Taken together, all the previous evidence of the interdependence between the works of Copernicus and those of 'Urḍī, Ṭūsī, and now Ibn al-Shāṭir, must at least strengthen the claim of a westward transmission of astronomical ideas from the world of Islam to Renaissance Europe. The works and newly invented theorems and mathematical techniques of 'Urḍī, Ṭūsī and Ibn al-Shāṭir, were all organically and integrally connected to the preceding results of Islamic astronomy. This evidence clearly demonstrates as well how the totality of those earlier results had by the sixteenth century become the tools of the new astronomy that Copernicus was beginning to construct. When all that evidence is taken together, then it is in that sense that one must understand the statement of Swerdlow and Neugebauer, in their latest book on the mathematical astronomy of Copernicus, when they tried to see Copernicus as the last Marāgha astronomer rather than a completely disconnected figure who was forging a new astronomy completely based on new grounds of his own construction.[326]
All the evidence just cited, and the remarkable similarities between the works of Copernicus and the works of his predecessors from the Islamic world have not gone unnoticed as we have seen. In fact it continues to raise some very fundamental questions about the actual intellectual environment in which Copernicus conceived his path-breaking work. And like all good research results, this connection between Islamic and Copernican astronomies does not only raise new questions for the students of Copernican astronomy, as it must do, but also in turn it raises some very interesting problems for Islamic astronomy as well, as we shall soon see.
Even if one grants the existence of those connections on the intellectual level, still the problem of contacts between Copernicus and his predecessors, in the historical sense, remains further complicated by the fact that we have no evidence whatsoever that Copernicus himself knew any Arabic at all. We also have no evidence that any of the works of 'Urḍī, Ṭūsī or Ibn al-Shāṭir, with which Copernicus seems to be in direct contact, had ever been translated into Latin in the same way that other Arabic sources were translated earlier into Latin. We cannot speak about the works of these astronomers in the same way we speak about the translations of the works of Avicenna or Averroes that went into Latin during the medieval period. We cannot even compare them to the translations that took place during the Renaissance, such as the fresh translations of the Avicennan works that were executed by Andreas Alpagus,[327] for there does not seem to be an equivalent Andreas for the astronomical works. And yet we know that the results that were produced in the Arabic astronomical works mentioned before, seem to have found their way to the technical repertoire of Copernicus so that he could use them so freely in his own construction of his own astronomy, and at times even use them without digesting them fully as we just saw in the case of Mercury.
Furthermore, we know that these same mathematical theorems and techniques, which must have seemed as novelties to Copernicus, were extensively used by Arabic-writing astronomers for centuries, as we just saw, well before Copernicus, as well as contemporaneously with him, and even after his time. They have a continuous tradition in the Islamic domain for which we find no parallel components in the Latin West. There is some mention of the use of the Ṭūsī Couple at the time of Copernicus in the Latin sources,[328] but that is almost the full extent of it. One does not find the multiplicity of similarities that were just discussed.
From a slightly different perspective, and for the purposes of the results that will be drawn later, we should note at this point that those same astronomical results that were established in the Islamic domain were expressly generated in the context of objecting to, reformulating, and casting doubt on the Greek astronomical tradition. In a sense, unlike the works of Avicenna and Averroes that could have been arguably translated into Latin in order to harvest the older Greek Aristotelian thought that they contained, those mathematical and astronomical results represented their own rebellion against those Greek sources. From them one could not recover Greek thought. On the contrary, one rather found the very critique of Greek thought. In themselves, those Arabic astronomical sources were creating alternatives to Greek astronomy instead of "preserving" it as we are often told. And most surprisingly, they all came from the period that has been dubbed, for centuries now, as the period of the deepest decline in Arabic thought.
So why a Renaissance scientist would be interested in recovering information from such sources, when these sources were representatives of a declining culture, if we were to believe the classical narrative of Arabic scientific historiography? Furthermore these sources were written expressly to counter Greek astronomical thought rather than preserve it. So why any Renaissance scientist would be interested in them, if the purpose of the Renaissance intellectual project was the recovery of the sources of classical Greco-Roman antiquity as we are also so often told?
On the other hand, when we remember the iconographic treatment to which Copernicus has been subjected, by those who name revolutions after him, and the portrayal of his revolutionary role as a path breaker, it will become difficult to imagine how and why would the same person seek results from sources that were steeped in saving Aristotelian cosmology, such as the Arabic astronomical sources seem to have been doing. If his purpose was to topple that cosmology altogether, as we are told by the literature about Copernicus, wouldn't he have looked somewhere else? Furthermore, if we are to believe that the works of Copernicus crystallized the spirit of modern Renaissance science, then we would have to contend that the basic technical foundations for this "modern" science were already laid in the Islamic world, centuries before, as we now realize that the only two theorems that were used by Copernicus to construct his own astronomy, that were not already found in Euclid or Ptolemy, were the theorems of 'Urḍī and Ṭūsī. All these questions and reflections force us to review our standard historiography of Renaissance science first, and then, most importantly, the historiography of Islamic science itself.
Among the problems that the project of Islamic historiography must entail is that of explaining which Arabic work may have been available to Copernicus, if we were to continue to think that those astronomical results reached Copernicus directly from Arabic sources. The difficulty becomes critical when we realize that so far we can establish similarities between the works of Copernicus and the works of 'Urḍī, Ṭūsī and Ibn al-Shāṭir, but in such a way that none of those Arabic sources could account for all those similarities. That is, if we were to assume that Copernicus knew of 'Urḍī's work, we cannot explain from that work alone his knowledge of Ṭūsī's Couple. And if we assume he knew of Ṭūsī's work, then we cannot explain his acquaintance with 'Urḍī's work through Ṭūsī's work. And if we assume that he knew of Ibn al-Shāṭir's work, who lived a century after 'Urḍī and Ṭūsī, then we cannot explain Copernicus's insistence on proving the Ṭūsī Couple which is nowhere proved in the work of Ibn al-Shāṭir. And of course it becomes almost impossible to conclude that he knew of all these works individually and that he synthesized them himself when he did not know any Arabic, nor having had any of them available to him in Latin.
326
Noel Swerdlow, and Otto Neugebauer,
327
See Marie-Thérèse d'Alverny,
328
For the use of the Ṭūsī Couple by Giovanni Batista Amico in 1536, see Noel Swerdlow, "Aristotelian Planetary Theory in the Renaissance: Giovanni Batista Amico's Homocentric Spheres",