Aristotle on the Beginning of Animal Life and Soul Activities

2.1 Embryo Formation, the Creation of the Heart, and Substantial Generation

As many commentators have pointed out, the heart (or its counterpart) plays a central role in Aristotle’s theory of embryogenesis. He emphasizes that the heart is formed at the beginning of gestation (cf., e.g., II.4, 740a1-23; II.5, 741b15-24), and he often refers to the heart as the ἀρχή (e.g., II.4, 738b16-7; 740a17-8; II.5, 741b15-6).^[5] To establish the primacy of the heart, Aristotle occasionally appeals to empirical observation (Juv. 468b28-30; HA VI.3, 561a6-12). He also argues that an embryo must engage in nutrition, which in turn requires that the heart be present from the beginning, manage nutritional processes, and provide nourishment, i.e., blood (GA II.4, 740a17-23). Aristotle presents this argument in direct response to Democritus, who suggests that the external parts of animals develop before the internal ones (II.4, 740a13-15). This view, Aristotle argues, does not only contradict empirical evidence according to which the heart is present from the beginning of gestation (II.4, 740a4-5), but also misses the point of what it means to be an animal. As he says, Democritus seems to be talking about “animals from wood or stone” that have no such principle, whereas “all animals have it, and have it within them” (740a15-17).^[6]

In addition to being required for nutrition, Aristotle is clear on the point that the heart (or its analogue in bloodless species), which is the first to develop in an embryo, is also the primary organ or source (τὴν ἀρχὴν) of the perceptual soul (GA II.6, 743b25-6; Juv. 468b28-ff; 474a25-ff). And touch (along with its derivative, taste), the most basic sense shared by all animals, has the heart as its proper organ (Sens. 438b30-439a3; Juv. 469a10-ff; PA II.10, 656a27-31). The heart is also the source of all further perception (PA III.4, 666a11-18). Thus, the heart not only equips the embryo with its own principle of nutrition, but also functions as a perceptual organ that corresponds to its animal soul.

While commentators widely agree that the heart has to be formed early on, some think that it is not present from the very beginning.^[7] In particular, it has been suggested that the initial formation of the new embryo does not yet bring about a heart or any other organ, but only “a functional, structured body”.^[8] This interpretation is well in line with views according to which the initial result of conception is not yet an animal properly speaking but a plant-like living being, which may have an animal soul potentially but not yet actually.^[9] We will return to such interpretations below. For now, it is important to acknowledge that in GA II.4, where Aristotle gives the most detailed descriptions of embryo formation in blooded animals, he presents it as involving primarily the formation of a heart. In this chapter, Aristotle mentions two concrete parts belonging to the animal resulting from conception: there are membranes (ὑμένες, χόρια: 739b31) that separate the solidified part from the liquid, and, more importantly, the ἀρχή or heart emerges as the embryo’s first functional organ (739b34-5; 740a1-4). He explains that the primacy of the heart is not just evident from empirical observation, but required by reason, because the heart is the principle that enables the newly created animal to manage the subsequent growth and development of the body independently of its parents:

For this reason, the heart is set apart (ἀποκρίνεται) first in actuality (ἐνεργείᾳ). And this is not just apparent to the senses (for it happens like this), but also to reason. For once that which was formed is set apart from both parents, it must manage itself, just like a son moves away from his father into a separate house. So that it must have a principle, out of which also later the regulation of the body comes about for the animals. … Because of this, the heart is first manifestly distinct for all blooded animals; for it is the principle both of the uniform and of the non-uniform parts. For it is already worthy of being called the principle of the animal and of the organized whole (σύστημα) as soon as it needs nourishment. For of course the animal grows.^[10] Nourishment of an animal is the ultimate blood and its equivalent. The vessel of these is the veins. Therefore, the heart is also the principle of them. (GA II.4, 740a3-23)

The passage emphasizes that once conception is complete, not the parents (i.e., external causes) but the embryo’s inner principle controls all further processes, in particular its growth. Aristotle’s emphasis on growth further indicates that, after the creation of the heart, we are no longer dealing with the generation of the embryo, but with its further development. Embryo formation is thus the significant substantial change after which the newly generated being has retained its ontological status as an animal, i.e., a being that manages its further development by itself.

Of course, the embryo does not come into being instantaneously, at the very moment the male (or its semen) comes in contact with the material provided by the female. Aristotle explicitly says that it takes some time to create an embryo, and that the duration of that process depends on the specific animal in question. Kinds of insects in which the male directly works on the female secretion without emitting semen create the new embryo during copulation. For this reason, they copulate “for a long time” (GA I.23, 731a15), namely for “a certain part of a day” (I.23, 731a19), until the embryo is formed. Immediately after copulation, insects release small larvae (I.21, 729b30-32). As Aristotle makes clear elsewhere, larvae are insects in their first embryonic state (III.9, 758b6-28).^[11] For animals that emit semen, copulation is much shorter. It lasts until the male animal has emitted semen. Subsequently, the semen works on the menstrual fluid and thereby creates the new embryo within days (I.23, 731a20). After accomplishing this task, “the body of the semen is dispersed and evaporated” (τὸ σῶμα τῆς γονῆς διαλύεται καὶ πνευματοῦται, II.3, 737a11-12). Aristotle’s remarks on the duration of embryo formation clearly shows that there is a definite time mark when the generation of the embryo is finalized.

2.2 The Significance of Aristotle’s Terminology

In his discussion of embryo formation in viviparous blooded animals in GA II.4, Aristotle first describes the semen’s action on the menstrual fluid, and then calls the immediate result of this process an “animal” (ζῷον: II.4, 739b30).^[12] That Aristotle deliberately describes newly formed embryos as animals is confirmed by HA VII.7, where he discusses embryonic development in human pregnancies. There, he describes newly formed embryos as being enveloped by membranes in the womb, and says, in this context, that “at first the animal is generated” (πρῶτον … γίνεται τὸ ζῷον) inside the deepest membrane. The context of the two passages is similar; in both, Aristotle explains that newly formed embryos need to be separated from the fluids in the uterus. Arguably, this is true not only for newly formed embryos, but also for embryos at later developmental stages. The word “animal”, thus, might be taken to refer to newly formed as well as later ones. But even if the passage can be taken to be in principle about both, it is important to note that Aristotle does not terminologically distinguish between them, which is what we would expect him to do if his view were that newly formed embryos are not yet animals.^[13]

In a longer passage in GA II.1, where Aristotle compares the reproductive processes of different kinds of animals, he says the following:

There are, then, some animals which are not formed from seed, as I have also said earlier. But all blooded ones are formed from seed, as many as are formed as the result of copulation, with the male emitting semen into the female; when it has entered, the animals (ζῷα) are set and take on their peculiar shape, those that are viviparous within the animals themselves, the others in eggs [and seeds and other such secretions] (GA II.1, 733b16-23, trans. following Peck).

Aristotle says here that, in the case of blooded animals, the new animals are set when the semen enters the female. Since the passage mentions animal generation in connection with the assumption of their specific shape, Aristotle’s reference to “animals” might be taken to describe, not the immediate products of conception, but rather embryos once they have attained their species-typical appearance at a later developmental stage. But the context of the passage, which discusses copulation and the entering of the semen, might suggest that Aristotle’s description does not focus on those later stages, but instead on the very first setting of the embryo. Thus, in this passage, “animals” can be taken to refer to embryos at the beginning of gestation.

Aristotle extends the view that newly formed embryos are animals to oviparous animals and insects. In III.2, 753b10-11 (cf. 16, 22) he refers to a newly formed embryo inside an egg as an “animal”, in a context that is focusing on the beginning of the formation process (cf. 730b15-16). And, as we will show in Section 2.3, Aristotle describes larvae, i.e., the immediate products of conception in insects, as creatures with the equivalents of hearts and the corresponding animal functions such as locomotion, which should make them qualify as animals as well.

In Aristotle’s natural theory, the term ζῷον does not refer to the broad class of living beings that also includes plants, but is explicitly restricted to beings with sense perception.^[14] In DA II.2, 413b1-4, Aristotle says that whereas living (τὸ … ζῆν) belongs generally to things that are alive (τοῖς ζῶσι), “something is an animal (ζῷον) primarily in virtue of perception”. In DA II.3, 414b1-5, he emphasizes that plants only engage in nutrition, whereas animals (ζῷα) have at least one sense, i.e., touch (cf. II.2. 413b4-9).^[15] In his biological works, he standardly restricts the term ζῷον to living things that have sense perception, and hence are animals in the proper sense of the word. In his definition of animals in Sens. I, 436b10-12, he states that animals qua animals have sense perception and differ from other beings with regard to this feature. At Juv. 467b22-5, he argues that plants, though alive, are not ζῷα. In the Generation of Animals, he remains consistent with this terminology. In GA II.1, 732a11-13, he says that whereas all living things (including plants) live by virtue of “participation in the female and the male”, only animals have sense perception. In II.3, 736a30-31, he says that animals have a perceptual soul, by contrast with wind eggs (cf. 736b1; III.7, 757b15-19). When comparing animals to plants, he emphasizes that even the lowest degree of perception qualifies something as an animal (I.23, 731a33-b5). That Aristotle sometimes uses the word “ζῷον” to characterize newly formed embryos thus provides evidence that he thinks of them as percipient beings.

2.3 Complete and Incomplete Animals; Complete and Incomplete Embryos

Aristotle sometimes describes embryos as incomplete animals (GA II.4, 737b8-25; GA II.1, 733a32-b16). For example, in the context of discussing reproduction in insects, he points out that a larva is a “complete embryo”, but “not yet a complete animal” (κύημα τέλειον ζῷον δὲ μήπω τέλειον: II.4, 737b9). This has been taken to imply that embryos are only potential animals.^[16] However, as we shall see, Aristotle’s description of embryos as incomplete animals in fact supports the view that they count as actual animals, for him.

Aristotle introduces the distinction between complete and incomplete animals in a passage where he describes a hierarchical order among animals. On Aristotle’s theory, the place of an animal species on the scala naturae corresponds to the level of perfection or completion of its offspring once it is released.^[17] Blooded viviparous animals, which have the highest rank, release complete offspring that is already “similar to itself” (II.1, 732a25-6) and “complete … in terms of quality” although not in terms of quantity (II.1, 733a33-b3). By contrast, animals of lower ranks, which are oviparous or larva-producing, release their offspring while it is still “unarticulated” (ἀδιάρθρωτον) and has not yet reached its final shape (μορφή: GA II.1, 732a25-28).^[18] Their offspring is incomplete in the sense that, at the time it is released, it is still in its embryonic stage and has not yet reached its species-typical appearance.^[19]

When Aristotle describes larvae and other embryos as incomplete animals, he indicates that they are animals, but emphasizes that they need further development before they can count as a proper member of their species. When analysing the reproduction of insects, Aristotle points out that they go through three stages — larva, pupa, insect (cf., e.g., III.9, 758b27; 759a3-7) — and emphasizes that the respective animal reaches its completion in the third and final stage, which implies that it is already an animal, if an incomplete one, in the first two stages (GA II.1, 733b13-16; GA III.9, 758b24-28).^[20] More importantly, larvae and other embryos are not “incomplete” animals in virtue of lacking a perceptual soul; to the contrary, Aristotle’s descriptions underline the fact that they must have bodies that correspond to a perceptual soul.^[21] For example, he says that embryos are perfect whenever they are male and female (GA II.4, 737b10-11). Since an animal’s sex is determined by its heart (or its equivalent), complete embryos will necessarily have that organ (GA IV.1, 766a34-b5).^[22] Moreover, Aristotle says that larvae are “moving things” (III.9, 759a4: κινουμένων), in the context of describing them as “taking nourishment” (λαμβάνουσαι … τροφὴν) before they turn into pupae, and comparing them to eggs, which also take nourishment and grow (αὐξάνεται), up to a certain point (758b29-36).^[23] The initial movements of larvae, then, are associated with their life activities, presumably instances of locomotion with a view to gathering and absorbing food. But they can only exhibit such movement provided that they possess the necessary functional organs, among others the equivalent of a heart, which Aristotle identifies as the origin of all movement (cf. PA II.1, 647a24-6; III.3, 665a10-15; III.4, 666b14-15). In Aristotle’s psychological theory, life functions such as growth and locomotion, whenever they occur together, are actualizations of an animal soul. The fact that Aristotle ascribes both of these activities to newly formed embryos must mean, then, that they have such a soul, for him.

Aristotle’s distinction between complete and incomplete embryos further confirms that “incomplete”, in his terminology, does not imply “potential”. “Incomplete embryos,” for him, are not, as the term might be taken to imply, beings on their way to becoming live embryos. Rather, he uses the term to designate unviable embryos, such as wind-eggs, which at GA III.7, 757b18-19 he calls “incomplete” precisely because, unlike larvae, they are not alive and cannot grow or develop.^[24] Thus, for Aristotle, incomplete embryos do not possess any potential for further development.

3.1 Actual and Potential Soul in GA II.3

In GA II.3, 737a16-18, Aristotle says:

Περὶ μὲν οὖν ψυχῆς πῶς ἔχει τὰ κυήματα καὶ ἡ γονὴ καὶ πῶς[/πως] οὐκ ἔχει διώρισται· δυνάμει μὲν γὰρ ἔχει, ἐνεργείᾳ δ’ οὐκ ἔχει

This text is often taken to mean that both embryos and seed have soul only potentially, and not actually. For example, Platt translates the sentence as follows:

It has been settled, then, in what sense the embryo and the semen have soul, and in what sense they have not; they have it potentially but not actually.^[25]

In a comment, Platt adds that “this sentence is misplaced, but one cannot say where it should go”.^[26] This comment is warranted, given Platt’s translation. As Carraro notes, whereas in GA II.1, 735a4-9 Aristotle expressly asks whether or not seed (there, τὸ σπέρμα) has soul, and answers conclusively that it both has and is soul in potentiality (καὶ ἔχει καὶ ἔστι δυνάμει), extending that claim to the case of embryos “is more surprising”.^[27] However, the text in 737a16-18 does not seem to be misplaced on the following alternative translation, which therefore is preferable:

Therefore, concerning soul, it has been determined how the embryos have it and the semen also in a way does not have it; for it [sc. the semen] has it potentially, but it does not have it in actuality.

On this reading, the sentence summarizes two views that have already been established previously in GA, namely, both (1) that semen has soul in potentiality, as already concluded in II.1, 735a4-9, and (2) that the embryo has soul in actuality, as has been argued in II.3 736b8-13 (see Section 3.2 below).

One might object that Aristotle cannot view embryos as having a soul in actuality, at least as early as they are formed, because he is explicitly committed to the idea that “nature simultaneously (ἅμα) assigns to each [living thing] the capacity (τὴν … δύναμιν) and the organ (τὸ ὄργανον), for it is better thus” (GA IV.1, 766a5-6).^[28] And so, the objection would run, Aristotle must think that an embryo does not possess in actuality either the nutritive or the perceptual capacities of the soul until it possesses all the organs by means of which those soul capacities are to be exercised. However, it is difficult to see how Aristotle could consistently think of embryos as being only potentially ensouled while also ascribing to them the actual performance of life activities like nourishing, growth, or perceiving. For Aristotle, it is by the soul functioning as cause that anything partakes of these activities (cf., e.g., DA II.4, 415b21-416a8; 416b9-11). His theory simply does not accommodate the occurrence of such an activity except as the exercise or actualization of a corresponding soul capacity.^[29] The conclusion to draw is that, as soon as embryos are formed, they possess a soul in actuality, and their performance of life activities is due to that fact.

It has been suggested that for Aristotle embryos “do not possess the nutritive soul in actuality because they live like plants and, thus, do not exercise the nutritive capacity in the way that is appropriate for animals”.^[30] However, for the reasons given above, the very exercise of nutrition by embryos implies that they do possess the nutritive soul in actuality, whether or not they live like plants, in Aristotle’s view (and we shall see that they do not below; cf. Section 4.1). It may still be argued that the soul of embryos is fundamentally different from that of animals and is perhaps akin to that of plants. But that assumption, which brings forth problems of its own,^[31] is unneeded. For there are reasons to think that Aristotle, contra Carraro, cannot maintain that being unable to exercise life functions “in the way that is appropriate for animals” should deny embryos the possession of animal souls in actuality.

Aristotle notes that in the case of many animal species (e.g., fox, bear, lion) members are at birth “unarticulated” (ἀδιάρθρωτα), in many species the newborn are blind, and some birds are born without nostrils and ears (GA IV.6, 774b5-775a3). If having a lion soul in actuality requires performing life functions “in a way that is appropriate for a lion”, then a newborn, developing, and blind lion would not count as having a lion soul in actuality.^[32] Unless one is willing to accept that implication in the case of a newborn member of a species, one should not accept the equivalent implication in the case of embryos.^[33] It is reasonable to suppose, then, that Aristotle thinks embryos all along possess animal souls in actuality.^[34] Otherwise, one would be confronted with the problem, approximating a sorites paradox, of determining the point at which an embryo possesses enough functional organs and corresponding capacities to count as an animal, a task no less daunting, it seems, than attempting to determine a particular point in an organism’s development at which it should count as a member of an animal species (a question that is beyond the scope of this paper, if it can be answered conclusively at all).

A further reason to think that Aristotle in GA II.3 means to attribute animal souls to early embryos appears in the subsequent chapter. In II.4, Aristotle compares early embryos (i.e., embryonic hearts, prior to the development of any other bodily part) and the emergence of blood-vessels in them to sown seeds and the growth in them of roots and shoots (739b33-740a4). In this context, he states that the heart is the principle “of the animal, or the composite, whenever it requires nourishment” (τοῦ ζῴου καὶ τοῦ συστήματος ὅταν δέηται τροφῆς), and speaks of blood or its analogue as the ultimate nourishment “of an animal” (ζῴου) (740a20-21). He then goes on to say the following (740a24-7):

τούτων δ’ ἀγγεῖον αἱ φλέβες· διὸ ἡ καρδία καὶ τούτων ἀρχή. δῆλον δὲ τοῦτο ἐκ τῶν ἱστοριῶν καὶ τῶν ἀνατομῶν. Ἐπεὶ δὲ δυνάμει μὲν, ἤδη ζῷον ἀτελὲς δέ, ἄλλοθεν ἀναγκαῖον λαμβάνειν τὴν τροφήν· διὸ χρῆται τῇ ὑστέρᾳ καὶ τῇ ἐχούσῃ ὥσπερ γῇ φυτόν, τοῦ λαμβάνειν τροφὴν ἕως ἂν τελεωθῇ πρὸς τὸ εἶναι ἤδη ζῷον δυνάμει πορευτικόν.

And of these [viz. of blood and its analogue] the blood-vessels are a container. For this reason, the heart is their principle. And this is clear from the studies and the dissections. And since [the blood-vessels] exist in potentiality, and an animal is at this time imperfect, it is necessary for it to take in nourishment from elsewhere. For this reason, it makes use of the uterus, and the [mother] having it, just as a plant [uses the] earth, for the sake of taking in nourishment until it would be perfected toward being an already potentially mobile animal.

Translators often take δυνάμει … ζῷον ἀτελὲς to be predicated of “foetus” or “embryo”, even though the last occurrence of κύημα appears only quite earlier, at 740a1-4.^[35] There, Aristotle makes the point that all organs exist in some sense potentially in an early embryo, with the heart being the first to be “set apart” in actuality — a fact that he goes on to elaborate on down to the passage quoted above.

Reading αἱ φλέβες along with δυνάμει at 740a24, apart from making better grammatical sense and avoiding the problem of squaring this line with Aristotle’s unqualified references to an embryo as an animal,^[36] also fits in better with the overall argument in this chapter. The blood-vessels that Aristotle at 740a24 says exist potentially are those that he goes on to specify in the following lines, namely, “the two primary blood-vessels” emerging from the heart and the “blood-vessels going away from these toward the uterus — what is called the navel” (740a27-30).^[37] Upon birth, once nutrition is no longer supplied to the embryo via the umbilical cord, the blood-vessels constituting the cord are compressed (συμπίπτουσιν) (IV.8, 777a25). And, at GA II.7, 745b22-746a2, Aristotle expressly associates the transition into independent nutrition, marked by the umbilical blood-vessels ceasing their operation as conveyers of nutrients from the uterus to the embryo, with the perfection of the animal, as we have suggested he implicitly does at II.4, 740a24-7.^[38]

The claim that the blood-vessels connecting an embryo to the uterus, despite functioning along with the heart in the nutritive processes of early embryos (cf. 739a35-8), are animal blood-vessels of a newborn animal only in potentiality, is directly relevant to defending Aristotle’s view that no organ apart from the heart exists in actuality at that stage. Aristotle’s comparison of the way in which such embryonic potential blood-vessels convey nutrients derived from the mother to the way in which plant roots convey nutrients derived from the earth, at 740a25-6 (cf. 739a36-8; 740a33-5), also indicates that he thinks of early embryos as animals in 740a24-7. The embryo, once connected to the uterus, depends on it for nutrition, and Aristotle points out that the umbilical blood-vessels, once formed and used for that purpose, have the potentiality to transform and be used for the self-sustaining nutrition of the animal upon birth.^[39] But the embryo itself is, at the outset, already an actual animal, albeit an “imperfect” one.^[40]

3.2 The Nutritive Soul and Its Activity in Embryos

A further remark in GA II.3 suggests that Aristotle takes embryos to possess the nutritive soul in actuality. In 736b8-13, he says that:

Τὴν μὲν οὖν θρεπτικὴν ψυχὴν τὰ σπέρματα καὶ τὰ κυήματα τὰ χωριστὰ^[41] δῆλον ὅτι δυνάμει μὲν ἔχοντα θετέον, ἐνεργείᾳ δ’ οὐκ ἔχοντα πρὶν ἢ καθάπερ τὰ χωριζόμενα τῶν κυημάτων ἕλκει τὴν τροφὴν καὶ ποιεῖ τὸ τῆς τοιαύτης ψυχῆς ἔργον· πρῶτον μὲν γὰρ ἅπαντ’ ἔοικε ζῆν τὰ τοιαῦτα φυτοῦ βίον.

It is clear, then, that the seeds and the separate embryos should be supposed to have the nutritive soul potentially, but not to have [it] in actuality before they draw up nourishment and perform the function of the soul of such a kind, exactly as the separated of the embryos do. For at first all such things seem to live a life of a plant.

Aristotle says here that, whereas seeds and separate embryos both have the nutritive soul potentially, the separate embryos, in addition, have the nutritive soul in actuality. The identity of the “separate embryos” in question is controversial. But, since the reading above suggests that Aristotle in this passage is interested in contrasting seeds with embryos in general (rather than contrasting seeds and “unseparated” embryos with “separated” embryos), the reference seems to be to embryos, which are generally speaking separate, by contrast to seeds, which are not.^[42] In the next chapter, Aristotle, discussing the formation of the embryo, says that “the heart is set apart (ἀποκρίνεται) first in actuality (ἐνεργείᾳ)” (II.4, 740a3-4; cf. 740a17-18: διωρισμένη), with each of the other parts subsequently being separated (χωρίζηται: 740a9-13). By contrast to seeds, which are parts of the original organisms generating the new animal (i.e., the parents), the embryo is an entity “set apart in actuality” from the earliest stage of its very formation, and it is called “separate” on that account.^[43] Indeed, the emergence and development of the embryo’s parts immediately following the formation of its heart, as well as the growth of such organs (cf. GA II.4, 740a3-23; Section 2.1 above), already constitute an exercise of its actual nutritive soul (cf. Section 2.1 above).

Furthermore, Aristotle has a special reason to refer to the embryos that he is contrasting in this passage with seeds as “separate embryos”. At GA I.20, 728b32-4, he says that, in those beings that have life but in which the female and the male are not separate, “the seed is so to speak an embryo” (τὸ σπέρμα οἷον κύημά ἐστιν). And at I.23, 731a1-4, he again says that plants, in which the female and male are not separated, emit, not semen, but rather “an embryo, the ones called seeds” (κύημα τὰ καλούμενα σπέρματα). At II.3, 736b8-13, therefore, Aristotle must clearly distinguish the seeds/embryos of plants and unisex animals from “the separated of the embryos” — the embryos of those animals in which male and female are distinct and in which seeds and embryos are clearly marked off from one another. Embryos in this latter class, he thinks, are “separated” and have the nutritive soul in actuality.

It may be objected that the reading above attributes to Aristotle a claim that is either absurd or redundant. For, if X is actually F, then it is unreasonable to say that X is simultaneously F potentially (because X’s potentiality for being F is already being actualized), unless what one means by saying so is simply that in order for X to be F actually X needs to be such as to be capable of being F in actuality (in which case no new information is added by saying that X is also F potentially). But Aristotle’s usage of similar language elsewhere suggests otherwise.^[44] In PA II.3, 649b16-17, he says that, when taken out of a mixture of earth and water, water is both potentially and actually (καὶ ἐνεργείᾳ καὶ δυνάμει) moist. Water is actually moist on its own, but it also contains the potentiality of making moist a mixture combining it and another (dry) component. Put more generally, Aristotle’s view is that in at least some instances a thing X has a property F actually while also having F potentially insofar as X, differently configured (e.g., mixed with other components, having developed, or having undergone some other process of change), would possess that same property F actually. When Aristotle says, in GA II.3, 736b8-13, that embryos both actually and potentially have the nutritive soul, then, his point seems to be that an organism, at its earliest embryonic stage, is in possession of the nutritive soul in actuality, but is also capable of undergoing a change process (here, specifically, development into a member of an animal species, such as “horse”) at the end of which it — the developed organism — would have that soul in actuality as well.^[45] If this is correct, then there is no reason to think that Aristotle thinks embryos might “exercise life functions like nutrition and even perception” while also thinking that they have “a merely potential soul”.^[46]

The interpretation above requires that Aristotle think that there is a fundamental function actually fulfilled by the nutritive soul in embryos, and which persists in the newborn animal (in addition to new types of function or activity only added at that later stage). In GA II.3, 736b8-13, Aristotle does say that embryos (in general, given our reading above) “draw up nourishment and perform the function of such a [sc. the nutritive] soul”. One might take the καὶ in this sentence epexegetically, in which case the activity of drawing up nourishment itself would constitute the primary function for which the nutritive soul is responsible, perhaps in addition to growth, which is closely related to it. But it might be objected that this activity takes radically different forms in embryos and in newborn animals, such that it could hardly be said to persist between the embryonic and postnatal stages.^[47] Indeed, Aristotle argues that the nourishment of embryos resembles that of plants (GA II.4, 740a24-31). Similarly, he likens the growth of embryos, “which comes to be through the umbilical cord”, to the growth of plants coming to be “through the roots” (GA II.4, 740b8-10). Lastly, as mentioned above, already at formation, and prior to taking in nourishment from the uterus through the umbilical cord in the way that Aristotle describes as “plant-like”, embryos already actively engage in rather different nutritive processes — they develop and grow parts, particularly the blood-vessels by which they are to be subsequently connected to the uterus and draw nutrients from it.

Thus, one might do well to appeal to an even more basic function for which the nutritive soul is responsible. In DA II.4, 416b17-19, Aristotle refers to the nutritive part of the soul as its “primary principle” (ἡ … τῆς ψυχῆς ἀρχή) because it is a capacity “to preserve that which has it qua the kind of thing that it is”. Such a function, at least, seems basic enough to apply, in full, to the embryo (at all stages) and the newborn animal alike.^[48]

4.1 Early Embryonic Sleep and Perception

That embryos for Aristotle are capable of sense perception and indeed actively engage in it ought to be uncontroversial.^[49] In GA V.1, he says plainly that animals first acquire perception (αἴσθησιν) within their mother (778b22), and that embryos are observed to be periodically awake (779a7-9) — a state that for him necessarily and essentially involves actively perceiving (Somn. 454a1-7). There are, however, questions about the time at which that soul capacity and its activity become available to embryos. Aristotle presents this as the “puzzle” of whether it is sleep or waking that comes first at “the beginning of the generation” (τῆς ἐξ ἀρχῆς γενέσεως) of an animal (778b23-5). Sleep comes out on top, since wakefulness is more frequent in later stages of development and because sleep is an intermediate state between being and non-being (778b25-31). The problem Aristotle faces here is that on the one hand embryos seem to be continuously asleep from the point they first acquired perception (778b21-23), while on the other hand perception usually takes place during waking periods (778b31-2). After laying out the problem, he says the following (778b31-779a4):

τῷ γὰρ ἐγρηγορέναι τὸ ζῆν μάλισθ’ ὑπάρχει διὰ τὴν αἴσθησιν. εἰ δ’ ἐστὶν ἀναγκαῖον ἔχειν αἴσθησιν τὸ ζῷον, καὶ τότε πρῶτόν ἐστι ζῷον ὅταν αἴσθησις γένηται πρῶτον, τὴν μὲν ἐξ ἀρχῆς διάθεσιν οὐχ ὕπνον ἀλλ’ ὅμοιον ὕπνῳ δεῖ νομίζειν, οἵανπερ ἔχει καὶ τὸ τῶν φυτῶν γένος· καὶ γὰρ συμβέβηκε κατὰ τοῦτον τὸν χρόνον τὰ ζῷα φυτοῦ βίον ζῆν—τοῖς δὲ φυτοῖς ὑπάρχειν ὕπνον ἀδύνατον· οὐθεὶς γὰρ ὕπνος ἀνέγερτος, τὸ δὲ τῶν φυτῶν πάθος τὸ ἀνάλογον τῷ ὕπνῳ ἀνέγερτον.

For living belongs mostly to waking on account of perception. And if the animal must have perception, and it is an animal then when perception first comes to be, one should think that the condition at the beginning is not sleep but similar to sleep, of a kind such as the one that the genus of plants has too. For the animals at that time happen to live a life of a plant. And it is impossible for sleep to belong to plants, for no sleep is unbroken by waking, and the affection of plants that is analogous to sleep is unbroken by waking.

Aristotle has been taken here to mean that “the initial state of embryos does not even deserve to be called sleep”, so that the instances of perception he considers later in the chapter follow a period of time during which “the embryo is not able to perform any perceptive activity”.^[50] This reading suggests that the initial state of embryos does not only preclude active sense perception but denies them the status of percipient beings altogether. But the passage suggests otherwise.

The condition that Aristotle ascribes to embryos “at the beginning” is a special kind of sleep, surely, because there is no waking state to contrast with it during that time. It is in this regard that the sleep in question is plant-like, because plants are never awake. Aristotle says at the beginning of this passage (and consistently with his overall view) that an animal counts as such only when it is percipient. And, in the very sentence that compares newly created embryos to plants on the basis of their continuous sleep, he calls such embryos “animals” (τὰ ζῷα) and clearly contrasts that term there with “plant” (φυτοῦ) (779a1), as he generally does (see Section 2.2). Therefore, the comparison to plants cannot have the purpose of denying embryos the status of animals, and thus the capacity for sense perception. To the contrary, Aristotle’s view must be that newly created embryos are animals having perceptual souls from the moment of their creation, despite the fact that they are not awake for some time. Indeed, Aristotle thinks of sleep as being essentially a feature of animals. He defines sleep as a “lack of motion” of and “a kind of fetter” on sense perception (Somn. 454b25-6), and he points out that it affects the heart (Somn. 458a25-32). Sleep, properly speaking, cannot be attributed to living beings devoid of sense-perception.

Of course, embryos could be percipient living beings in virtue of having perceptual souls, and not exhibit active sense perception. But in GA V.1, Aristotle goes further. Immediately after the passage quoted above (778b31-779a4), he presents empirical evidence for the view that sleep is compatible with active sense perception. First, he reminds us that newborn animals, and in particular human infants, cry and laugh during their sleep, which is evidence for actual sense perception taking place: “for perceptions occur also in sleeping animals, and not just what we call dreams, but also others besides dream” (779a12-14). And second, he points out that people who sleepwalk have perceptions of their surroundings just as if they were awake. Both phenomena show, in his opinion, that newborn animals and human infants who spend the greater part of their time asleep can nevertheless engage in perception. As he explains, they “seem to be perceiving and living in sleep, just as being ignorant of waking” (779a19-21). This statement can easily be applied to newly formed embryos as well.^[51]

In conclusion, Aristotle’s view that newly formed embryos are asleep rests on his assumption that they are percipient beings. Moreover, his observation that sleep is compatible with actual sense perception allows for the possibility that they actively perceive while asleep.

4.2 The Embryonic Heart and Its Perceptual Activities

In a passage where he specifies the heart as the source of touch and all further perception (PA III.4, 666a11-18), Aristotle supports his position using the following claim (666a20-21):

ἐν γὰρ τοῖς ἐμβρύοις εὐθέως ἡ καρδία φαίνεται κινουμένη τῶν μορίων καθάπερ εἰ ζῷον

For in embryos straightaway the heart is manifestly moving, of all the parts, exactly as if it were an animal.^[52]

The facts that the movement of the heart indicated here is supposed to explain the status of the heart as the source of sense perception, and that the relevant feature of it in this respect is that it is animal-like, signal that for Aristotle the embryo, from its earliest stages (i.e., when the only bodily part it has is the heart), engages in perception.

Aristotle also notes in the History of Animals that the heart is moving in its own right from the very beginning. In the passage in question, he describes his experiment of opening chicken eggs after three days and three nights. At that time, the heart of the embryo is the size of a “speck of blood” (στιγμὴ αἱματίνη) and jumps and moves around “as if it were ensouled” (ὥσπερ ἔμψυχον: HA VI.3, 561a11-13). The use of ὥσπερ in this text is certainly not meant to question the fact that there is an actual soul involved. Rather, it is meant to compare the embryonic heart with a small (post-embryonic) animal.^[53] Aristotle’s main point here seems to be that at this early stage one can observe, not only that the heart has already been formed (a fact he stresses also elsewhere), but also its characteristic activity. And since the life activities of such an early embryonic heart include autonomous and lively movements, it resembles a small living (post-embryonic) creature.

Similarly, when Aristotle says, in PA III.4, 666a20-21, that the heart behaves from the very beginning “as if it were an animal”, or when he goes on to say at 666b16-17 that the heart “is naturally akin to some animal” (οἷον ζῷόν τι πέφυκεν),^[54] he presumably means to liken the heart to an insect, a bird, or a small mammal, and thus to a fully developed member of a particular species whose characteristic behavior we observe more readily and regularly. The analogy with mature members of a given animal species indicates that the active perception of early embryos consists in the exercise of their perceptual soul, which they possess in actuality, as is standardly the case with animals exercising life activities, for him.^[55]

Aristotle does not specify the nature of the perceptual activities available to early embryos. Since he thinks of embryos as animals, and since he thinks that all animals have at least the sense of touch, he should attribute at least tactile perception to them. Indeed, his theory leaves room for attributing to early embryos actual instances of tactile experience. For Aristotle, as we have seen, embryos from their very formation possess a heart, which functions as the primary organ of the sense of touch. In addition to the role of the heart in touch, he thinks, flesh functions as the medium in the activity of that sense (cf. DA II.11). And he says that the embryo from its inception is “fleshy” (κρεῶδες) (HA VII.3, 583b10), and features membranes (ὑμένες) (GA II.4, 739b31), presumably surrounding the heart.^[56] Early embryos therefore seem to satisfy Aristotle’s criteria for, and for him may well actively exhibit, at least a rudimentary type of tactile perception.

But early embryonic instances of touch may differ radically from later ones, given the physiological differences between early embryos and (say) mature animals, similarly to the difference between embryonic and postnatal nourishment.^[57] And so, even if early embryos do exhibit a form of tactile perception, one may do well to appeal to a more basic perceptual function that they share with animals at later stages of their development.^[58] A plausible candidate for such a function, given Aristotle’s psychology, would be subjective awareness, which is arguably the product of the perceptual capacity whenever it occurs, including in instances of human intellectual activity.^[59]

In Section 3.2, we have argued that Aristotle in GA II.3, 736b8-13 attributes to embryos both a potential and an actual nutritive soul, since an early embryo both actively exercises its nutritive capacity and would, given its successful development, eventually exercise the nutritive capacity of the animal species to which it would belong. These successive nutritive capacities, for Aristotle, differ radically, but they nevertheless also share a basic function in common. We are now in a position to attribute to Aristotle a similar view with regard to the perceptual capacity. On that view, an embryo about to develop into a horse, say, has the perceptual soul both actually and potentially. Actually, because it has a functioning perceptual soul performing the fundamental function of awareness (in addition, most probably, to the exercise of a basic form of tactile perception), and potentially, because it is not yet the horse (e.g.) that would have a perceptual soul featuring that fundamental function alongside additional ones — both those characteristic of later animals in general (a more advanced form of touch) and those specific to the species to which it belongs (the rest of the senses, if the species in question happens to have them).

5.1 Embryos and Plants

As we have seen in Section 4.1, Aristotle in GA V.1 compares the initial embryonic state resembling sleep to the life of plants. This comparison, which recurs in other places in Aristotle’s corpus, may seem to imply that he denies embryos animal status. In fact, however, the import of the analogy is quite different. In HA VIII.1, 588b4-23, Aristotle says that the differences between inanimate natural things and living things, and the differences between different life forms, are sometimes subtle to the point of being indiscernible in practice. Thus, there are difficulties in determining whether some marine organisms, for example, are to be classified as either animals or plants. And, generally, different living things exhibit “life” and “movement” to varying degrees, and “according to minute difference” (588b21-3). Given these considerations, there seems to be ample room for comparing certain animals to plants, and this is particularly true for embryos, and generally for animals at the earliest stages of their development. Aristotle thinks that embryos initially only have rudimentary perceptual functions, much more basic than those of adult animals, especially animals of higher species (see Section 4.2). He also thinks that at the beginning embryos are permanently in a state akin to sleep, and only perceive during that state (see Section 4.1). For this reason, he repeatedly compares embryos to plants. Embryos, like mollusks, would be comparable to plants because of their relative lack of movement and perception. But, as Aristotle points out in his comparison between plants and animals in GA I.23, 731a25-731b7, even the most basic forms of sense perception, touch and taste, which “seem to be like nothing” when compared to wisdom (φρόνησις), are in fact “wonderful when compared to a plant or a stone” (731b1-2).

The comparison between the uninterrupted sleep-state of newly created embryos and the life of plants in GA V.1, then, highlights the point that sense perception in newly formed embryos is extremely limited. Since it takes place during a sleep-state that appears to be initially uninterrupted by waking periods, the condition of early embryos in fact closely resembles the life of plants. But the fact that embryos share some commonalities with plants does not mean that they lack perceptual souls and therefore are plants. This is also evident on the basis of passages where Aristotle draws a comparison between sleeping humans and plants. In EE I.5, 1216a2-9, he says that living a life of uninterrupted sleep (ἀνέγερτον ὕπνον) is no different from “living [while] being a plant” (ζῆν ὄντα φυτόν).^[60] He goes on to say that plants seem to partake of such a life, and so do children, who “from their first generation in the mother” (κατὰ τὴν πρώτην ἐν τῇ μητρὶ γένεσιν) are asleep the entire time. Here, the sleeping condition of children is explicitly likened to the condition of embryos, and both are compared to the condition of plants. The comparison, then, cannot be meant to deny perception to the comparanda. Similarly, in NE X.6, 1176a33-5, Aristotle says that if happiness were a condition of the soul, it would have belonged to a person who spent their entire life sleeping, “living the life of plants” (φυτῶν ζῶντι βίον). Again, though a life of a plant is explicitly attributed to that hypothetical person here, surely this is not meant to deny that person a perceptual soul.^[61] Likewise, when Aristotle likens animal nourishment to that of plants, in PA II.3, 650a14-31,^[62] the animals in question are mature members of their species. Thus, his comparisons of embryos to plants do not imply that he views embryos as non-animals.

5.2 The Comparison to a Mass of Bronze in Metaph. Θ.7

In Metaph. Θ.7, Aristotle raises the question “when each thing exists potentially (δυνάμει) and when not” (1048b37). He illustrates the issue as follows:

οἷον ἡ γῆ ἆρ’ ἐστὶ δυνάμει ἄνθρωπος; ἢ οὔ, ἀλλὰ μᾶλλον ὅταν ἤδη γένηται σπέρμα, καὶ οὐδὲ τότε ἴσως;

For example, is earth a human being potentially? Or not, but rather more so whenever seed already comes about [alt. whenever it already becomes seed], and perhaps not even then?

Whereas earth certainly is not yet potentially a human being, Aristotle says here, seed might be. Later in the chapter, discussing specifically things having an internal principle of generation, Aristotle returns to the example mentioned above, and says the following (1049a14-18):

οἷον τὸ σπέρμα οὔπω (δεῖ [εἶναι]^[63] γὰρ ἐν ἄλλῳ καὶ μεταβάλλειν), ὅταν δ’ ἤδη διὰ τῆς αὑτοῦ ἀρχῆς ᾖ τοιοῦτον, ἤδη τοῦτο δυνάμει· ἐκεῖνο δὲ ἑτέρας ἀρχῆς δεῖται, ὥσπερ ἡ γῆ οὔπω ἀνδριὰς δυνάμει (μεταβαλοῦσα γὰρ ἔσται χαλκός).

This text may be translated as follows (henceforth, reading 1):

For example, the seed [is] not yet [a human being] (for it must [be] in another and change), and when it is already of such a kind through its own principle, it is this potentially. But that requires another beginning, just as earth is not yet potentially a statue (for, having changed, it will be bronze).

This reading of the text, similarly to numerous previous translations,^[64] takes it to convey the idea that seed is not yet potentially a human being, but that it will be so, upon undergoing the appropriate process of material change eventuating in an embryo, just as earth is only potentially a statue once it has changed into bronze.^[65]

Because on this reading Aristotle likens the embryo about to develop into a human being to the mass of bronze about to be sculpted into a statue, it might seem to suggest that he similarly regards the embryo as matter of the relevant quantity and kind, to be shaped into a human being at some later stage.^[66] But that need not be the case. In GA II.3, in the context of discussing the development of seeds (σπέρματα) and embryos (κυήματα), Aristotle says that

an animal (ζῷον) and a human being do not come to be at the same time, nor do animal and horse, and similarly in the case of the other animals, for the end comes to be last, and the characteristic mark of each is [the] end of generation (736b2-5).

In the immediately preceding line (736b1), which is supposed to be explained by 736b2-5,^[67] Aristotle specifies that “ζῷον” refers to a being endowed with, and defined by, the perceptual soul (τὴν αἰσθητικήν).^[68] He seems to think, then, that the formation of a human being (or a horse) is preceded by a stage at which the embryo counts as a percipient pre-human (or pre-horse) animal. To return to Metaph. Θ.7, 1049a14-18, on reading 1 Aristotle might mean there that seed is not yet potentially a human being because it must first develop into an embryo, which in turn would be potentially a human being, but which itself would also already have its own form, i.e., the soul of a percipient pre-human living thing.

It is not clear, furthermore, that one must accept reading 1, or, generally, the understanding of 1049a14-18 as mapping the development of a seed, through an embryo, to a human being, onto the creation from earth first of bronze and finally of a statue. Alternatively, one could translate these lines as follows (henceforth, reading 2):

For example, [earth is] not yet the seed (for it must [be] in another and change), and when it already is of such a kind through its own principle, it is already potentially this. But that requires another beginning, just as earth is not yet potentially a statue (for, having changed, it will be bronze).

On this reading, Aristotle in these lines returns to the question raised at the beginning of the chapter, of whether seed, unlike earth, can already be said to be a human potentially, and answers it in the affirmative. Earth, when it is “in another” — presumably, as earthy matter inside the human body^[69] — can change and morph into seed, at which point it would be of such a kind as to constitute a (further) human being potentially.

It may be argued against reading 2 that, if a seed already is potentially a human being, then the embryo, which results from that seed, ought to already count as a human being, and that this would be inconsistent with Aristotle’s view in GA II.3, namely that there is an intermediate stage between the seed and the human being at which the embryo exists as “an animal”. There are at least two possible responses to that worry. First, a seed and the embryo resulting from it could both qualify as a potential human being, albeit at different levels of approximation to that final product. To return to Aristotle’s own analogy, on this proposal the seed and the embryo would count as a potential human being in the same way that a randomly shaped lump of bronze and a quantity of bronze already assuming the preliminary shape of the sculptor’s work would both count as a potential statue. Second, human beings are not mentioned anywhere in Metaph. Θ.7, 1049b14-18. And so, even though it is likely that this passage hearkens back to the previous discussion of whether seeds count as potential human beings at 1048b37, the discussion at 1049b14-18 might focus on a specific part of the development of a seed into a human being. Thus, when Aristotle at 1049b14-18 speaks of the seed as potentially this, he may have in mind an “animal”, an “embryo”, or a “substance”, rather than specifically a “human being”.

Reading 2 offers several advantages over reading 1. First, the earlier occurrence of the example of embryogenesis in Metaph. Θ.7 (at 1048b37) discusses the status or role of both earth and seed in that process. And the discussion in 1049a14-18, on reading 2 and by contrast to reading 1, again mentions both earth and seed, and thus corresponds more closely to 1048b37. Second, on reading 2, Aristotle compares the relation between earth, seed, and human to the one between earth, bronze, and statue, respectively. It seems reasonable for that comparison to be made, inter alia, because earth is the first item on both lists (and serves as the starting point in both of the change processes corresponding to these). Finally, whereas reading 1 takes Aristotle to be drawing an analogy between bronze (of whichever shape) and an embryo having its own specific form (the form of a percipient pre-human animal, to follow the interpretation offered above), this discrepancy is avoided by reading 2, on which bronze is likened to seed.

We need not determine conclusively whether one of these possible readings is preferable over the other. For our present purposes, it is sufficient to note that, on either reading, Aristotle may well consider the embryo a percipient living thing. On reading 1 (and the interpretation of it proposed above), the embryo, which is taken to be a potential human being, is conceived of as a pre-human percipient animal, following Aristotle’s view in GA II.3. On reading 2, it is seed that is said to be a human being potentially, leaving room for the view that the development into an embryo would include a further step toward the actualization of that potentiality, or at any rate the possession by that embryo of at least a perceptual soul.