This book is an outstanding feat of Aristotelian scholarship. It is divided into two parts. In the first part there is a general introduction by Rapp, in which the main issues and the most current solutions are presented and mapped onto the text. Rapp endeavours as much as possible to give a neutral overview of them. Then comes Primavesi's monumental edition of the text, which is accompanied by an accurate translation into English by Morison. Primavesi's text is based on a full collation of all 47 extant Greek manuscripts and takes into account Alexander's quotations of the De motu animalium (MA) and the two different models P. De Leemans postulated when editing William of Moerbeke's translation of the MA. The latter work proves to be decisive, for it prompted Primavesi to perform what he calls a ‘radical revision of the text’ (p. 71). What gives support to this claim is the assumption of new hyparchetype β, which corresponds to what M. Nussbaum referred to as the lost Majuscule MS, but which is preserved in uncontaminated form in MSS B^e (cod. Berolinensis Phillipicus 1507) and E^r (cod. Erlangensis UB A 4). Nussbaum's A and B families are rearranged under a hyparchetype α. As a result, the new text differs in 120 cases from Nussbaum's edition (1986). Both hyparchetypes α and β descend from the archetype ω, postulated as the latest common ancestor of all extant manuscripts, and ω descends from Andronicus’ edition; but as it has a set of errors shared by all MSS, it cannot be identical to Andronicus’, on the supposition that it is unlikely that some of its clear cases of corruption could already have marred Andronicus’ text. Primavesi endeavours to correct some of these errors in the hope of getting as close as possible to Andronicus’ edition (21 corrections, including the title, which goes by the board as an editorial addition of the incipit). Primavesi's method is very cautious, for he does not profess to follow β whenever its readings differ from α: his choices are ‘based on the individual merits of the readings in question, not a prejudice in favour of one of the two hyparchetypes, let alone on a general enthusiasm for hitherto unknown readings’ (p. 134). The new stemma produces a better assessment of the recurrent problems of textual criticism, and Primavesi's hyparchetype β is key to this new stemma.

Primavesi selects five cases to show that β-readings improve the transmitted text. Two of them have philosophical impact on the interpretation of the text: (i) At MA 7.701a36–b1 Bekker reads as follows: τῶν δ’ ὀρεγομένων πράττειν τὰ μὲν δι’ ἐπιθυμίαν ἢ θυμὸν τὰ δὲ δι’ ὄρεξιν ἢ βούλησιν τὰ μὲν ποιοῦσι, τὰ δὲ πράττουσιν. As ὄρεξις is divided into three species, ἐπιθυμία, θυμός and βούλησις, the disjunction δι’ ὄρεξιν ἢ βούλησιν comes as a surprise; Nussbaum excised δι’ ὄρεξιν and edited τὰ δὲ δι<ὰ> βούλησιν. Now, B^eE^rb read τὰ δὲ διὰ προαίρεσιν ἢ βούλησιν. This reading smoothes the text out and even comes with a bonus, a fuller list of the psychic causes of animal movement by the addition of προαίρεσις. However, one may wonder whether ὄρεξις in δι’ ὄρεξιν ἢ βούλησιν carries a restricted sense of desire, in contrast with τῶν δ’ ὀρεγομένων of the preceding line (in which all kinds of desire are included). On this restricted sense, only non-rational desiring is involved. The latter understanding is advocated by J.M. Cooper in a paper in this volume, and this seems to be a good reason for sticking with Bekker's text against β.

(ii) MA 6.700b17–25 is the key passage, according to Primavesi, that forces us to look beyond the α-family towards the β-family. MA 6 makes the transition from the joint-and-platform thesis to the soul as the internal principle of movement. It thus introduces the notion of that for the sake of which, τὸ οὗ ἕνεκα, and this notion immediately sets out a difference between animal motion and the movement of the universe, as the former has a limit (πέρας), the goal (τὸ τέλος), while the latter is endless. Then begins our chunk: ὁρῶμεν δὲ τὰ κινοῦντα τὸ ζῷον διάνοιαν καὶ φαντασίαν καὶ προαίρεσιν καὶ βούλησιν καὶ ἐπιθυμίαν (b17–18). These items are arranged under two headings, νοῦς and ὄρεξις (b18–23), except προαίρεσις, which is said to share in both. Now comes the incriminated passage (b23): ὥστε καὶ τὸ διανοητόν (α [E Γ1: quare et intellectuale C^aO^dSV^p]); ὥστε κινεῖ πρῶτον τὸ ὀρεκτὸν καὶ τὸ διανοητόν (β [BeErb Γ2: quare movet primum quod appetibile et quod intellectuale P]), ὥστε κινεῖ πρῶτον τὸ ὀρεκτὸν καὶ τὸ νοητόν (Primavesi). The α-reading does not seem to make much sense; consequently all modern editors retain the version that comes from P (and thus from β). It is tempting to recall Metaph. Λ 7 and its famous saying about the ὀρεκτόν and the νοητόν as that which explains how something is always moved with an unceasing motion. MA 6 makes reference to it when Aristotle says that it has already been explained how the first moved thing is eternally moved and how the first mover moves it (700b7–9). And MA 6 also refers to the De anima as soon as the soul as principle of movement is introduced (700b4–6). But it remains to explain how the soul moves the body, i.e. what is the principle of the animal self-motion (700b9–11), which requires us to explain that all animal movement has a limit, in contrast to the unceasing movement of the universe. In the De anima the ὀρεκτόν and its soul-counterpart, the ὀρεκτικόν, are the ultimate causes of movement for animals, and they involve the νοητόν, for the ὀρεκτόν cannot be the unmoved mover otherwise than by being thought or imagined (De an. 3.10.433b12). But in the MA, to follow again Cooper's lead, an elaboration is made in which thought (or whatever can play its role, like imagination) becomes the ultimate cause of animal self-motion as thought connects the soul to obtaining the object of desire. It is thought that shapes the desiring in such a way as to cause the animal to pursue the goal or to avoid it. Read in this way, one can reconstruct the argument of MA 6 as follows: (a) we all see that thought and desire move animals, but we have yet to determine which moves without been moved and which moves being moved; (b) that both move the animal can be shown this way: desire obviously moves, but so does προαίρεσις, and if προαίρεσις, so does the διανοητόν, for decision joins together the διανοητόν and the ὄρεξις. Thus (c) the διανοητόν is also a mover; more precisely, (d) the διανοητόν is a mover in so far as it is the discursive thought that is connected with what is achievable as the goal of an action (τὸ τῶν πρακτῶν τέλος, b25), and, under this description, (e) a thing of this sort (τὸ τοιοῦτον) is the mover (τὸ κινοῦν, b25–26), the unmoved mover on the basis of which we explain animal self-motion and its limitedness. So, the key element is the διανοητόν so conceived, and here occurs a reversal from the picture drawn in the De anima. For, when the MA investigates self-motion and its limitedness, the crucial thing is the internal representation of the object of desire, and this is the noetic apprehension of it. As a result, one goes on to examine in the next chapter ‘how is it that when one is thinking sometimes one acts and sometimes one doesn't’ (MA 7.701a7–8), and this is what one should expect if the MA is not only summarising the De anima but elaborates on it by setting in the spotlight the decisive role thought has if animals are to move themselves. This explains the prominent role thought (or imagination) plays from MA 6 onwards. On this scenario, the α-reading becomes less reprehensible, for its seemingly incomprehensible reading ὥστε καὶ τὸ διανοητόν <supplementing: is a mover> makes the important step (c) by which thought enters the stage. And as soon as thought enters the MA picture, it takes centre stage. On the other hand, one may be suspicious that what the β-reading is doing is trying to harmonise the MA with the De anima and the Metaphysics view. This harmonisation may be the work of a highly qualified scholar who wants to smooth things over, with the gratification of recalling a famous passage from Metaphysics Λ. Such an attempt, if an attempt it is, gets cemented by Primavesi's ὥστε κινεῖ πρῶτον τὸ ὀρεκτὸν καὶ τὸ νοητόν, where one finds that theorem of movement whose authenticity ‘is indeed supported, in substance, by a famous parallel passage from Metaph. Λ 7’ (p. 73). But if one recalls that the MA shifts the focus to self-motion and that self-motion is necessarily limited, the external object of desire loses much of its glamour, for what matters now is the internal representation of it. It is a detail, but maybe a significant one, that the word ὀρεκτόν appears only once in the MA if one adopts the β-reading of this passage. So, philosophical decisions lie again at the crossroads of different readings, one of which may arise from too much familiarity with other texts and some eagerness to make of them a seamless unified theory, while the other one looks definitely like an ugly duckling, but points to a significant elaboration of the point at issue.

In the second part of this book, the MA chapters are minutely and scholarly scrutinised. The reader cannot but be impressed by the quality of the analyses and the high standard of scholarship with which they are all carried out. Special mention should be made to what is called the Coope–Morison hypothesis, according to which MA 3–5 are directly connected to the explanation of animal self-motion as they disclose the necessity of an unmoved mover for animal self-motion by comparing it with the movement of the universe, and then MA 6–10 go on to show that this is the internal representation of the object of desire by thought, and to understand its physiological mechanisms by means of heating and chilling, expansion and contraction. P.-M. Morel also endeavours to show that MA 11 is connected with the whole enterprise as this last chapter of MA tackles the cases in which animal movement occurs despite thought's waning role, or even despite its absence, like the beating of the heart or sleep and waking. It is a pity not to be able to go through all these very illuminating essays because of lack of space, but I hope I have given a taste of how rewarding this book is for those who study Aristotle's biology and his theory of motion, and more generally how remarkably rich it is for reassessing Aristotle's way of thinking.