Duhem, Pierre. To Save the Phenomena: an essay on the idea of physical theory from Plato to Galileo (trans. Edmund Doland and Chaninah Maschler; Chicago: University of Chicago Press, 1969).
This is a classic work of philosophy of science, incorporating ideas first published by French physicist Pierre Duhem in 1908. He was widely read in the history of science, and in the content translated here studies the long legacy of a concept first emerging with Greek philosophers such as Posidonius and Simplicius, and to some extent in Plato, certainly his later advocate Proclus, but opposed by Aristotle. The idea is that the astronomer, and we could read here any physical scientist, is simply trying to offer hypotheses that explain what is observed about the natural world, in this case the movement of the planets in the heavens. The opposite is to claim that the hypothesis one offers to explain and integrate such observations corresponds to ‘the way things are’ – which is to adhere to ‘realism’. Greek philosophy was as a rule sympathetic to the goal of simply offering explanatory models that didn’t claim to be ‘real’ or explain true causes, because they mostly believed that the heavens, from the moon’s orbit and upwards, was fundamentally different to the terrestrial (earthly) sphere and so in principle could not be grasped by human thought. It was the realm of God or the gods, and they alone knew how it truly worked. Someone like Ptolemy, most importantly, was happy if he could offer a geometrical model that might explain the way the ‘planets’ (among which they counted the sun and the moon) moved. They debated whether such models should depend mostly on elliptical orbits around the earth, or instead, circular orbits around which planets moved while themselves orbiting ‘epicycles’, a compound cyclical motion that seemed truer to the fundamentally circular nature that seemed appropriate to heavenly motion. A few proposed that the earth itself might move, but that wasn’t the general mood.
Duhem shows (or claims), most interestingly, that around the time of Copernicus, many astronomers still acknowledged this principle that they were obliged simply to offer a mathematical model that explained planetary paths. Some Aristotelians in the Averroist tradition, called Peripatetics, maintained a realist view instead. Copernicus himself, claims Duhem, was a true realist, and believed that his new heliocentric theory (following the minority classical antecedents) actually represented the true realities of the cosmos. This was a little unusual at the time, and even the anonymous author of the preface to Copernicus’ groundbreaking De revolutionibus (1543), in which his new model was published, heads in exactly the opposite direction, presenting Copernicus’ theory as a mere model, intended only to ‘save the appearances’. Duhem cites another astronomer as revealing the writer’s identity as the well-known Osiander. Copernicus’ proposal was rather popular among astronomers early on, and not too controversial in that most took it as simply a model, such as Osiander. It even acted as the mathematical background for the Gregorian (i.e. papal-sponsored) reform of the calendar in the 1580s. But realism was on the rise, and Duhem uses this to help explain why Giordano Bruno and especially Galileo got in trouble with the Catholic church. By insisting that the Copernican model was not just a mathematical help for astronomy but represented cosmic realities truly, they forced it to impinge on the territory of natural philosophy, concerned with real causes. In the day, this meant it confronted both Aristotelian metaphysics, which was fundamentally geocentric, and biblical statements that seemed to speak of the earth’s fixity. And it was compatible with neither.
So Galileo probably could have co-existed with church authorities had he been a non-realist, offering simply to ‘save the phenomena’. It was his stout realism that got him into trouble! But Duhem points out that he and his colleagues, even Tycho Brahe in offering a compromise claim, effectively unified physics by seeking common explanations for the movements of heavenly and earthly things. No longer would the heavens be seen as fundamentally incomprehensible. It was game on for modern astronomy.
Russell, Jeffrey B. Inventing the Flat Earth. New York: Praeger, 1991.
This is one of those books I heard I ought to read, but took a while to find and get around to. It’s an entry in the genre, history of ideas. Specifically, it rebuts the idea that most Christian thinkers since earliest times thought the world was flat, and that it was Columbus who proved it wasn’t by not sailing off the edge of it. More broadly, in removing this linchpin, he rebuts the more vague, general concept that the blind dogmatism of Christian theology has been largely responsible for resisting the progress of knowledge, e.g. revealing the roundness of the earth, soon to be followed by Galileo’s breakthrough in backing Copernican heliocentrism against the Church.
The key piece of evidence against this idea is that many leading (late) medieval Christian thinkers were Aristotelian, e.g. Thomas Aquinas, and that Aristotelian cosmology was fundamentally spherical, with earth at the centre, surrounded by a whole series of mobile ‘shells’ that carried the successive planets in their orbits about it. It was premised on the differing ‘weight’ of the elements of earth, water, air and fire, so that the heaviest, earth, must inevitably settle to the centre. There was no more efficient concentration of earth in the centre of the cosmos than a sphere.
Russell mentions a practical illustration of the prominence of a spherical view of the earth during the Middle Ages – kings’ orbs symbolizing their worldly dominion…in the shape of spheres. He can cite plenty of examples of overt references to the sphericity of the earth, and shows that most actual references to primary sources come eventually down to the Latin church father Lactantius and the Eastern Alexandrian writer Cosmas Indicopleustes. Both are authentic flat earthers, and Cosmas’ sixth-century Christiana Topographia explains the world as a rectangle on the model of the tabernacle floor plan. It is indisputably flat earth, but what is disputable is just how widespread such a view of the world was, then and afterwards.
Russell makes these two figures seem like exceptions to the rule of a mostly better-informed Christendom, along the way conceding that the eastern father Severian was another flat-earther and that others like Basil the Great prevaricated, feeling torn between philosophy’s support for a spherical earth and apparent biblical support for a flat one. On the other hand, philosophically astute thinkers like John Philoponus were apparently embarrassed by Cosmas’ cosmology and sought to refute it in favour of a philosophially robust Christianity.
Russell’s historical protagonists are above all the ‘creative’ C19th historical writer Irving Washington and the Frenchman Antoine-Jean Letronne (1787–1848), both filtered especially through the sceptical Andrew Dickson White, the writer who above all others established the sense of conflict between science and religion in popular culture. The difference between Russell and those opposite is essentially that for them the church, with its vast majority of unknown opinions, is guilty of obscurantism until proven innocent, and for Russell it is innocent until proven guilty.
My sense is that the flat earth idea is mostly erroneous, as Russell proves, and that in educated circles there was no doubt well prior to Columbus that the earth was a sphere. But I am a little cautious regarding the Eastern church in the patristic era. Russell mentions that Diodore of Tarsus was reproved by Photius for being flat-earth, and Theodore of Mopsuestia is suspected of having viewed the world the same way. This helps to explain Severian’s stance shortly afterwards. I have read other Eastern and Syrian treatments where the firmament is treated very literally as a dome covering the earth, and I suspect that a flat-earth understanding may have been rather widespread in the Eastern and Syrian churches late in the patristic period.
But not so later. The medieval church can’t be condemned for both scholasticism, which was Aristotelian, and for believing in a flat earth, because the two are mutually exclusive.
By the way, it’s a rather quick and easy read. I recommend it.