Heavenly Bodies and Their Accidents

As we continue our weekly readings of Sulayman al-Mahri’s Mir’at al-salak (Mirror of Travellers; see our previous post), wondering about the relation between cosmography and geography and navigation, as in one of the recent RUTTER Blog posts, we have come across an interesting live example of “saving the phenomena”, straight from the 16th-century Arabian Peninsula.

The context is Ptolemaic through-and-through, with al-Mahrī explaining in Chapter 5 what relates to the “accidents” of the planets in their courses. He takes a while to describe the mechanics of planetary movement, dwelling on the details of retrogradation which were so fundamental to the whole Ptolemaic edifice. So we need to brush up conscientiously on our pre-modern astronomy terms in Arabic, the epicycles, deferents, with their apogees and perigees, to follow carefully the exposition. But then, after a thorough explanation, we come across the following,

Now, it is obvious that the heavenly bodies bring to completion the circular movement inside their orb without experiencing any alteration that touches on the orb. For their movement is neither faster nor slower, nor do they go backwards on their path, or halt their movement in the actual fact itself (nafs al-amr). But all this has to do with the relation between our vision (hasab ru’yatinā) and the composition of the movements (tarkīb al-harakāt).

While it has become commonplace to cite Aristotle on the matter of “saving the phenomena”, it is well known that from the earliest times of Greek philosophy there was a tension between the perfect motion of the spheres—cf. Timaeus, “time is the moving image of eternity”—and the perceived irregularity of the astronomical phenomena. Most notable and seminal are the Platonic passages in Timaeus, Epinomis and the Laws, but for example, and more directly astronomical, here is Geminus of Rhodes (1st century BC),

The Pythagoreans, who were the first to apply themselves to investigations of this kind, assumed the movements of the Sun, the Moon and the five planets to be circular and uniform. They would not admit, with reference to things divine and eternal, any disorder such as would make them move at one time more swiftly, at one time more slowly, and at another time stand still.

Ptolemy (Almagest III, 1 and XIII, 2) is very clear about preserving as much as possible the simplicity of the models (Gr. hypotheseis), and the Middle Ages saw countless back and forth arguments on this matter, which might be said to be a conversation, at times heated!, between cosmology and cosmography, what we know to be de iure, and what we perceive to be de facto. It is all a series of disputationes maybe, lively and truly philosophical. How remarkable, then, that an unassuming Yemeni pilot of the 16th century, man of praxis and adventure, should join the conversation, echoing in his clear, matter-of-fact discourse, the arguments of so many centuries before him—from Pythagoras to al-Mahrī, just a blink of a scientific eye! [JA]

Circles and Stars Between Cosmology and Cosmography

The recently-opened Lisbon exhibition “The Emperor’s Gift: Circles of Knowledge” brings to light a recently-discovered 19th-century Arabic manuscript, a (literally) dizzying and (literally) encyclopaedic collection of circular diagrams and tables covering all the topics between heaven and earth. In fact, this Gulbenkian manuscript, called in Arabic Tuhfat al-Khaqan: Dawa’ir al-‘Ulum wa-Jadawil al-Ruqum (The Emperor’s Gift: Circles of the Sciences and Tables of the Numerals), is organized thematically in a way that reminds us of medieval encyclopaedias, notably from Ming China, following the tripartite arrangement of Heaven–Earth–Man (Tian–Di–Ren) or, roughly, cosmogony/cosmology–geography–beliefs/psychology.

The manuscript is literally dizzying because the convoluted paths of minuscule lettering force the reader to turn the head or turn the text in many ways to be able to follow: you actually have to “get your head round it”! And it is literally encyclopaedic because the great part of its contents is about transmitting a teaching (Gr. paideia) in a circular format (Gr. enkyklon): “a teaching in circles” is as literal a rendering of the Greek enkyklopaideia as we can get. This makes us think a lot about the conceptual and visual power of the circle.

Mirza Muhammad al-Akhbari, Tuhfat al-khaqan, 19th-c. MCG manuscript, fols. 2v-3r.

And in turn (how else?), from our particular RUTTER angle, thinking of navigation, orientation, windroses, and rhumb diagrams, we realise that this exhibition is at heart about one of the fundamental questions in philosophy of science: that of mathematical realism, in a Pythagorean and Galilean way, revived in our days by the mathematical universe hypothesis (MUH). The question, succinctly put, is, how can we explain that material reality be so adequately described by mathematical formulas and geometrical diagrams?

Sundial, courtyard of the Great Mosque of Kairouan.

Even only grazing this topic, needless to say, exceeds the scope of these brief lines, but let us suggest that a useful answer may be related, once again, to the Great Triad (三才 sancai) of Chinese cosmology, to a certain essential correspondence, a very familiar je ne sais quoi shared by Heaven, Earth and Man, that is, the physical order of the world beyond the earth, the order of our planet, and the properties of our mental apparatus, our consciousness. The key underlying “forms” to study, consider, and contemplate, are three: orthogonality (the grid), concentricity and radiality. This manuscript, and the extremely suggestive Gulbenkian exhibition are at once evocative, aesthetically delightful, and seriously provocative in the best philosophical way. They are welcome in every way in our times of sound bites and attention-stealing technology. [J. Acevedo]