Aristotle considered animal generation to be such a complex and important part of his philosophical biology that it required a separate theoretical study all of its own. The treatise entitled Peri Zôiôn Geneseôs (On the Generation of Animals (GA)) covers generation in all animals (from the lowliest up to the human being), providing a new theory of generation pitched against rival views. It explains the general development of the embryo as well as the various ways that generation is brought about in different types of animal, including egg laying in birds and fish, and larvae production in insects. The work includes discussions of anomalies, such as hybrids, monstrosities, and uterine tumors. It combines a broad cosmological view (i.e. generation is part of a series of measured patterns in nature; GA 4.10) with a focused analysis of the most particular cases that can be explained, for instance, why animals breed more than one at a time (GA 4.4–5), why some mules are fertile (GA 2.8), and what causes the various eye and hair colors found in human beings (GA 5.1–4). While there are differing opinions about the structure of the treatise, it is generally agreed that the work is carefully organized, theoretically united, and comprehensive in its aims.1
The work makes clear its connections to Aristotle’s broader philosophy of nature at the outset by reiterating the four causes and providing a familiar analysis of the body in terms of instrumental parts (GA 1.1.715a3–11). This introduction signals continuity with the discussion in On the Parts of Animals; the parts that remain to be explained are those that serve generative functions. Aristotle also indicates that the efficient cause will become more prominent in his account of generation (715a11–13). This focus arguably fits with his desire, expressed elsewhere, to separate an account of “being” from that of “coming to be” in animals (PA 1.1.640a10–640b4).2 Another key methodological precept is the presentation of more specific principles (archai) required to analyze reproduction, namely the male and female principles (GA 1.2).
Aristotle avoids discussion of the generative parts (uterus, breasts, penis, testes, etc.) in other explanatory works on animals, unless the subject matter requires it.3 This is, in part, due to the desire to keep the topic of generation separate, but also has to do with the nature of sex difference. In many of his biological works, Aristotle concentrates on the fundamentality of kinds (or forms), focusing on differences between different types of animal, and similarities within the kind, that is, the atomic species.4 Sex difference, in contrast, represents a difference within the kind. As Aristotle explains, “on the one hand, in all animals that travel around, female is separated from male, and female is one animal and male another; on the other hand, they are the same in kind (eidos), for example both are human being or horse” (GA 1.23.730b33–731a1).5
The difference between male and female is obvious to anybody, a general starting point with which Aristotle begins at the outset of the work. Animals can be seen to be male and female when copulating (GA 1.1.715a19) and by observable differences in their parts (GA 1.2.716a20). What is at first obvious to the senses, as Aristotle explains in his general work on the study of nature, is more knowable to us; we must start from here and work towards the more complicated, fundamental truths that are more knowable by nature (Ph. 1.1.184a10–21). The fact that the sexes are principles, archai, and the sense in which they are so, is less obvious; it is the aim of any natural investigation to reach an understanding of the principles (184a16). Aristotle works towards that goal by moving beyond the reproductive parts and focusing on male and female contributions to generation.
What follows describes Aristotle’s general theory of generation in terms of the differentiated roles of male and female. The chapter will then explain how this account is consistent with Aristotle’s later explanation of individual differences in animals that make them resemble members of their family (GA 4.3). A final section reflects on Aristotle’s sexism in his theory of generation.
Aristotle’s Theory of Generation
After providing a brief anatomy of the “nonuniform” generative parts (GA 1.3–16), following a similar methodology to On the Parts of Animals, Aristotle turns to the “uniform” generative parts, seed (sperma) and milk (GA 1.16.721a28–30). He concentrates in the main on sperma.6 This term is best translated as “seed” rather than “semen.” The term “semen” now means the fluid that carries spermatozoa, which only male animals produce. Sperma indicates that which is generative (GA 1.17.721b6–8) and is used ubiquitously in Aristotle and other contemporary theorists to refer to plant seeds and to what male and female animals contribute to generation (GA 1.17.721b8).7 In his account of mature adults at the prime of life, the uniform parts are those whose portions are homogeneous and borders amorphous; these are normally the main constituents of the nonuniform parts. For example, bone and flesh are the constituent parts of a hand (HA 1.1.486a5–14; PA 2.1.648a20–24). Unlike other uniform parts, seed is not, strictly speaking, the constituent of other body parts. Although the analysis requires investigations into the “chemical” makeup of the seed (GA 1.19, 2.2), the main focus of GA 1–2 is on making sense of seed as a cause of animate generation. With the static morphology of adult sexed bodies in place, we begin the more complicated account of the dynamic processes within and between these bodies that make it possible to generate another like in kind to the parents. Aristotle’s account of the action and powers of sperma is structured in two parts in Book 1; in the first, the origin of seed is argued for in a negative fashion by attempting to establish the implausibility of an alternative position. The second more constructive part argues that male and female produce different sorts of seed that play complementary roles in generation.
The Negative Argument for Blood-Derived Seed
Aristotle refers to his rivals only by the nondescript “some people” (tines). This group, according to Aristotle, claim that sperma comes from “the whole of the body” (GA 1.18.721b9), meted out part by part (GA 1.18.722a16–b30). It is possible that Aristotle groups together many different views that share that general feature in order to avoid more intricate discussions and disagreements. If the idea of an opponent, for example, were that the fluid humors condense to form the sperma, as we find in certain Hippocratic texts, then this view is more plausible than the vaguer idea that the whole body is productive of seed.8 Aristotle notes that the rival view tries to explain resemblance to parents and why a new animal has parts that are like those of the adult. He attacks it in a number of ways, most importantly for being unable to explain the organizing force in generation – if the parts are separated out in the sperma, why would they all come together in the right order (GA 1.18.722b4–7)? This insight offers important support for his views on the differentiated roles of the sexes, to which we will return shortly. The other argument points to the difference between putrefaction (a sort of rotting) and concoction (a sort of cooking). Aristotle understands the rival view to be that the parts of the body of the parent are undergoing putrefaction to produce sperma, and since nothing natural can come to be via rotting (GA 1.18.725a1–10), their view is implausible.9 Instead, sperma is produced through concoction, which is effected by the animal’s nutritive soul. As was already established in On the Parts of Animals, blood is the product of nutrition, created by the concocting action of the soul; this blood is the internal nourishment that goes to make up all the parts of the body of the particular animal in question (PA 2.2; Juv. 2).10 Sperma, Aristotle declares, is concocted blood, and since it is (as blood) intended to travel towards (and thus construct and facilitate the functioning of) all the parts of the body, it is emphatically not coming from these parts. Thus, we reach Aristotle’s ingenious and hugely influential blood-based (or haematogenetic) theory of seed, which will end up holding sway in Arabic and Latin medio-philosophical traditions in the West.11 Concoction (pepsis) is a term that occurs often in Aristotle’s biology, indicating a constructive process.12 However, the further concoction of the blood to produce sperma in animals appears not to be the beginning of construction but a heightening of the potential for form present in the blood. This “final nourishment” has been cooked up by the nutritive soul of that particular animal to be able to become all its parts, in the right order and with the correct functions.13 This, Aristotle tells us, is a useful residue of nutritive processing, rather than the useless residues discarded as such.14
Differentiated Roles for Male and Female
Having established the origins of sperma, Aristotle next sets out to argue that female animals have a different sort of sperma from males and that, properly speaking, the female variety is not actually generative (at least not as far as current observations indicate).15 The female is unable to concoct the nourishment to its final form, that is, the white ejaculate of the male.16 What the female contributes ends up less concocted than the male sperma, and oozes into the uterus, waiting to become the body of the offspring; its bloody nature is quite evident when it leaves the body as menstrual discharge (GA 2.4.738a14–15). We might wonder, says Aristotle, why the female does not generate an animal on its own, given it has a generative residue, and also a place to gestate the fetus (GA 2.5.741a6–9). This must be because it lacks the archê – start or principle – of the soul of the new animal, which is supplied exclusively by the male. For, not only is it empirically evident that female animals do not generate fully without male intervention (GA 1.21.730a29–30, 2.5.741b5–6, 3.1.750b27–29), but this also makes sense in terms of final causes, because “otherwise the male would exist for no good reason and nature does nothing in vain” (GA 2.5.741b4–5).
Another argument for the differentiated roles of the sexes takes us back to Aristotle’s debate with his rivals, their position being implausible because it does not supply any organizing principle in generation. The rival position also fails to explain why there are two sexes; if both sexes have sperma that contain all the parts of offspring, then copulation would result in two animals, one from the female and another from the male. Instead, the resultant animal is an organized combination of the two (GA 1.18.722b7–9). For Aristotle, this is best articulated from a broad metaphysical viewpoint. The coming to be of a new animal is a change in the category of substance, and substantial change is a transition from something that is potentially to something that is actually what it is. This requires, on the one side, a passive capacity to change and, on the other, an active capacity to change; the female contribution is the one and the male the other. There is a single joint actualization (GA 1.21.729b9–18). This also means that the male is, properly speaking, more of a generator than the female, because it is through its organizational agency that generation is brought about, similar in some sense to what a craftsman (dêmiourgos) achieves.17
There is some debate about whether Aristotle thinks that females contribute sperma.18 Many like to contrast his position with those, like the Hippocratics and Galen, who hold to a “two seed” theory of generation and thus present Aristotle as a “one seed” theorist. But evidence from all of his works shows that Aristotle considered the female generative residue to be a sort of sperma. The next section will reinforce this view by providing a way to unify the theoretical content of the treatise On the Generation of Animals.
Aristotle on Female Sperma and the Coherence of the GA
Does the female contribute sperma? The best way to answer this is in the typically Aristotelian manner: in a way, yes, and in another way, no. If by sperma one means the agent, what Aristotle calls the efficient cause, that “by which” generation is effected (GA 2.1.733b33), then no the female does not. But if what is meant is a genuine generative contribution, originating in the actions of the nutritive soul of the parent, which strives to make another like in kind, then she does contribute sperma, and sperma that is crucial to the successful outcome of generation. For Aristotle the female does not contribute crude or raw materials to generation. Her blood-derived residue has been concocted by her nutritive soul to go towards, constitute, and maintain all the functioning parts of her body (GA 2.4.738b8–9, 740b19–20, 3.11.762b2–3). If the male’s sperma provided all the specifications that make an animal the way it is (like the old-fashioned understanding of a genetic code) it could mate with any female that produced a residue in its uterus, so long as it was around the same size and had the same gestational period as its usual female counterpart. But when this hybridization does happen, as when a male dog mates with a female fox, the offspring is not a replica of the male but has half of its parts from the dog and half from the fox (2.4.738b29–30), since the material that the female supplies is importantly species-specific.
The difference between male and female contributions, Aristotle’s “differentiated two seed theory,” is that the female seed supplies the materials and body of the offspring while the male seed provides the principle of soul.19 The best way to understand the male role is as the source of substantial generation; it is “the start/principle of the change/motion” (hê archê kinêseôs). When the Greek word in that phrase, kinêsis, is translated as “motion” and the metaphor of the craftsman emphasized, Aristotle’s theory has been interpreted as the male semen being full of movements which fashion the embryo.20 But kinêsis can also be translated as “change” and indicates that the male or his instrument, semen, is the efficient cause (otherwise known as the moving cause) of generation. Change here is not local motion but the change from the not being to the being of a substance.21 As the efficient cause of the generation of an animal the same in kind or form, the male contribution is part of a teleological structure; it is the proper efficient cause, aimed at that end. The female contribution lacks this, but is the proper material cause, and is thus also part of the same teleological structure; it is the matter whose end is to become the functioning living body of an animal of that particular kind.22
Aristotle explains the female incapacity as the inability to complete generation.23 Some female animals can produce so-called wind eggs, which have some differentiation and a degree of life or soul (GA 1.21.730a30–33, 3.1.750b9). Despite this ability, such females can never produce a living animal without having mated with a male (GA 2.3.737a30–34, 2.5.741a15–21, 3.1.750b27–30, 751b23–26). The wind egg, although on its way toward a living being, does not have its own soul and cannot nourish itself, and so it fails to continue to develop. This failure to generate can be traced back to the female animal’s own soul, which, as part of its generative function, attempts to produce another like in kind to the self, but fails due to relative lack of physiological heat.
As the start of the change, the active agent of that change, the male, is the principle (archê) of generation in the strictest sense; but this is not a result that the male animal can ever bring about on its own without the female. There is, indeed, an interdependency; the female is a complementary “principle” (archê) of generation (GA 1.2.716a5–6). Rather than offering this dynamic perspective on the process of substantial generation and the complementary roles of the contributions of the sexes to that outcome, Aristotle’s theory is often characterized in a static manner as involving the contributions of “form” from the male and “matter” from the female. This is also usually expressed as the male transmitting or imposing form on the matter, which can lead to difficulties understanding Aristotle’s account of hereditary resemblance.24 In the next section I will explain how concentrating on male and female as form and matter and the male as a set of motions or movements clashes with his theory of heredity; these problems are not, however, insurmountable.25
Aristotle’s Theory of Hereditary Resemblance
The male, according to Aristotle, contributes no material or bodily part to his offspring (GA 1.21.729b18–20). After having opted for this position at the end of Book 1, Aristotle raises various potential puzzles, aporiai, arising from it at the beginning of Book 2. The immateriality of his contribution is particularly challenging given Aristotle’s view that soul and body (form and matter in animals) are part of a unit and metaphysically inseparable (soul is the actuality or activity of the body that is potentially living, De an. 2.1). Furthermore, an agent of change is normally in physical contact with that which they are changing, as is evident in the comparison case of the carpenters, whose hands and/or tools must touch the materials in order to produce the given results (GA 2.21.729b15–18, 1.23.730b10–31). In response to this problem, Aristotle posits that there is contact at the outset but that the effects of this are ongoing after contact has ceased (the male leaving nothing material in the offspring). He offers another comparison to help make sense of this: the “spontaneous puppet,” an ancient device or toy that produced a number of movements after one initial trigger.26 That the tools males as agents employ (or their bodies in the case of insects) are no longer in physical contact must allow for the offspring to come to resemble the individual male parent; the effect on the materials is to make an animal of a certain type but also to make this particular animal here. In order to understand this aspect of generation, Aristotle turns to the causes of sex difference and heredity in Book 4 of On the Generation of Animals. The male contributes the efficient cause, but he is also an individual; like an individual carpenter, his action brings along with it his own personal influence.27 Thus, as well as making sure that the animal is like in kind or form (for example, human being or horse), the male also conveys “potentials” (dunameis) related to subspecies differences, that is, being male and being a particular individual with peculiar parts and aspects (GA 4.3.767b23–26). When these dunameis are activated due to the state of the “proportional blend” (summetria) of the sexes’ contributions, changes can be brought about that shape the offspring to be male and resemble the father.28 The female contribution to generation also conveys potentials relating to the female sex and the individual female parent which are able, under certain circumstances, to activate changes within them that shape the offspring accordingly.29
Aristotle’s theory of generation, when it has received attention from philosophers, has tended to be viewed as problematic because of a perceived difficulty with reconciling his account of hereditary resemblance with the differentiation of male and female roles.30 These perceived difficulties are most apparent when Aristotle’s theory is summarized as the male transferring form to the female matter. If form is then also taken to represent every specification, every shape or nuance of the offspring, then that makes it impossible to see how the offspring could resemble the female. If male contributes form (and no matter) and the female matter (and no form) how could they possibly both contribute the same thing, the capacity to shape parts to resemble them?
This difficulty is resolved by carefully considering Aristotle’s earlier account of the generative contributions of both parents as residues of nutrition. Both the male and female sperma are going towards and able to become like all the parts of their individual bodies – and so it is easy to see how these can combine to produce an offspring with parts of both. The capacity to form the parts is contained in both blood-derived contributions. As for the problem of their providing metaphysically nonoverlapping roles (as matter and form), it is better to think of them as contributing in complementary ways as material and efficient causes and thus sharing certain characteristics of the kind, and aiming for the same end (telos).31 We have already seen how, in the case of hybrid animals, Aristotle has no difficulty with the female animal’s contribution to generation determining the shape and appearance of her offspring. The dog/fox combination will look partly like the vixen. We can think of the kinêseis which bring about resemblances as neither form nor matter but as per se causes; they relate to the parent as an individual generator.32 The fact that the male contributes to individual features of the new animal has led some to question Aristotle’s commitment to essentialism. As the male contributes the form, won’t he contribute an “individual form” with specifications for him as an individual?33 The havoc this wreaks on Aristotle’s philosophy is considerable, and unjustified by the evidence.34
The first portion of On the Generation of Animals (up to the end of Book 3) follows a certain sort of essentialism. Generation is described in terms of generating another like in form or kind to the parent (GA 2.1.732a1–5). Aristotle seeks to elucidate the process in a general manner, covering as many animals as possible (PA 1.4.644a24–648b8). For all animals, the male and female contributions are efficient and material causes; for all animals, the embryo develops in the stages described in GA 2.6. Differences occur between broader groupings or between kinds of animal. For example, those animals that produce “perfected eggs” have their uteri high up in their bodies, whereas those that produce “imperfect eggs” have theirs lower down (GA 1.8.718b22–25). When the broader explanations do not cover all cases, and a narrower group is explained separately, the procedure almost always bottoms out with atomic species.35 And so Aristotle is faithful to the idea that there are essential kinds. This allows him to focus on teleological explanations in Books 1–3. From the beginning of Book 4, however, a different type of discussion begins; because Aristotle strives in this section of the treatise to explain subspecies differences, explanations are not offered solely in terms of essentialism and teleology.36 As his focus turns to particular instances, the discussion includes the causes of differences that occur below the level of species. All human beings have eyes (the development of which generally fits to GA 2.6.743b33–744a11, 744b4–11), but Boudicca has blue eyes and Nefertiti brown eyes. Going back to the idea that both male and female contribute blood-based residues, Aristotle now explains that these fluids contain other powers or capacities. These powers or capacities are activated in generation, producing differences in body parts. For Aristotle, the capacities in the bodily fluids that maintain specific body parts are prepared to battle with the counterpart capacities of the other parent. This battle is expressed in terms of mastering (kratein) and being mastered (krateisthai) (GA 4.3.768a3–5, 768b7–8).37 These mechanisms in the blood-derived generative fluids, although not related to teleological causation, are not chance-like (tuchon) (GA 4.3.768a3). There is an order to how this occurs.
The differences between individuals, as between Boudicca and Nefertiti, are due to neither the material nor efficient causes of the substantial generation of the kind – which are, strictly speaking, the male and female roles in generation according to Aristotle (GA 1.18.724a35–724b12, 1.20.729a9–12). But both male and female animals have particular bodies with specific processes occurring in them by which they maintain their parts and nourish themselves; thus, when they interact to produce the new animal, these capacities come into play to establish that new individual’s particular body.
Concluding Remarks on the Sexism of Aristotle’s Account of Animal Generation
Aristotle’s theory is undoubtedly sexist and possibly even perniciously so, depending on what sort of indirect effects one imagines it to have had (Reference ConnellConnell 2016: 33–34). Aristotle was obviously hugely influential in the history of Western thought, even if his zoological treatises were not central to his later reception.38 The hierarchies relegating women to a lesser status, sometimes thought to be ingrained in Western metaphysics, are arguably in line with Aristotle’s view that women are lesser human beings, incomplete men, striving but failing to fully concoct generative seed.39 Some have argued that Aristotle was forced into having a sexist view of generation since metaphysically only one parent could be the agent of the generation of an integrated substantial entity.40 It seems highly implausible, however, that metaphysics led him to conclude that the male played this superior role.41 The ultimate reason for sex difference is so that the superior can be separated from the inferior, the active from the passive, the essence from the lowly materials it uses to achieve its greater actuality (GA 2.1.732a3–9).
Though we can safely say that Aristotle viewed females, and so of course also female humans, as lesser beings, and detailed this inferiority in terms of a failure to generate, it is important to resist an exaggeration or distortion of this truism. One example of such distortion is when Aristotle is taken to espouse the view that men (and all male animals) achieve, or at least attempt to achieve, their superiority by generating an offspring identical in every way to themselves.42 This has been challenged by careful readings of the texts and taking into account the full scope of his account of generation. If resemblance to female relatives were a deviation from an ideal, it would be seen as a “monstrosity” caused by a malfunctioning of the mechanisms that should have produced a male like the father. But there is no account of that sort in GA 4.3 where maternal influences (i.e. kinêseis) are introduced as “an independent source of inheritance” (Reference HenryHenry 2006a: 278–279). Furthermore, when particular individuals are shaped like one or other parent (or their grandparents) this is not what makes them the sort of animal they are, human being or horse. And this is what is crucial about generation, that another animal the same in form as the parents develops. In each particular instance of generation, changes can happen in which we switch the source of the shaping powers from those of the individual male to those of the individual female. When a female comes to be rather than a male, arguably something of value has been lost.43 But when the animal comes to resemble the female more than the male, there is no reason to think it to be a less successful member of its kind than any other male. So long as the new animal has normal functional parts, it does not matter which of its relatives it looks like.44
Another misunderstanding worth mentioning is the idea that the male’s active role in copulation has something to do with their biological superiority for Aristotle.45 While in some places it is said that the male sperma is further concocted by the action of the penis (GA 1.5.717b23–24), this is not a general feature of his theory of the male role in generation. In many cases, it is not sexual actions that concoct the semen, but the warm nature of the male system, which makes the sperma ready to emit when encountering a female.46 Aristotle believes that in some sorts of animal, males do not have penises (GA 1.5.717b14–16, 7.718a17–20). Insects also do not produce semen, and so neither penis nor semen are required for the male to bring about generation.47
Despite his underlying biases, the comprehensiveness of Aristotle’s zoological research led him to acknowledge the value and importance of the female in nature. In those animals that are hermaphrodite, such as bees, containing within themselves both male and female principles (3.10.759b30), the female tasks are prominent.48 The womanly ruler bees are treated as worthy of respect as pseudo-royal personages (GA 3.10.7–13). In other animals, the female is larger (PA 4.8.684a20–22, GA 1.16.721a19–21, HA 5.11.538a22–27) and braver (HA 8(9).1.608a34–35) than the male. The parenting skills of female animals are usually superior, such as in deer (HA 8(9).5.611a15–23), she-bears (6.611a33–35), female cuckoos (29.618a26–29), and birds in general (GA 3.2.753a10–13). These skills are forms of intelligence, mimicking human varieties (HA 7(8).1.588a29–31).49
Aristotle makes patently obvious by his constant observations of the production, raising, and training of young that many animals would not survive or thrive without the female of the kind. While some might argue that female animals are mere tools for male reproductive success on Aristotle’s view, what he actually says is that male and female animals must work together since generation “concerns them both” (GA 2.1.732a11).50 It would be a very odd position indeed for half of the instances of a given kind to be mere tools for the other half.51 The parts, activities, character, and way of life (HA 1.1.), which is what make a particular type of animal what it is, are found in the female of the kind, at times to a heightened degree than in the male. For example, the female Laconian hound is “better formed by nature” (euphuesterai) than its male counterpart (8(9).1.608a28). Alternatively, one could argue that what is characteristic of the kind as a whole is a combination of features from female and male. For example, where legs are placed in viviparous quadrupeds depend on female tasks, that is, suckling the young (IA 12.711b29), whereas some defensive parts, like horns, occur only in the males (HA 4.11.538b15–20). For Aristotle, male is superior to female but this doesn’t render the male complete without the female. The idea that both sexes are part of the kind in question is apparent in much of Aristotle’s research on animals and ought to be acknowledged alongside his hierarchical view of the sexes.52
