I.1 Aristotle’s Parts of Animals as Philosophy
One might wonder about the value of studying Aristotle’s Parts of Animals (PA) if one’s interest is chiefly philosophical. Aristotle’s detailed study of the bodies of animals initially appears to be part of the history of science, an early attempt to categorize or conceptualize divergences in animal anatomy. Thought of in this manner, one might worry about contemporary irrelevance (given the relative sophistication of modern zoology) and a disconnection from the more enduring parts of Aristotle’s thinking. These misgivings, although understandable, are unnecessary since this work is of the upmost importance for Aristotle’s philosophical program. The Parts of Animals is a core part of Aristotle’s project of uncovering and elucidating the structure of reality employing logical tools. Living beings, and especially animals, are the most complete substantial realities that human beings have access to in their environments. Through studying the parts of animals, which contribute to the living capacities of the whole entity, we learn about important ways in which the world works, from the inside out.
The Parts of Animals Book I contains one of the most powerful encomiums to the study of animal life in the Western tradition, arguing for the value of even the lowliest species due to their beauty and wonder (PA I.5). Philosophically-minded students of the natural world must logically order animals and their parts to gain knowledge, which applies not only to the work itself but more broadly to the entirety of Aristotle’s “inquiry concerning animals and plants” (Meteor. I.1, 339a8). Living beings maintain themselves in existence due to their complex organizational capacities. Furthermore, the life of animals rather than of plants is to be the primary focus because their way of being alive involves sensory responses that are a kind of knowledge; given this, they also display more order and unity. Human beings are also animals and thus finding out about how the bodies of animals function provides necessary insights about our own existence; in the case of humans, we naturally seek knowledge for its own sake, for the sheer joy of understanding (Metaph. I.1). Inquiry leads us to understand the structure of things, including ourselves, and provides materials for the ultimate aim of philosophy, to contemplate what is true.
Almost a quarter of all Aristotle’s extant works directly discuss animals; in addition to the Parts of Animals, the most significant of these are the Generation of Animals (in five books) and the Historia Animalium (in ten books).Footnote 1 In the last century, those working on Aristotle’s philosophically motivated natural science began to recognize how crucial all these works are to understanding his thought. In terms of logic, philosophy of science, epistemology, psychology, metaphysics, and ethics, the biological works contribute significantly to our picture of Aristotle’s methods and commitments.Footnote 2 This important development in scholarship on Aristotle is sometimes termed the ‘biological turn.’
A reader might, however, wonder how it can make sense to view Aristotle’s works on animals as ‘biology,’ since the term was not invented until the late eighteenth century.Footnote 3 This term need not be anachronistic if care is taken not to solely import contemporary understandings. Insofar as Aristotle undertook a systematic study of mortal living nature, and included careful empirical methodologies, there are good reasons to label his work biological. Very generally, Aristotle collects the facts (the ‘that’) before seeking causal explanations of these facts (the ‘why’) (A. Po. II.1, 94a20–36). He studied the basis of life and its manifestations in animals and, to a certain extent, plants.Footnote 4 On the other hand, unlike contemporary biology, Aristotle did not view his endeavors as separate from the study of philosophy. Many of his concerns are more general, for example, to find that the structure of reality aims toward ends; the ends in nature are generally to sustain the way of life of the kind across generations. There is no conceptualization of evolution but rather a recognition of the continuity of natural patterns, grounded in functional optimality.Footnote 5
This brief introduction will explain how the Parts of Animals came back from obscurity to be recognized as a significant part of Aristotle’s philosophical endeavors in the last century. It will then give a brief overview of the structure and content of the work. The final section will introduce the philosophical topics in relation to the text presented in each chapter of this book.
I.2 The Study of the Text
The Parts of Animals is central to Aristotle’s philosophy of science. And yet for many centuries, it was sidelined by those interested in Aristotle’s philosophy. While biologists and zoologists had long recognized Aristotle’s prominence, the separation of science from philosophy left the PA behind.Footnote 6 By the nineteenth century, developments in the biological sciences saw a resurgence of interest in the text, which eventually reached the consciousness of philosophers. Two decades before the publication of Charles Darwin’s On the Origin of Species, a famous debate raged between the French biologists George Cuvier (1760–1832) and Etienne Geoffroy Saint-Hillaire (1805–1895) over the organization of animals. For Cuvier, the emphasis had to be on the function of bodily parts and their interrelation, based on Aristotelian teleology.Footnote 7 For Geoffroy, the similarities between parts of different animals, regardless of function, was central, labeling these ‘homologues.’ A hundred years later, modern evolutionary science realized the necessity for and complementarity of both form and function.Footnote 8 Both aspects can be found in Aristotle’s work on animal parts – the focus on the integration of parts and their functions as part of the whole, as well as a keen perception of the similarities across kinds in the shapes of body parts.
This extraordinary work comes to the consciousness of contemporary scientists and classical philosophers during this period of transition. William Ogle, a naturalist and physician, translated the text with notes in 1882 and sent it to Charles Darwin.Footnote 9 His response was as follows:
I have rarely read anything which has interested me more; though I have not read as yet more than a quarter of the book proper. From quotations which I had seen I had a high notion of Aristotle’s merits, but I had not the most remote notion what a wonderful man he was. Linnaeus and Cuvier have been my two gods, though in very different ways, but they were mere schoolboys to old Aristotle.Footnote 10
Arthur Peck, a student of classicist and philosopher Francis Cornford in Cambridge, completed a translation with extensive introduction and notes in 1937.Footnote 11 The French edition by Pierre Louis followed in 1956.
The 1970s and early 1980s produced significant advances in understanding the contents of the Parts of Animals and its role in Aristotle’s philosophical program.Footnote 12 There are two key aspects to this reevaluation. First and foremost, the work provides a methodology for biological investigation. This enriches and supplements the scientific and epistemological methodology detailed in works such as the Posterior Analytics. In PA I, Aristotle presents and defends various standards that circumscribe the requirements for explanatory accounts of natural phenomena. Secondly, PA II–IV engages directly with the application of this methodology to morphology, anatomy, and physiology in animals. We find here also the natural philosopher grappling with the application of many crucial philosophical concepts in this field of inquiry including substance (ousia), species/form (eidos), matter, analogy, nature, cause, necessity, division, and definition; each are applied with sensitivity to the subject matter and in the appropriate explanatory context.
Brief Description of the Contents of the Text
The text has two main aims, method and practice. PA Book I is a guide and introduction to how to study life and provides preliminary considerations about how to investigate all aspects of animal nature. PA Books II–IV is our most comprehensive evidence of the application of Aristotle’s philosophical methodology to real world examples of substances, that is, to animals.
Book I, chapter 1 of the Parts of Animals sets out several key methodological principles in the study of living nature. Aristotle begins thus:
So it is clear that for the enquiry into nature (περὶ φύσιν ἱστορία), too, there should be certain standards (ὅροι), such that by referring to them one can appraise the manner of its proofs (ἀποδέξεται).
Whatever he means by “standards” Aristotle is clearly concerned to provide general guidelines as answers to a series of questions. The first question is one of the most important.
I mean, for example, should one take each substantial being (οὐσίαν) singly and define it independently (καθ’ αὑτήν), e.g. taking up one by one the nature of humankind, lion, ox, and any other animal as well; or should one first establish, according to something common, the attributes common to all? For many of the same attributes are present in many different kinds of animals, e.g. sleep, respiration, growth, deterioration, death, and in addition any remaining affections and dispositions such as these.
This question reflects ontological and epistemological tensions in Aristotle’s philosophy. What should we look to, the particular kind, which can no longer be divided into others, or a wider kind to which several belong? In zoology, this becomes a question of what sorts of explanations are appropriate in particular instances. In some cases, such as in explaining sleep, growth, or respiration, there are no more-or-less differences between how these occur in different animals. All animals grow, deteriorate, and die, so the account can indeed cover all instances.Footnote 13 In other cases, however, one type of affection does not cover all kinds; for example, animals locomote in very different ways. Thus, locomotion although the same in genos is different in different animals (e.g. flying versus swimming).Footnote 14 Sometimes it is appropriate to concentrate on what is entirely distinctive of a certain kind of animal in order to explain its affections, dispositions, or parts. For example, only one species of octopus lacks a double row of suckers; Aristotle explains why thus:
Now while the other octopuses have two rows of suckers, one kind of octopus has a single row. This is because of the length and thinness of their nature; for it is necessary that the narrow tentacle should have a single row of suckers. It is not, then, because it is best that they have this feature, but because it is necessary owing to the distinctive account of their substantial being (διὰ τὸν ἴδιον λόγον τῆς οὐσίας).
PA I also introduces and defines other general guidelines. The philosopher of nature, like the astronomer, should seek the facts before attempting to establish the reasons why (639b7–11) – but for the biologist, following this guideline is much more complicated than it is for the astronomer. In giving reasons, the biological thinker must reference final causes alongside necessity and must give priority to the final cause over material and efficient causes. In terms of necessity, they must be aware of its different manifestations in nature (639b12–640a9). Particularly important is conditional (or hypothetical) necessity, referring to what is required if natural processes are to achieve their ends; indeed, it is not the process but the end point that is the focus of this study.
Hence it would be best to say that, since this is what it is to be a human being, on account of this it has these things; for it cannot be without these parts.
The rest of PA I investigates other general principles in the study of animals, explaining the right and wrong ways to employ the method of division (PA I.2–3), how to use analogy and “the more and the less” (I.4), and why it is crucial for the philosopher to study living beings, despite feelings of disgust, since “in all natural things there is something marvellous (τι θαυμαστόν)” (I.5, 645a16–17). The end of PA I returns to the initial question of whether to study particular or general kinds and suggests that the study will proceed both by atomic species (ἄτομον τὸ εἶδος), the last undividable kinds, and also in broader groupings when general explanations are possible. The latter methodology avoids needless repetition (I.5, 645b13). However, the former is also required in certain cases, for example, the slimline octopus.
PA II begins with three levels of composition: elements into simple compounds, simple compounds into uniform parts of animals, and, finally, uniform parts of animals into nonuniform parts of animals. Uniform parts include, for example, flesh, bone, and blood; nonuniform parts include, for example, face, hand, and stomach. Aristotle focuses on the last two levels explaining why animals must have both types of part, why sense-organs must be uniform, and why viscera are in one way uniform and in another way nonuniform. From chapter 2, he begins the study of uniform parts, listing their texture, causes, and the differences between them. A part-by-part review begins, starting with blood, the nourishment for the whole body. The other uniform parts are arranged from more fluid to more solid. The study of nonuniform parts begins in chapter 10 with those “most necessary” to all animals, the ones that receive and expel nutriment as well as the origin of life, which lies in-between these two others (655b37). Aristotle notes an increased complexity from plants to humans and first focuses on blooded animals, treating the bloodless ones later.
Uniform parts are mostly treated from top to bottom (mapped onto the human body) – and the general pattern is to start with the most common features, those that appear in the widest class, and then to move on to differences that occur between groups of animals.Footnote 15 Animals are “grouped and regrouped” (Balme Reference Balme1987b: 88) as needed to find the widest-class generalizations for each part. Having completed viscera, Aristotle turns to bloodless animals, explaining at first why they lack viscera. Grouping them into four kinds, using cephalopods as his model, he proceeds to describe their internal parts, beginning with those used for nutrition and then detailing sense-organs. Parts of Animals IV.5, 682a30–34 marks the end of the survey of internal parts; Aristotle announces that the external parts will be detailed starting from bloodless and then to the blooded animals. The procedure begins part-by-part, first uniform then nonuniform, proceeding from the top to the bottom (based on human uprightness), and finally moving from external to internal and back again to external. Focusing on parts, Aristotle explains why a possessor has the part it does and why one possessor has the part differently configured from another possessor.Footnote 16
One interesting feature of PA II–IV is a resistance to any dogmatic attempt to draw a line between types of living being; there are cases that require the researcher to understand that nature allows for some organisms to have features usually associated with two kinds or even of two habitats. As James Lennox explains: “The entire investigation ends by looking at various blooded animals that do not fit naturally into the four extensive kinds [viviparous quadrupeds, oviparous quadrupeds (including snakes), birds and fish] recognized throughout PA II–IV” (2001a: 343). The use of epamphoterizein, meaning “tending to both sides,”Footnote 17 shows how Aristotle employs close observation and is sensitive to the actual lifestyles of animals. He even uses his knowledge of botany to help to explain how certain animals operate.
Through the mid-line of the ascidians there is a think diaphragm, in which it is reasonable for that which controls life to preside. But those that some call ‘nettles’ and others ‘anemones’ are not hard-shelled, but fall outside the divided kinds, and tend in their nature towards both plant and animal. For by being detached and falling upon their nourishment, and by being perceptive of what they fall upon, some of them are animal-like; and further, they use the roughness of their body for self-preservation. But by being incomplete and becoming quickly attached to the rocks, and by having no apparent residue though they have a mouth, they are akin to the kind consisting of plants.
Such challenges in the study of animal parts and their functions indicate to Aristotle the organizational complexity of reality. It is not a simple matter of dividing in terms of “cutting nature at its joints,” as a butcher would dismember a carcass (Plato Phaedrus 265e). The study of animals requires a much more robust logical range, revealing the intricacy of human reasoning capabilities.
Throughout PA II–IV, Aristotle focuses his explanations on ends in nature and particularly the formal nature of Book I (640b28).
Since every instrument is for the sake of something, and each of the parts of the body is for the sake of something, and what they are for the sake of is a certain action, it is apparent that the entire body too has been constituted for the sake of a certain complete action.
While scholars disagree about the exact import of this passage, it gives a clear sense of Aristotle’s emphasis on the function of body parts toward the achievement of living goals.Footnote 18 In this context, the formal natures of animals have agency in shaping them in the best manner possible. This analysis can also explain how nature leads to living well over and above mere survival.Footnote 19 Furthermore, material natures contribute to the way in which animal bodies are molded so that animals can live well in their natural setting.Footnote 20 An excellent example of this type of explanation occurs in relation to the presence of horns.
Since there is a necessary nature, we must say how the nature according to the account makes use of things present of necessity for the sake of something. First of all, what is bodily and earthen is present in greater amounts in the larger animals, while we know of no completely small horn-bearing animal – the smallest one known is a gazelle. And one should study nature with a view to the many; for it is what happens either in every case or for the most part that is in accordance with nature. What is bony in the bodies of animals is in origins earthen; this is also why it is most abundant in the largest animals, to speak with a view to what occurs for the most part. For the residual surplus of this sort of body, being present in the larger of the animals, is used by nature for protection and advantage, and the surplus, which flows of necessity to the upper region, in some cases it distributes to teeth and tusks, in others case to horns.
While there is much to connect the general philosophy of biology found in PA I with the rest of the work, there are few clear accounts of conditional necessity and no definitions of the essence of kinds, as one might expect in these latter books of the treatise. The philosophical norms of PA I are reflected in PA II–IV but sometimes these are under strain (Lennox Reference Lennox2001a: xiii). Careful treatment is required to make clear how final causes, formal agency, and definitional goals operate in Aristotle’s analysis of animals’ parts in PA II–IV.
I.3 The Philosophical Work Achieved by the Chapters in This Volume
PA I provides a program of study, focusing on formal and final causes of animals, noting that materials are for the sake of ends. Much of PA II–IV carries through with various more detailed attempts to explain animals’ parts, both those that are common to or shared across broader groups and those that are peculiar to a certain kind of animal. Different strategies are apparent in the text; sometimes there is an emphasis on what animals have in common across kinds and on comparisons that bring out these similarities; at other points, we find particular animals’ ways of life are central to explanation. Similarly, there are times when the prioritization of formal and final causes takes precedence, while at other times, the materiality of the parts is brought to the fore. The chapters in this volume take up different strands of these discussions in the text, some focusing more on broader groupings, some on particular kinds of animals; some have more to say about formal and final causes and some focus more on material ones.
The first set of chapters (1–3) concentrate on the text itself – its rationale, connections with other works in the Aristotle corpus, and its legacy. Myrto Hatzimichali (Chapter 1) considers the place of the PA within the biological corpus and the status and placement of PA I with relation to the rest of the treatise. She argues for retaining this Book within the PA, but as a theoretical introduction applicable to Aristotle’s entire explanatory project in zoology, and also makes a case for positioning the Historia Animalium before PA I. The next chapter by Monte Ransome Johnson (Chapter 2) concerns how Aristotle sought to persuade various audiences of the philosophical and human value of studying animals and their parts. In the main, despite a few exceptions, this value is due to the way that they display order and the operation of final causes. Johnson puts the so-called protreptic section of PA I.5 where these ideas are expressed into the context of rhetorical methods in the Aristotle corpus. Giouli Korobili (Chapter 3) considers how the systematic elements of Aristotle’s zoology began to be overlooked very soon after Theophrastus; part of the reason for this would appear to be the subsequent neglect of PA I. She explains how the work as a whole, and its teleological perspective, was considered carefully by Galen, even though his own rhetorical flourishes sometimes obscured its importance. In the final section, she sets out methods of analysis of the PA in the fascinating late Neoplatonic commentary by Michael of Ephesus, which has yet to be translated from Byzantine Greek.
The next four chapters (Chapters 4–7) are mainly concerned with PA I and how to understand Aristotle’s preliminary principles for the study of animals. Jessica Gelber (Chapter 4) analyzes Aristotle’s dissatisfaction with rival theories and argues that rather than presuppose a teleology that they may reject, his strategy is to undermine their explanations in other ways. According to Gelber, Aristotle prioritizes teleological over non-teleological explanations because the former are based on definitions. Definitions are appropriate starting points that prevent explanations from going on ad infinitum. Hypothetical or conditional necessity is just one kind of explanation that does provide such grounds; it is possible that there are others that might also avoid Aristotle’s critiques.
For Aristotle, the predecessors who discussed life and animals did not provide correct explanatory accounts of their existence as substances. His own strategy is to emphasize organic unity where the functioning parts are for the sake of this whole. There is controversy about how this works. Aristotle does not provide definitions of species forms; how, then, might one think about animal essences? This volume presents different ideas about how form and essence work in theory and in practice in the text. Michail Peramatzis (Chapter 5) provides an account of the relationship between form and matter in animals as inextricably intertwined. This means that definitions of essences will include “subtle” matter such as being blooded or winged. This represents an innovative position on the adaptation of hylomorphism in the biological context and how important Aristotle’s biology is to understandings his mature metaphysics. In Chapter 6, Devin Henry shows how in certain cases, at least, the subject matter of zoology is “atomic species” (atoma eidos), the end of the correct division into kinds, involving multiple differentiae. He argues that Aristotle treats atomic species as the primary objects whose essences we are attempting to grasp in zoology. Species here is meant in an Aristotelian rather than a modern sense, meaning a place where the division of kinds ends; this clarification helps to support the idea that Aristotle’s explanations of animal parts depend on which atomic species they belong to. Thomas Johansen (Chapter 7) argues a related point, which is that explanations often require specificity at the level of “ultimate species” (atoma eidos).Footnote 21 For example, one must refer to this level of reality when a part is used in a particular manner due to the material constraints of an animal’s situation. Also, the part and its function can only be understood in relation to one of the other parts of this particular species, viewing body parts as interconnected, rather than only concentrating on them in isolation. Thus, it seems that in such instances, wholes come first rather than parts, which is in keeping with the methodology recommended at the outset of the work.
Chapters 8–12 explore explanations that are comparative and focus on features shared across different kinds of animal, some of which are described as analogous. Christopher Frey (Chapter 8) wonders how analogy as discussed in Aristotle’s logical works might be applied in the field of zoological research. What, if anything, unifies analogous parts? It seems that there is, in most cases, no higher genus as a point of reference; and, at times, function is not all that is indicated by the term. Stasinos Stavrianeas (Chapter 9) provides a detailed account of how animals’ uniform parts are constructed. He explains that they develop from the concoction of materials and that this preserves the capacities that are required for the life of the animal. In doing so, he shows the crucial dependence of the discussion of uniform parts in PA II on theories espoused more fully in the chemical and physical works, especially On Generation and Corruption and the Meteorologica. Sophia Connell (Chapter 10) concentrates on one uniform part, blood, and its connection to a curious feature: animal character. Although Aristotle gives seemingly only a “material” explanation of differences in blood which underlie character dispositions, there are strong connections to formal and final causality, through the animal’s material nature. Material thermodynamics, as described by Stavrianeas, are used by the animal’s formal nature to determine a material basis for character (cf. GA II.6, 743a36–b18). However, most animals are at the mercy of the materials that sit in the blood vessels at certain times in the nutritive cycle, over which they have little control.
Mariska Leunissen’s Chapter (11) marks a transition from thinking of general to more specific cases and from uniform to nonuniform parts. Aristotle sets out to explain a wide variety of different parts in all their intricacy, even odd or anomalous anatomical features. Some of these do not appear to be for the sake of anything and may even be detrimental. Thus, in accounting for the nature of animals as like craft, he comes up against certain limitations in these cases (unaware as he was of the residual forces in evolution).
The final set of Chapters (12–14) switch between a focus on a particular kind, human being, to a comparative approach whereby other animals are compared to humans. Mary Louise Gill’s question (Chapter 12) is the most general one relating to human, whether intellect (nous) itself, as manifested in the lives of human beings, can be part of the study of nature. She argues that it is possible to read PA I.1, which appears to suggest that intellect is not part of the study of nature, as a dialectic exchange with certain Platonists who attempt to separate mind and nature. There is a way, then, to read the text that does not require us to think that Aristotle endorses a view at odds with other parts of his philosophy of nature, namely that embodied thinking is entirely supernatural. Christof Rapp (Chapter 13) sets out the peculiarities of human parts, morphology and orientation in space. He explains how Aristotle’s account of the human body in PA IV.10 works and how he uses his conclusions to understand the nature of certain other animals in comparison with human morphology. Emily Kress’s Chapter (14) similarly focuses on the relation of human to nonhuman animals and explains Aristotle’s rationale for treating human beings first and as a model for the study of the parts of other animals. According to Kress, polymorphicity, the complexity of human parts, provides the most teleologically rich model for parts in other animals. The most articulated parts can then be mapped onto simpler ones and thus the functions in the latter discerned more clearly. Together this volume offers a rich picture of the philosophical interest of the Parts of Animals and invites further reflection on and argumentative engagement with this fascinating treatise.Footnote 22
