According to Aristotle, hylomorphism is, roughly, the view that (some) things are composites of matter and form, where the form is immanent in the matter. The goal of this excellent volume is to trace the history of hylomorphism from Aristotle all the way to Descartes. In addition to a helpful introduction by Charles, where he outlines the main interpretative choice points concerning Aristotle’s hylomorphism, the book consists of sixteen essays by different contributors that cover Hellenistic philosophy, Galen, Alexander of Aphrodisias, Neoplatonism, classical Arabic philosophy, scholastic Latin philosophy and finally Descartes. One might consider it a drawback of the collaborative nature of the volume that, despite some thematic steering from the editor, most articles do not pursue a single red thread, which can make it hard for the reader to put them in conversation with each other. But this drawback is heavily outweighed by an advantage of the division of labour, namely that the philosophers are not forced into one mould. After all, we are dealing with around 2,000 years of philosophy, and it is only to be expected that the interest in the hylomorphic picture shifts across the centuries and traditions. All in all, the volume makes for a fascinating read for anyone with a historical interest in the periods discussed or with a systematic interest in hylomorphism as a philosophical theory. Its main lesson, I think, is that hylomorphism is an even richer and more varied type of view than one might have expected.

In Aristotle and beyond, hylomorphism is often illustrated with artefacts, such as the bronze sphere composed of bronze (matter) and spherical shape (form). But the more important and ambitious application of hylomorphism is to organisms as composites of body (matter) and soul (form). The present volume focuses on the latter application and hence on the relation between body and soul. This is partly due to the historical fact that, at least from late antiquity onwards, psychology became a focal point of metaphysical thought and partly because of the editor’s special interest in the emergence of the Cartesian mind-body problem, which, as he has argued elsewhere, he does not take to arise for Aristotle (see, e.g., D. Charles, The Undivided Self [2021]). Broadly, then, two sorts of position are discussed in the volume. According to the first, Aristotle’s hylomorphic analysis of organisms, especially the treatment of soul as form, should be rejected. This is, for example, the view taken by the Epicureans and Stoics. According to the second position, by contrast, the hylomorphic analysis is generally right. This is Alexander’s view and that of later Aristotelians, such as Aquinas. However, as emerges from these essays, apparently anti-hylomorphist thinkers may turn out to embrace a view that resembles hylomorphism, whereas some of those who appear to be straightforward hylomorphists alter the view to such an extent that it becomes barely recognisable.

Let us begin with the apparent anti-hylomorphists. A. Bown, for example, argues that, although, on a ‘material mode’ of analysis, the Epicureans analyse things, including souls, in terms of atoms, their ‘property-based mode’ of analysis allows them to mimic Aristotle’s formal-causal explanations (p. 57). Similarly, B. Inwood suggests that the Stoic analysis of objects into pneuma (‘breath’) and matter mirrors Aristotle’s hylomorphic analysis, despite the fact that pneuma is also material. R. Helle defends a further analogy in that pneuma with its tensile motion, as it blends with (other) matter, explains why the composite is what it is, just as Aristotle thinks the form does. C. Rapp strikes a more cautious note, but argues that in one respect there is a significant similarity, namely regarding the explanation of how the soul allows the body to perform its functions. For Chrysippus develops a cardiocentric model similar to Aristotle’s, in which the soul, or (for Chrysippus) its leading part, is situated in the heart. At the other end of the timeline, L. Alanen argues against a hylomorphic construal of the soul–body relation in Descartes, but shows some sympathy for a hylomorphic reading of his account of the passions. Similarly, although R. Chiaradonna is sceptical of making too much of Plotinus’ Aristotelian-sounding account of the soul-trace in the body, he admits that Plotinus takes certain soul features to be in the body. P. Remes goes a step further and argues that for Plotinus (and Olympiodorus) phenomena like perception are essentially embodied. Similarly, M. Tuominen proposes that Philoponus’ account of perception is hylomorphist and that even Pseudo-Simplicius is not committed to Cartesian dualism. What these discussions of wildly different views – and views distant from Aristotle’s – show is that even in unexpected cases, it may be fruitful to read them in hylomorphic terms.

The reverse, however, seems true of some apparently card-carrying Aristotelians. As D. Perler shows, for instance, the late scholastic philosopher Francisco Suárez took the matter and form of a composite to be separately identifiable things for which it is metaphysically possible to exist independently of each other. The second of these claims is anathema to Aristotle since he takes the matter and form of an entity to depend existentially on each other, whereas the attribution of the first claim to Aristotle is at least very controversial. The case of Averroes (Ibn Rushd) is even more striking. S.R. Ogden argues that Averroes develops a ‘liberal hylomorphism’ that allows existentially separable substances to constitute a matter–form composite, namely human beings as matter and the material and the active intellect as form (where both intellects are existentially separate from humans, according to Averroes). Even if there is some basis for this view in Aristotle’s account of perception, as Ogden argues, liberal hylomorphism is a far cry from Aristotle’s hylomorphism, where forms are immanent in matter. A similar divergence from Aristotle can be seen in Avicenna (Ibn Sīnā), as presented by P. Adamson; in that version the sustaining cause of an organism is not its form but rather the external and existentially independent active intellect. But there are more subtle differences, too. For instance, as discussed by C. Shields, Aristotle’s claim that the form is a tode ti (‘this something’) develops a life of its own in Aquinas’ account of the soul as both a form and a hoc aliquid and thus as a particular that is ‘enmeshed’ in the composite (p. 345). Even Alexander may significantly depart from Aristotle if Alexander takes the soul to supervene on the body as V. Caston (and in a different way R. Sorabji) argues, although whether this would constitute a departure depends on one’s reading of Aristotle.

This last point indicates a difficulty I had in reading the volume, namely that the contributors have different views as to what Aristotle’s hylomorphism is. To some extent, this is inevitable because the interpretation of Aristotle’s hylomorphism is subject to controversy. Still, a shared minimal concept of Aristotle’s hylomorphism might have helped readers to orient themselves. For instance, several contributors assume that Aristotle embraces ‘strong hylomorphism’, according to which the matter of a composite depends essentially on the form of the composite, and vice versa. The assumption may not be an accident since Charles has defended this interpretation at length. But as Charles explains in the introduction, the interpretation is controversial. For there are two other views of Aristotle’s hylomorphism that, at least until recently, have been more mainstream: that he accepts ‘moderate hylomorphism’, namely the view that the matter and form of a composite are definitionally independent of each other (a reading defended elsewhere by Caston) or that he embraces what we might call ‘medium-strength hylomorphism’, namely the view that the matter of a composite depends definitionally on its form but not vice versa. Naturally, the verdict on whether some theory is ‘hylomorphist’ in Aristotle’s sense will vary depending on which of these types of hylomorphism one ascribes to Aristotle. For example, if Alexander is a strong hylomorphist, as F.A.J. de Haas seems tempted to conclude, this position could mark either a faithful adherence to Aristotle or a significant departure from him. Admittedly, if one began to write the history of hylomorphism only after one has settled these issues about Aristotle, one would never begin. But at certain junctures a more neutral framing of Aristotle’s hylomorphism would have been helpful.

A further worry is whether the hylomorphist net is not cast too widely. As both Chiaradonna in the discussion of Plotinus and P. Marechal in the treatment of Galen emphasise, the mere talk of matter and form does not yet imply that a theory is in fact hylomorphist – unless one is willing to classify even anti-Aristotelian accounts as hylomorphist, as long as they make some use of the matter–form distinction or even a distinction analogous to it. On the other hand, one could also argue that hylomorphism, even Aristotle’s hylomorphism, is often construed too narrowly. This is brought out nicely by Rapp, who argues that not only the general analysis of organisms as composites of body and soul but also the specifics of how the soul relates to the body (namely, as a principle residing in the heart) should be considered part of Aristotle’s hylomorphism – which, as we saw, opens the door for bringing Chrysippus into the hylomorphist conversation. By prompting these kinds of considerations, the volume promises further progress not only on how we understand hylomorphism after Aristotle but also how we understand his own hylomorphism. Or put differently, tracing hylomorphism from Aristotle to Descartes may illuminate not only the concerns of the historically posterior thinkers but also those of Aristotle, who did so much to develop the hylomorphic framework.

Perhaps one reason why hylomorphism has proven popular at various times in the history of philosophy (including the present time) is that it is a capacious theory: once the distinction of matter and form is on the table, with a little ingenuity, it can be applied to virtually anything. But this raises an objection of vacuity. If virtually anything can be subjected to a hylomorphic analysis of some sort, it is not clear what the distinction between matter and form even amounts to. One of the great benefits of this volume is that it stimulates further thought not only on historical issues pertaining to hylomorphism but also on the systematic questions as to what hylomorphism is and what work it can do. For by exhibiting the range of tasks that have been assigned to hylomorphism, it invites much-needed reflection on the power and limitations of hylomorphism. Overall, then, The History of Hylomorphism is a philosophically rewarding and thoroughly enjoyable book.