Ptolemy considered the science of the stars to be of two parts. He explains this at the beginning of the Tetrabiblos, referring to them as two ways of predicting future events. The first is that by which we can know in advance the movements of the sun, moon and the stars, in relation to each other and in relation to the earth; the second is that by which we can know the changes that these movements bring about in the things that they surround: in a geocentric universe these are the earth and its atmosphere. The first science is sufficient in itself, and relies on mathematical demonstrations, which are the most dependable kinds of knowledge and for which Ptolemy refers his readers to the Almagest. The second cannot be known unless one already knows the first, and is that to which he will devote the book that follows. The book itself takes its title--Apotelesmatika--from the fact that it accounts for the things brought about (apotelesmena) by the heavenly bodies. The knowledge obtained from this second science is not as certain as that of the first, since its subject matter is individual material objects in the world surrounding us, which do not have the same stability as the heavenly bodies. The pursuit of this science should not, however, be rejected because of this. It is still possible, if one approaches the science in a way that is in accordance with philosophy (harmozonta philosophiai tropon), to learn from it.
The benefits of astrology are many. First, we feel good if we have a complete view of things human and divine (both of the past and the future): astrology is good for the soul. Ptolemy emphasises that astrology does not in itself enable one to become rich and famous. Nor do the heavens ordain an inevitable course of events, as if they had been ordained by a god. The important thing is to know what is likely to happen in the future, so that the appropriate mitigating remedies could be prepared in advance, and so that one can receive everything that arises with peace and tranquillity of mind.
In the Middle Ages the Tetrabiblos was known chiefly through the Latin translation of Plato of Tivoli, made in 1138, in Barcelona (not in Toledo, as is stated on page 1 of the book under review). Over a century later Egidius de Thebaldis (Egidio de' Tebaldi of Parma) translated the Castilian version of the lemmata contained within 'Ali Ibn Ridwan's commentary on the Tetrabiblos. We shall have to wait for the results of the Ptolemaeus Arabus et Latinus, a project sponsored by the Bayerische Akademie, who are editing both Plato of Tivoli's translation and the commentary of Egidius, to form a final judgement of the quality of these two translations. Translations from the Greek were made in the sixteenth century by Joachim Camerarius (1535), completed by Antonius Gogava in 1548, and by Camerarius's friend Philipp Melanchthon in 1553. An edition of the Camerarius-Gogova translation, again, is being prepared by the Ptolemaeus Arabus et Latinus team.
The only known translation of the Tetrabiblos from Greek in the Middle Ages is that of William of Moerbeke (d. 1286). We know that he had an interest both in Ptolemy and in celestial matters, since he translated Ptolemy's Peri Analemmatos, and Aristotle's works on the heavens and on meteorology, together with Simplicius's extensive commentary on the former. The only complete manuscript of William of Moerbeke's translation of the Tetrabiblos--Oxford, Bodleian Library, MS Digby 179--also contains 'Ali ibn Ridwan's work, with Simon Bredon's copy of Plato's translation in the margin. A second manuscript--Venice, Biblioteca Marciana, lat. XIV, 242--contains only the first book and the first nine chapters of the second. While Axel Bjørnbo and Charles Haskins were the first to discover this Greek-Latin translation in this manuscript, Fernand Bossier and Luc Anthonis were the first to recognize that the translation was by William of Moerbeke. Their arguments on the basis of its quotation by Henri Bate, can now be supplemented by Vuillemin-Diem and Steel's arguments from its quotation by Thomas Aquinas (thus, incidentally, adding another witness to the close relationship between Aquinas and Moerbeke). One can add to these documentary indications, the stylistic mannerisms of the work, which are distinctly Moerbekian. William of Moerbeke did not use Plato of Tivoli's translation at all, perhaps out of a deliberate avoidance of contaminating his work with anything taken from the Arabic.
Bate met Moerbeke at the Council of Lyon in 1274 and promised to explain to him how to make an astrolabe, which he did (the text survives). William appears to have wished to reciprocate by writing a translation of Ptolemy Tetrabiblos for Bate, who liked to compare different translations--especially those from Arabic against those from Greek--to get to the correct meaning of the original. The only other witness found so far is the Renaissance philosopher, Agostino Nifo (1469/70-1538) who made his own translation for his commentary on the first book of the Tetrabiblos: Ad Sylvium Pandonium Boviani episcopum Eutichi Augustini Niphi philothei Suessani ad apotelesmata Ptolemaei eruditiones (Naples, 1513). Nifo clearly depended greatly on Moerbeke's translation. His translation should rather be described as a revision of Moerbeke's translation by recourse to another Greek manuscript.
One importance of Moerbeke's translation is that it predates all the extant manuscripts of the Greek Tetrabiblos. Moerbeke's "translation method makes it possible to retrieve, for an essential part, the text of the Greek manuscript he used" (58), and we find it to be a manuscript with a very good text, closely related to the "best" family, and better than any other member of that family. Unfortunately, it was not used by the recent editor of the Apotelesmatika, Wolfgang Hübner, who would have been able to restore several good readings from this manuscript. As it happens, several conjectures by Hübner (and before him, by the editors Boll and Robbins) have been confirmed by the reading of Moerbeke. Above all we have confirmation of a conclusion which Hübner in fact did not adopt.
One indication that Moerbeke retains Ptolemy's original conclusion is that this version of the conclusion contains several phrases and conceits that can be found elsewhere in Ptolemy's work: e.g. that he wishes to follow a method that harmozonta tais physikais pragmateiais (303: congruentem naturalibus negotiis), a phrase similar to the one we met in the first chapter. The most striking of these phrases is tei tou mathematikou…eustokhia (303): "the good conjecture of the mathematician." This might seem a contradiction. Mathematicians shouldn't make conjectures; their conclusions are sure. But what we have here is an epitome of the argument at the beginning of the Tetrabiblos, where Ptolemy explains that he who practises astrology needs first to be a mathematician (astronomer), but then operates by means of natural science and good conjecture (like the archer who hits the target). Unfortunately, Moerbeke slightly obscures the meaning here. Usually he translates eustokhia and its cognates by bene coniectura- ("hitting well"). Here he translates the eu element as facilis--"an easy conjecture." But guessing the right answer is certainly not easy!
Vuillemin-Diem and Steel (with the help of Pieter De Leemans) have provided all that can be required in a good edition: a justification of Moerbeke's authorship, a detailed account of the relationship of Moerbeke's reconstructed Greek manuscript with the extant Greek copies, suggested emendations of the Greek text on the basis of Moerbeke's Latin, editorial principles, and finally the edition itself. The edition is provided with two apparatuses: the first comparing the Latin with the Greek, the second giving the Latin variants, and the editors' emendations. The edition is followed by a complete Greek-Latin index and a reverse Latin-Greek index. The editors are to be congratulated for providing an excellent edition of a difficult text.