew. “Putting the Pieces Back Together: Isidore and De Natura Rerum.” In Isidore of Seville and His Reception in the Early Middle Ages, edited by Andrew Fear, and Jamie Wood, 75–92. Amsterdam: Amsterdam University Press, 2016.

Isidore of Seville. The Etymologies of Isidore of Seville. Translated by Stephan A. Barney. Cambridge: Cambridge University Press, 2006.

Isidore of Seville. On the Nature of Things. Translated by Calvin B. Kendall, and Faith Wallis. Liverpool: Liverpool University Press, 2016.

McCready, 1996: McCready, William D. “Isidore, the Antipodeans, and the Shape of the Earth.” Isis 87, no. 1 (1996): 108–27.

Stevens, 1980: Stevens, WM. “The Figure of the Earth in Isidore’s ‘De Natura Rerum’.” Isis 71, no. 2 (1980): 268–77.

White 1993: White, Andrew Dickson. A History of the Warfare of Science With Theology in Christendom. Amherst: Prometheus Books, 1993.

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