This little gem of a volume would be worth consulting by anyone interested in the reception of Galen in Late Antiquity, Islamic civilisation and medieval Jewish intellectual culture. It presents editions and translations of two different versions of the late-antique Summary of Galen's treatise on medical prognosis via periodic days and lunar cycles, the On Critical Days (De diebus decretoriis). The first, allegedly a translation by Ḥunayn ibn Isḥāq (d. 873) from a Greek or Syriac original, is presented via two Arabic versions that differ significantly in a number of passages, and use different technical vocabulary. The other is a fourteenth-century Hebrew translation by Shimson ben Shlomo from a lost Arabic original.

This Summary is one of the Alexandrian Summaries (Jawāmiʿ al-Iskandarāniyīn; Summaria Alexandrinorum) that played a role in the transmission of Greek medical knowledge into Arabic. These were paraphrases or compendia of the sixteen main books of Galen that, according to a report by the tenth-century Egyptian physician, ʿAlī ibn Riḍwān, were studied as part of the late-antique Alexandrian medical curriculum, of which the Critical Days was one. Scholars have generally assumed that they were Arabic translations of texts originally in Greek, but no Greek originals have been found. The study of these texts is useful because it sheds greater light on the reception of Greek medicine into Arabic.

The introduction presents a brief but informative survey of recent scholarship on the Summaries as a genre, although the editors are more interested in their contents and their approaches to Galen rather than in their chronologies or specific authorship. The editors suggest that the Summaries had two main objectives: (1) to render Galen's fundamental medical books more accessible to students in particular, and (2) to update Galen, i.e. to critique and change what the author of the Summary thought needed to be adjusted. The latter is the editors' principal contribution. Their main point is that the Summaries are often not simple paraphrases of their original. Rather, they argue that Galen's ideas in the Summaries were transmitted into Arabic, not by a simple linguistic translation, but by medical authors who took it upon themselves to modify and adjust certain of Galen's doctrines, if they were found deficient or needed to be updated according to advances in medicine or other fields. Although there has been significant reworking of Galen's ideas in the Arabic versions, the Hebrew version shows the most radical adjustments to Galen's treatise. Indeed, the editors argue that parts of the Hebrew version present new material in order to strengthen some of Galen's arguments.

The Arabic versions appear first, represented by MSS Princeton, Garrett 1 G (formerly: Garrett 1075), and Tehran, Majlis 6037 (or is it 6937? Both numbers are given). The Hebrew version, which is a critical edition based on five manuscripts, follows. Each version is provided with its own English translation. The layout of multiple versions and translations of the same text, as here, presents technical difficulties. The editors decided to publish the two Arabic versions synoptically, ‘in parallel columns' (p. 29). Unfortunately, this is not what happened. Instead, each version appears in a separate section, serially, with MS Princeton first, and both are followed by a single English translation, which is based mainly on MS Princeton, and textual differences with MS Tehran are noted in the footnotes as they occur. This minor problem is mostly compensated for by the section numbers that greatly facilitate referencing across these two versions, and with the Hebrew version.

The editors follow my edition of the On Critical Days, citing it frequently in the notes: G.M. Cooper, Galen, De diebus decretoriis, from Greek into Arabic: a Critical Edition, with Translation and Commentary, and Historical Introduction of Ḥunayn ibn Isḥāq, Kitāb ʾayyām al-buḥrān (2011). Overall, this appears to have been done accurately, although my name is misspelled in two different ways. There is not much in the way of commentary, since the editors' purpose seems to have been to get the text into print and accessible for study. Nevertheless, they have provided many helpful notes that address issues of content, concepts and textual readings.

There are minor infelicities. For example, at the beginning of the Summary, a six-fold classification scheme for crises is described, and the editors state that this scheme is original to the present text (pp. 13 and 65 n. 1) which, if correct, would support their argument that this author added things to make Galen's text more easily understood. It is true that this classification scheme is not present in Galen's original Critical Days treatise, which the editors follow closely in their edition and copious annotations. It is, however, present in Galen's companion treatise, the On Crises (De crisibus, Book 3, K 9.640–641; B. Alexanderson, Galenos Peri Kriseon: Überlieferung und Text [1967]). This omission is puzzling, since I distributed this passage from my Arabic edition of the On Crises (in preparation) in a handout when I delivered a paper on the history of Galen's crisis theory in Arabic medical authors at which one of the editors was present. On that occasion, I also quoted the twelfth-century ʿAbd al-ʿAzīz as-Sulamī who, in his Imtiḥān al-alibbāʾ li-kāffat al-aṭibbāʾ (‘The Experts' Examination of All Physicians’), attributes the scheme to Galen's On Crises. (See G. Leiser and N. al-Khaledy [edd.] Questions and Answers for Physicians [2004], pp. 48–9.)

This kind of error does not detract from the important contribution of the editions presented in this volume. It does, however, underscore the urgent need for Arabic editions of other related Galenic texts, such as the Crises and its Summary (Sezgin, Geschichte des arabischen Schrifttums, vol. 3, p. 149), and to investigate the possible connections of individual summaries, not only with other Greek medical texts, but also with other Arabic medical texts from the early period. Comparing such passages of the Summary with other parallels in early Arabic medical texts might provide more insight into the specific chronology and sources of this text. The editors are to be thanked for publishing this useful, well-arranged and attractive little volume.