The dissertation explores the conceptual structure and the epistemic foundations of the mathematical and religio-philosophical works of ʿAlā’ al-Dīn ʿAlī Qushjī (d. 1474). Current research suggests that one of Qushjī’s treatises is associated with a specific astronomical model that gave an important impulse to the Scientific Revolution in the early sixteenth century. According to recent historiography of science, it was a particular transformation that contained the critical breakthrough for the mathematical foundation of Earth’s motion. Until 2005, it was thought that Regiomontanus’ (d. 1476) Epitome of Almagest (1496) had supplied this philosophical impetus to Copernicus’ thesis on the motion of the Earth. But in 2005, it was discovered that ʿAlī Qushjī (d. 1474) [Ali Qushji/Kuşçu; علي قوشجي], mathematician, linguist and kalām scholar, had authored an earlier Arabic version of this model. This study unravels the new program of science according to the emerging constructivist project of the Kalām School, which was collated by Qushji and turned into a comprehensive theory of knowledge to serve as a new foundation for astronomy and physical mathematics more generally. This shows how in the fifteenth century, constructivist epistemology had been replacing Aristotelian realism as a foundation for a new mathematical physics. Qushjī’s elucidation on constructive semantics in his linguistic works on ʿilm al-waḍʿ as a science of Arabic language, as well as his epistemic discussions on mental existence (al-wujūd al-dhihnī) in his kalām work, Sharḥ Tajrīd al-Kalām (Elucidations on Scientific Abstraction), facilitate this undertaking. The constructive mathematical revolution brought forward by Arabic astronomy emerges as an original scientific and philosophical breakthrough against Greek realism and its geocentric worldview. It also provides the foundation for a contemporary critique of heliocentricism, which is currently also known to be scientifically untenable. The research opens the way for a better understanding of constructivist epistemology and its foundational historical association with modernity. Kant’s 'Copernican Revolution' of the late eighteenth century was itself an epistemic quest for constructivism as unearthed from the imbedded structure of the earlier revolution in astronomy. This study helps us answer new critical questions about the historical development of constructivist epistemology, its rise and continuity in time and its early conceptual transmission across cultural boundaries between the Middle East and early modern Europe.
The paper tackles the challenge faced by studying the history of science as a practice of finding evidence for a contemporary hypothesis that is conceptually and temporally removed from the localized historical context. This challenge is especially apparent in research on the Scientific Revolution, whereby the continuity between the old and the new was broken with the rapid introduction of new conceptual and epistemic frames that the historian, commonly being a non-philosopher, does not incorporate into his or her scheme. This common approach in the History of Science impedes the unbiased understanding of the historical sciences within their own cultural context. The works of the fifteenth century astronomer `Ali Qushji, whose astronomy has been associated with the Copernican Revolution, epitomizes this historical dilemma, as his astronomical/philosophical works indicate the development of a new constructivist epistemology that challenges the old epistemology of Aristotelian realism. If the historian is, therefore, not conceptually studying Qushjian astronomy as a constructivist paradigm shift, then he or she might not understand Qushji's solution to the methodological problems that he identifies with Ptolemaic cosmology. Planetary prognosis, contrary to the judgment of a "realist" historian who applies contemporary epistemic frames to the historical sciences, would not be the measure of success between a Ptolemaic model, a Tusian/Copernican model and a Qushjian one - with all three exhibiting almost identical predictive planetary positions. Alternatively, by using a constructivist methodology one is able to learn that, with his model to resolve the Ptolemaic equant problem, Qushji resorts to a constructivist mathematical tool that opens ways for the discovery of Earth's motion. As historians of science, we thus cannot understand the origins of the Scientific Revolution, which was a break with the old philosophy of the Greeks and a birth of a new worldview, without understanding first what the historical epistemic quest of this new worldview was.
The paper focusses on the relationship between the theology of divine voluntarism, the place of the Prophetic miracle, and the conception of modal contingency and the habits of nature as developed within the theological school of Kalām. This is contrasted to the Greek necessitarian philosophy of nature and its implications upon a theology of determinism. Historically, while evidence points to the fact that the first conception promoted observational experimentation and a philosophy of science founded upon an empirical a priori, the latter seems to have been responsible for keeping science within the boundaries of a hypothetical presupposition that is more akin to Aristotelian natural philosophy. In this paper, we primarily focus on the flowering of the theology of Kalām in fifteenth century Samarqand by tracing the full development of constructivism, as an alternative epistemology to Greek realism. To do that we primarily focus on Ali Qushji’s Sharh Tajrid al-Kalām. Qushji one of the greatest theologians and mathematicians, has been recently discovered in Western academia in connection to Copernicus and the scientific revolution in astronomy.
Qushji, who headed the Samarkand Observatory and was later associated with the scientific community of Constantinople under the Ottomans, wrote his magnum opus, which covers the philosophy of astronomy, as a commentary on Tusi’s Tajrid al-Kalam (Abstraction of Kalam). Qushji’s “moving eccentric” model for Mercury and Venus contained the critical philosophical breakthrough to a mathematical foundation for Earth’s motion. It was specifically this model that F. Jamil Ragep (2005) demonstrated an exact resemblance for with a diagram that appeared in Book XII (Proposition 2) of Regiomontanus’ Epitome of the Almagest (1496). Owen Gingerich (2008), Michael Shank (2008), and others have asserted the same transmission account. Earlier, Swerdlow (1973) remarked that Copernicus relied in both his Commentariolus and his De Revolutionibus upon this eccentric model of the second anomaly for the inferior planets as they appeared in the Epitome. Given the similarity in mathematical proof between that of the inferior planets (which Ptolemy rejected) and that of the superior ones (which he accepted), the breakthrough, therefore, is not one of mathematical proficiency: rather, it is a conceptual one. Ptolemy had disallowed the eccentric equivalence for the inferior planets, because the planets are never in opposition to the Sun, which means that to move the eccentric, the movement would be attributed to the Earth rather than the planet, which of course Ptolemy refused. But Qushji allowed for the possibility of Earth’s motion, as we see in his commentary on the Tajrid; thus, he is the only known pre-Copernican astronomer to have explicated and justified this model. To the contrary, Copernicus used this model to claim his heliocentric theory as a mathematical corollary, which in effect introduces a necessitarian worldview upon a constructive model that was first produced by Qushji based on the contingency of the natural world. By adopting a heliocentric view, Copernicus was applying Aristotelian syllogism to a transmitted foundation of astronomy, and, consequently, resorted to reversing Aristotle’s “stationary Earth” claim to a “stationary Sun.” Qushji never advocated heliocentricism, since constructivism as a theory of necessary knowledge does not lead to it. In fact, both geocentricism and heliocentricism are scientifically untenable, in a strict sense. With constructivism, mental existence allows for universal concepts in the mind, such as constructive mathematical models, to act as an aid to the process of individuation and astronomical perception. Qushji, who made significant progress in constructive semantics (`ilm al-wad`), brought over his general method of constructivism and in particular his individuation theory from his treatises on constructive semantics into kalam’s various philosophical investigations on subjective conceptualism and its diverse empirical applications; extending with that the constructivist theory of knowledge from linguistic usage to mathematical modelling as a bearer of a constructivist philosophy that is diffusive across cultural boundaries, which we later unsurprisingly see resemblance for with Kant’s own Copernican Revolution and beyond.