Editing Celestial spheres (section)

====Philosophical and theological discussions====

Philosophers were less concerned with such mathematical calculations than with the nature of the celestial spheres, their relation to revealed accounts of created nature, and the causes of their motion.

Adi Setia describes the debate among Islamic scholars in the twelfth century, based on the commentary of [[Fakhr al-Din al-Razi]] about whether the celestial spheres are real, concrete physical bodies or "merely the abstract circles in the heavens traced out… by the various stars and planets." Setia points out that most of the learned, and the astronomers, said they were solid spheres "on which the stars turn… and this view is closer to the apparent sense of the Qur'anic verses regarding the celestial orbits." However, al-Razi mentions that some, such as the Islamic scholar Dahhak, considered them to be abstract. Al-Razi himself, was undecided, he said: "In truth, there is no way to ascertain the characteristics of the heavens except by authority [of divine revelation or prophetic traditions]." Setia concludes: "Thus it seems that for al-Razi (and for others before and after him), astronomical models, whatever their utility or lack thereof for ordering the heavens, are not founded on sound rational proofs, and so no intellectual commitment can be made to them insofar as description and explanation of celestial realities are concerned."<ref name=Setia>{{citation|title=Fakhr Al-Din Al-Razi on Physics and the Nature of the Physical World: A Preliminary Survey|author=Adi Setia|journal=Islam & Science|volume=2|year=2004|url=http://findarticles.com/p/articles/mi_m0QYQ/is_2_2/ai_n9532826/|access-date=2010-03-02}}</ref>

Christian and Muslim philosophers modified Ptolemy's system to include an unmoved outermost region, the [[empyrean]] heaven, which came to be identified as the dwelling place of [[God]] and all the elect.<ref>Grant, ''Planets, Stars, and Orbs,'' pp. 382–3.</ref> Medieval Christians identified the sphere of stars with the Biblical [[firmament]] and sometimes posited an invisible layer of water above the firmament, to accord with [[Book of Genesis|Genesis]].<ref>Lindberg, ''Beginnings of Western Science'', pp. 249–50.</ref> An outer sphere, inhabited by [[angels]], appeared in some accounts.<ref>Lindberg, ''Beginnings of Western Science'', p. 250.</ref>

[[Edward Grant]], a historian of science, has provided evidence that medieval scholastic philosophers generally considered the celestial spheres to be solid in the sense of three-dimensional or continuous, but most did not consider them solid in the sense of hard. The consensus was that the celestial spheres were made of some kind of continuous fluid.<ref>Grant, ''Planets, Stars, and Orbs,'' pp. 328–30.</ref>

Later in the century, the [[mutakallim]] Adud al-Din al-Iji (1281–1355) rejected the principle of uniform and circular motion, following the [[Ash'ari]] doctrine of [[atomism]], which maintained that all physical effects were caused directly by God's will rather than by natural causes.<ref name=Huff-175>{{Cite book |first=Toby |last=Huff |year=2003 |title=The Rise of Early Modern Science: Islam, China, and the West |url=https://archive.org/details/riseearlymoderns00huff |url-access=limited |publisher=[[Cambridge University Press]] |isbn=978-0-521-52994-5 |page=[https://archive.org/details/riseearlymoderns00huff/page/n195 175]}}</ref> He maintained that the celestial spheres were "imaginary things" and "more tenuous than a spider's web".<ref name=Ragep>{{Cite journal| doi = 10.1086/649338| issn = 0369-7827| last1 = Ragep| first1 = F. Jamil| last2 = Al-Qushji| year = 2001| first2 = Ali| title = Freeing Astronomy from Philosophy: An Aspect of Islamic Influence on Science| journal = Osiris| series = 2nd Series| volume = 16| issue = Science in Theistic Contexts: Cognitive Dimensions |pages = 55–57 |jstor = 301979| bibcode=2001Osir...16...49R| s2cid = 142586786| url = https://escholarship.mcgill.ca/concern/articles/m326m556v?locale=en}}</ref> His views were challenged by [[Ali ibn Mohammed al-Jurjani|al-Jurjani]] (1339–1413), who maintained that even if the celestial spheres "do not have an external reality, yet they are things that are correctly imagined and correspond to what [exists] in actuality".<ref name=Ragep />

Medieval astronomers and philosophers developed diverse theories about the causes of the celestial spheres' motions. They attempted to explain the spheres' motions in terms of the materials of which they were thought to be made, external movers such as celestial intelligences, and internal movers such as motive souls or impressed forces. Most of these models were qualitative, although a few incorporated quantitative analyses that related speed, motive force and resistance.<ref>Grant, ''Planets, Stars, and Orbs,'' p. 541.</ref> By the end of the Middle Ages, the common opinion in Europe was that celestial bodies were moved by external intelligences, identified with the [[angel]]s of [[revelation]].<ref>Grant, ''Planets, Stars, and Orbs,'' p. 527.</ref> The [[Primum Mobile|outermost moving sphere]], which moved with the daily motion affecting all subordinate spheres, was moved by an [[unmoved mover]], the [[Cosmological argument#History|Prime Mover]], who was identified with God. Each of the lower spheres was moved by a subordinate spiritual mover (a replacement for Aristotle's multiple divine movers), called an intelligence.<ref>Grant, ''Planets, Stars, and Orbs,'' pp. 526–45.</ref>