In light of his contribution to the preservation of classical philosophical works and his own production of philosophical works, George Pachymeres (1242-after 1307) has rightly been recognized as a key figure in the history of Byzantine culture and education.  Among Pachymeres' most relevant achievements the compendiary Philosophia shines as a monument to his philosophical scholarship. The Philosophia epitomizes in twelve books much of Aristotle's writings and inaugurates the late Byzantine tendency of producing proto-encyclopedic works summarizing all the available philosophical knowledge in one and the same work. Before Pachymeres, Nikephoros Blemmydes had composed epitomai only of Aristotle's logic and Physics. Earlier on, between the eleventh and twelfth centuries the 'consul of the philosophers' Theodore of Smyrna squeezed Aristotle's Physics and some of the late-antique commentaries on it into his Epitome of Nature and Natural Principles. Yet none of these earlier works compares with Pachymeres' Philosophia in its breath and its impact on later scholars. The large number of manuscripts preserving this massive work testify to its tremendous success. Furthermore, due to its completeness, the Philosophia fulfilled so well the task of providing a useful and reader-friendly summary of Aristotle's work that from then on Byzantine scholars would read and refer to the Aristotelian corpus from Pachymeres' Philosophia rather than from Aristotle's writings themselves. 
The book under review presents the critical edition of book 3 of Pachymeres' Philosophia, which is devoted to Aristotle's De caelo. The present volume follows the edition of other books of the Philosophia for the series Corpus Philosophorum Medii Aevi, Commentaria in Aristotelem Byzantina carried out by various scholars, including I. Telelis, who is also the editor responsible for the present volume. As in the previous volumes, the present edition contains a very useful introduction to the text in which the editor addresses issues such as the scope of Pachymeres' Philosophia (pp. 3*-13*: the asterisks are used to differentiate introductory material from the text of the edition), the content and method of book 3 of this work and a study of Pachymeres's modus operandi as a commentator (15*-71*), the textual tradition (73*-112*), a description of the paratextual material (113*-125*), a study of Pachymeres' language (127*-140*), and editorial principles (141*-146*). From these introductory sections we learn that while summarizing De caelo Pachymeres did not stick to the original division into four books, but organized the content of the text into three titles (sections) and chapters, probably because he thought this division of the material was more suitable for his purposes, i.e., to highlight and focus on certain parts more than others.
The Greek text has been established on the basis of the two most important witnessess to the text, namely Berlin, MS Ham. 512 (gr. 408) and MS Par.gr. 1930, the first being an autograph by Pachymeres himself, the second having been copied under his supervision. There are indeed several manuscripts preserving this work, but they all derive directly or indirectly from the aforementioned witnesses. The editor divides the critical apparatus into three sections: the first listing all quotations from Aristotelian writings, the second listing textual connections with other ancient philosophical works, the third listing corrections and alternative readings found in the two manuscripts that were collated. In this regard, it would perhaps have been better to differentiate within the second section of the apparatus between actual quotations from the commentary tradition and mere parallels with other texts. There are also a few misprints, but fortunately these are mostly found in the prolegomena and the indices.  As establishing the Greek text of Philosophia 3 is not problematic, I find Telelis' introduction and prolegomena to the edited text very useful and complete for framing the Philosophia within what has been called "the early Palaeologan Renaissance."  In what follows I shall discuss some aspects particularly worthy of mention.
In the first part of his long and erudite introduction, Telelis accepts Golitsis' view that Pachymeres' Philosophia does not only aim to provide an easy-access version of the Aristotelian corpus, but also reflects the author's attempt to defend the value of secular learning against the hostility of Patriarch Athanasios I (d. 1310).  Far from conceiving of the Philosophia as a mere instrument for improving the teaching and learning of Aristotle, Pachymeres was moved by actual concerns regarding the place and function of philosophy within Byzantine education and culture. This is relevant to a widespread and persistent prejudice, namely the belief that Byzantine intellectuals lacked invention and originality since they mostly reproduced and summarized classical material for scholarly purposes. Perhaps Pachymeres's Philosophia is not the best example to disprove this judgement. However, it might be useful to take into account that compendiary works of this kind--works that had no other aim than facilitating access to a classical or post-classical work--are not peculiar to Byzantium alone but are relatively common in the literature produced in medieval societies, including the Latin and Arabic ones. One does not necessarily have to set works such as Pachymeres' Philosophia in opposition to more philosophically creative texts, since the latter arise on the condition that a certain tradition has already been absorbed thanks to the former.
In this light, when we evaluate works like the Philosophia, it is perhaps better to drop our modern expectations for originality and to investigate the work's relevance to and impact on the readers of the time. Why did Pachymeres compose the Philosophia? What were his purposes in composing this compendium? Who benefited from it? When seen from this perspective, the Philosophia's tremendous success appears to be of great importance for reconstructing the way that classical philosophical works such as the Corpus Aristotelicum were received and transmitted--and, ultimately, how they shaped Byzantine culture and education. Telelis's long introduction answers these questions in a very complete way and is a most welcome addition to our knowledge of early Palaiologan philosophical literature.
1. On Pachymeres' life and work, see P. Golitsis, "Georges Pachymère comme didascale. Essai pour une reconstitution de sa carrière et de son enseignement philosophique," Jahrbuch der Österreichischen Byzantinistik 58 (2008): 53-68.
2. Cf. D. Harlfinger, "Aristoteles aus dritter Hand. Die Parekbolai aus der Philosophia des Georgios Pachymeres," Parekbolai 1 (2011): 171-86.
3. E.g.: p. 147* Finenze for Firenze; 147* Leibsig for Leipzig (twice in the same page); 149* Copenhague for Copenhagen; 151* and 152* Stocholm for Stockholm; 155* Varticanus for Vaticanus; 118 Cleomides for Cleomedes. In the critical apparatus all sources are cited with an indication of the editor of the text, with the exception of Simplicius' commentary on De caelo. In the critical apparatus Telelis accepts Linos Benakis' attribution to Michael Psellos of the commentary on the Physics, whereas most scholars follow Pantelis Golitsis in considering it to be the work of Pachymeres.
4. Cf. E. Fryde, The Early Palaeologan Renaissance (1261-c. 1360) (Leiden: Brill, 2000).
5. P. Golitsis, "Un livre reçu par le Patriarch Athanase Ier et retourné à l'expéditeur," Revue des études byzantines 68 (2010): 201-8.