Aristotle on Human Being as an ΕΙΔΟΣ and a Collection of ΕΙΔH^*

Aristóteles sobre o ser humano como um ΕΙΔΟΣ e uma coleção de ΕΙΔH

ABSTRACT

This paper focuses on the pivotal question concerning the human eîdos in Aristotle’s natural and political philosophy: whether the human eîdos is divisible or indivisible for Aristotle? If the human eîdos is divisible, why does Aristotle claim that human being is an éschaton eîdos which admits of no differentiation? But if it is indivisible, why does Aristotle claim that the city is composed of human beings who “differ in eîdos”? I answer the question by distinguishing between two kinds of human eîdos as actuality in Aristotle: the human eîdos as first actuality (human eîdos_A1) and the human eîdos as second actuality (human eîdos_A2). I argue that human eîdos in the sense of human eîdos_A1 is indivisible for Aristotle, but in the sense of human eîdos_A2, it can be divided into multiple eidē which are manifested in various human functions and ways of life.

Keywords:
Aristotle; human eidos; potentiality; actuality

RESUMO

Este artigo concentra-se na questão central sobre o eîdos humano na filosofia natural e política de Aristóteles: o eîdos humano é divisível ou indivisível para Aristóteles? Se o eîdos humano é divisível, por que Aristóteles afirma que o ser humano é um échaton eîdos, que não admite diferenciação? Mas, se é indivisível, por que Aristóteles afirma que a cidade é composta por seres humanos que “diferem em eîdos”? Respondo a essa questão distinguindo dois tipos de eîdos humano como atualidade em Aristóteles: o eîdos humano como primeira atualidade (eîdos humano_A1) e o eîdos humano como segunda atualidade (eîdos humano_A2). Argumento que o eîdos humano, no sentido de eîdos humano_A1, é indivisível para Aristóteles, mas, no sentido de eîdos humano_A2, pode ser dividido em múltiplos eidē, que se manifestam em diversas funções humanas e modos de vida.

Palavras-chaves:
Aristóteles; eîdos humano; potencialidade; atualidade

1 Introduction

According to Aristotle’s general account, the human being is an ἔσχατον εἶδος which admits of no differentiation (PA 1.4.644a23-33; HA 1.6.490b16-19; cf. Metaph. Γ.3.999a5-6).¹ That is to say, unlike the εἶδος of birds which can be further divided into various εἰδή, the εἶδος of the human being is indivisible. It follows that all human beings shall have only one and the same εἶδος, viz., the εἶδος of the human being (Metaph. Z.8.1034a5-8). Yet many passages in the Aristotelian corpus seem to contradict this claim. In Long. Vit. 1.465a4-7, for example, Aristotle claims that things “differ according to γένος” when they differ as human being to horse, but “according to εἶδος” when they differ as human being to human being” (κατ' εἶδος δ' ἄνθρωπον πρὸς ἄνθρωπον). Elsewhere, in the Politics 2.2, it is said that the city is composed not only of a number of human beings, but of those who “differ in εἶδος” (εἴδει διαφερόντων) (1261a22-24).

The aporia lies in whether Aristotle is committed to the “single human εἶδος thesis” (hereafter SHET) that there can be only one indivisible and undifferentiated εἶδος (viz. species-εἶδος) for all human beings, or the “multiple human εἰδή thesis” (hereafter MHET) that there can be various sub-εἰδή for one single human εἶδος. Both theses, in regard to textual evidence, have their pros and cons. SHET, for example, is supported by the decisive accounts in Categories and the central books of Metaphysics, but runs into difficulties in explaining the political inequalities among various human groups in the Politics. MHET, on the other hand, fits with Aristotle’s biological and ethico-political accounts, but is contradicted by Aristotle’s pivotal claim that there cannot be any formal difference between human beings qua human being (Cat 5.3b33-34; 5.3b37-38). In view of the difficulties, two divergent solutions have been put forward by Ward and Gallagher.² Ward, in favor of the orthodox view of SHET, argues that there are two kinds of deliberation (what she calls the “everyday type” and the “specialized type”) in Aristotle. All human beings (including men and women, free and slave), on Ward’s reading, “engage in the everyday type of deliberation” and thus can be said to possess the per se property of human being. The human being, in this sense, remains a synonym, viz. a single εἶδος, for Aristotle.³ Gallagher, on the contrary, attends to the view of MHET by ascribing to Aristotle a doctrine of particular forms. According to Gallagher, the human γένος is “composed of a multiplicity of human εἰδή [particular forms]”. The so-called single human εἶδος is only “that which is common to all εἰδή within the γένος, viz. a core εἶδος”. So, there is nothing contradictory in saying that Socrates and Callias both differ (in the sense of particular forms) and do not differ (in the sense of core form) in εἶδος.

In this paper, I will provide an alternative solution to the problem. I will offer a cohesive reading on which Aristotle is committed to both SHET and MHET. Specifically, I will distinguish between two kinds of human εἶδος as actuality in Aristotle: the human εἶδος as first actuality (hereafter human εἶδος_A1) and the human εἶδος as second actuality (hereafter human εἶδος_A2). I argue that human εἶδος_A1 is the human εἶδος as differentia (διαφορά), and human εἶδος_A2 is the human εἶδος as function (ἔργον) or way of life (βίος). Human εἶδος in the sense of human εἶδος_A1 is indivisible for Aristotle, but in the sense of human εἶδος_A2, it can be divided into multiple εἰδή which are manifested in various human functions (ἔργα) and ways of life (βιοῖ).

2 The Human ΕΙΔΟΣ is Indivisible

There is little doubt that εἶδος is used by Aristotle as a multivocal term (πολλαχῶς λεγόμενον).⁴ Hermann Bonitz, for example, summarizes in his monumental work the following groups of meanings of εἶδος: (1) the external shape; (2) the logical category “species” (in contradistinction to γένος); (3) the Platonic “Form”; and (4) the Aristotelian formal cause, the actuality, the essence (and so on).⁵ In what sense, then, is the human εἶδος indivisible for Aristotle?

Since the Platonic “Form” is excluded immediately, the first candidate seems to be the external shape. Can Aristotle mean that the human εἶδος is ultimate and indivisible because human beings cannot differ with regard to their external shapes or appearances? We find a relevant passage in Generations of Animals 4.3:

For what reason that the offspring is sometimes unlike any of these [ancestors] but still a human being, but sometimes, proceeding further on these lines, appears in the end to be not even a human being but only some certain animal, which is also called a monstrosity. (769b7-10).⁶

The interpretative issue of this passage is whether a human being of a monstrous shape is for Aristotle still a human being. Some commentators suggest that it is not.⁷ But there is no solid reason to think so. In the first place, Aristotle never claims that the offspring of a monstrous appearance deviates from its genus. Indeed, in 767b7, Aristotle seems almost to mean it by saying that “in [the cases of such monstrosity], nature has in a way deviated from the genus”.⁸ But the qualification “in a way”, τρόπον τινά, is important. It suggests that Aristotle doesn’t literally think the offspring of a monstrous appearance deviates from its genus. It deviates only “in a way”, that is, in regard to its external shape or appearance. Several lines later, in discussing the offspring who have the head of a ram or an ox (769b13-14), Aristotle further states that “in no case are they what they are said to be [viz. rams or oxen]”, but “resemblances only” (ἔστι δ' οὐθὲν ὧν λέγουσιν ἀλλ' ἐοικότα μόνον) (769b17). This is a further sign that the differentiations in one’s external shape or appearance have no effect, in Aristotle’s view, on one’s being. Finally, in 769b30, the monstrosity is classified by Aristotle as some kind of deformity (ἀναπηρία τίς). Insofar as other deformities, e.g. the female and the dwarf (GA 737a22; 749a4-6), are not deviations of the human genus, we have reason to think that the offspring with a monstrous appearance are not as well.⁹ It can be concluded, therefore, that when Aristotle claims that the human εἶδος is ultimate and indivisible, he cannot mean it in the sense of the external shape.¹⁰

The other option is the Aristotelian species. At first sight, it is perfectly sensible to think that the human εἶδος is ultimate and indivisible because the human being as a collective species is so. Yet there is a problem. For commentators have been more and more convinced that Aristotle’s biology does not have a taxonomy of fixed species as we do. That is to say, the terms γένος and εἶδος can practically function at any level of generality for Aristotle.¹¹ Being an Aristotelian species doesn’t entail that the species itself is indivisible. Under certain circumstances, an Aristotelian species can very well be an Aristotelian genus for further division (Phys. 227b11). Indeed, Aristotle has coined another term, “ἄτομος εἶδος” (indivisible species), that is proximate to our modern usage (cf. DA 414b27) and is employed in his description of human beings along with sparrow and crane (PA 644a29-32). Yet it is still not very telling. For to say that the human εἶδος is ἄτομος because it is an ἄτομος εἶδος is tautological. It leaves the question unanswered: why is the human εἶδος indivisible?

Now a γένος, according to Aristotle’s theory of division, can always be analyzed through division. It cannot be further divided if and only if there is no further differentia that can be taken or applied to it. In that case, it forms an ἄτομος εἶδος in the Aristotelian sense. So, if Aristotle holds the human εἶδος is an ultimate species, the differentia that isolates the human being from the other animals shall be ultimate (ἔσχᾰτος) and indivisible. What is that differentia? On the one hand, the differentia can be the combination of all the relevant differentiae that mark off the genus of human being from other animals (PA 643a7-643a31). But there is no evidence that such a differentia has ever been given by Aristotle.¹² On the other hand, the differentia can be an exclusive soul-capacity (DA 412a19-21; Metaph. 1037a28-31; 1038a25-6), viz. the human rational capacity which alone separates the genus of human being from other animals (Pol. 1253a9-10).¹³ For it describes, in Aristotle’s view, the substantial being or essence of the human being (Metaph. 1036a16-7; 1038a18-21; 25-26).

Now if the human rational capacity is, in Aristotle’s view, something that cannot be further differentiated, it is possible that when Aristotle claims the human εἶδος is indivisible, he means the human εἶδος as the ultimate differentia, the human rational capacity, is indivisible. But the problem is, Aristotle sometimes indicates that the human rational capacity is divisible. In NE 1139a5-6, for example, Aristotle claims the rational part (τό λόγον ἔχον) of the soul, in which the rational capacity is located, is capable of further divisions. It can be divided into two parts: the scientific part (τὸ ἐπιστημονικὸν) and the calculating part (τὸ λογιστικόν) (NE 1139a6-15). At other places, Aristotle suggests that the rational capacity can be divided by “the more and the less” (το μᾶλλον καὶ το ἧττον). Aristotle claims, for example, that the old are more practically-wise (σώφρονες) than the young (Rhet. 1390b5-6), and the male more than the female (Pol. 1277b25-29). Those remarks challenge our hypothesis that the human εἶδος is indivisible because the human rational capacity is indivisible for Aristotle. However, the hypothesis will remain intact. For, as I am going to suggest, (a) when Aristotle claims that the (rational) soul has sub-divisions, he only means it to be conceptual; and (b) when Aristotle suggests that the rational capacity can be divided by “the more and the less”, it is, in fact, not human rational capacity but human rational capacity with matter that is capable of further differentiation.

Let us first attend to the question whether Aristotle’s division of the (rational) soul is meant to be concrete or conceptual. By “concrete” and “conceptual” I mean the following:

1. X is a concrete part of Y iff X is a fixed part of Y (viz. having a fixed locus in Y) and can exist without Y.

2. X is a conceptual part of Y iff X is a functional part of Y (viz. as a functionally defined entity) and cannot exist without Y.¹⁴

On this view, a grain of wheat is a concrete part of a heap of wheat, for it can be either added to or detached from the heap. Curiosity, on the other hand, is a conceptual part of Socrates, for it is functionally defined and cannot exist without a subject such as Socrates. So, when Aristotle says that the (rational) soul has parts, which sort of part does he mean?

Three considerations suggest that Aristotle’s division of (rational) soul is conceptual. The first is the explicit statement Aristotle makes in DA 2.2. According to that statement, the human soul is not capable of spatial division, but conceptual division only (λόγῳ μόνον) (413b13ff). The second is the criticism Aristotle makes of the anonymous few (τινες) who hold that one can divide κατὰ τὰς δυνάμεις the soul into various concrete parts possessing capacities.¹⁵ According to that criticism, one will face two insoluble difficulties if one understands the soul-parts as concrete parts: the infinity and the inseparability of the soul-parts.¹⁶ Last but not least, Aristotle himself gives non-equivalent divisions of soul across the texts (compare, for example, the Nicomachean bipartite soul-divisions and the De Anima tripartite soul-divisions). If the Aristotelian soul-parts are meant to be concrete parts, it is difficult to see how those non-equivalent soul-divisions can fit in with each other. One objection toward this, however, is that Aristotle famously claims in DA 3.5 that the (active) intellect is able to exist without both the human soul and human body (DA 430a17-18; 430a22-23), which suggests that a soul part may be separable in a more-than-conceptual way. But in this case, when the active intellect is separate, it is already a soul rather than a part of soul.¹⁷ In other words, just like a hand when separate from the body is no longer a hand, the intellect separate from the soul is no longer the intellect as soul part - the intellect as soul part also comprises the passive intellect, which is perishable (DA 430a24-25). It seems that human intellect, as a capacity of soul, always exists together with all the other capacities of the soul. That’s why it is regarded as a part of the human soul rather than a soul.¹⁸ Taking all this together, it seems that the Aristotelian soul-parts cannot be concrete parts. And if so, the human differentia (viz. the rational capacity) remains substantially undifferentiated.

Now if the human rational soul-capacity cannot be divided in quality, we are left with the question whether it can be divided in quantity, that is, by “the more and the less”. Certainly, qualities in general admit of a more and less (Cat. 10b26-28). But the human rational capacity is not a quality simply.¹⁹ It is the ultimate differentia identified as the “substance and formula of a thing” (Metaph. 1038a20-21).²⁰ And the substance, in Aristotle’s view, doesn’t admit of a more and less: “if the substance is a human being, it will not be more a human being or less a human being either than itself or than another human being” (Cat. 3b34-39). On the standard Aristotelian account, therefore, two individual human beings shall not differ in degree with respect to human rational capacity. But if it is so, how shall one explain Aristotle’s occasional remarks that some human group differs from others with respect to some rational capacity, e.g. the practical rationality, that is, “the part of soul involved in opinion-forming” (μέρος τῆς ψυχῆς τοῦ δοξαστικοῦ) (Rhet. 1390b5-6; Pol. 1277b25-29)?

In Metaphysics H.3, Aristotle suggests a way in which the substance can admit of a “more and less”:

As number does not admit of the more and the less, neither does substance, in the sense of form (εἶδος), but if any substance does, it is only the substance which involves matter. (1044a9-11)

The εἶδος or substance in our present context is the human ultimate differentia, the human rational capacity. Here, in Metaphysics H.3, it is confirmed again that the ultimate differentia, the human rational capacity doesn’t admit of the more and the less. But in contrast to the Categories’ account, the Metaphysics’ account makes a huge qualification. It is said that though “with respect to the form” (κατὰ τὸ εἶδος) substance does not admit of a more and less, as “substance with matter” (ἡ μετὰ τῆς ὕλης) it might do so. That is, the rational capacity as the substance or essence of the human being cannot admit of a more and less, but when it is accompanied with some particular “matter”, it might do so.²¹ How does this shed light on our problem? Let us look at another passage in the Nicomachean Ethics:

One sign of what has been said is the fact that while young men become geometricians and mathematicians and wise (σοφοὶ) in matters like these, a young man does not seem to be practically-wise (φρόνιμος). The cause is that practical wisdom (φρόνησις) is concerned not only with universals but with particulars, which comes to be known from experience (ἐμπειρίας), but a young man is not experienced, for it is a long period of time that creates experience. (NE 1142a11-16)

The old are practically-wiser than the young not because the former have stronger rational capacity than the latter - for the young are at least equally wise in geometry and mathematics - but because the former has something that the latter doesn’t have, namely the long-time experience (ἐμπειρία) of the practical particulars (πράγματα). Those practical particulars are said to be the external objects of a certain sort of perception (1142a25-29), and perception, as Aristotle manifests in De Anima, cannot exist without the body (429b5). In other words, the practical wisdom is always related to body qua matter or, more specifically, to some particular body qua matter. Indeed, Socrates’s rational capacity qua form cannot differ from Callias’ by the more and the less, but Socrates’ rational capacity qua form with matter (viz. Socrates’ body) surely can. As a result, Socrates’ practical wisdom can differ from Callias’ by the more and less, even though with respect to form they do not differ in degree.²²

So far we have examined the materials that suggest the ultimate differentia for human being can be further differentiated for Aristotle. We have shown that none of them is conclusive. Aristotle’s claim, therefore, that the human εἶδος is indivisible can very well be founded on his usage of εἶδος as ultimate differentia. For the ultimate human differentia, the human rational capacity, is indivisible for Aristotle. In the next section, we shall move to consider another usage of εἶδος that Aristotle employs in his ethico-political works. On that usage, I argue, the human εἶδος is divisible.

3 The human ΕΙΔΟΣ is divisible

The main evidence suggesting that the human εἶδος is divisible for Aristotle chiefly appears in an ethico-political context. Aristotle claims, for example, in the Politics that a city is not a unanimous whole, but a whole composed of human beings who are different in εἶδος (εἴδει διαφερόντων) (Pol. 2.2.1261a22-24). By saying this, however, Aristotle doesn’t mean that a city shall be composed of human beings who are endowed with different kinds (εἰδή) of rational capacity. Rather, he is suggesting that a city should be composed of human beings who can perform different functions (ἔργα) or lead different ways of life (βίοι). A city of philosophers (viz. those who perform the function of contemplation and live a contemplative life) is strictly speaking not a city for Aristotle. It is an alliance (συμμαχία) which is useful only by its quantity - as “a greater weight is added to the scale” (Pol. 1261a24-27). But an alliance is not a city. A city, in Aristotle’s view, “is not any chance multitude, but one self-sufficient with a view to life” (Pol. 1328b16-17), that is, one necessarily constituted on the basis of the functions (ἔργα) that every city needs (Pol. 1328b15-16). As a result, there must be, says Aristotle, “a multitude of farmers, artisans, a fighting element, the well-off, priests, and those who decide about things just and advantageous” in the city (Pol. 1328b20-23). For the city, by its very nature, requires human beings to perform different kinds (εἰδή) of functions so as to achieve self-sufficiency.

By this account, therefore, we arrive at Aristotle’s second usage of εἶδος: εἶδος as function or way of life. On this usage, the human εἶδος is divisible because human functions or human ways of life are divisible. In Aristotle’s view, the city is built on the equality of distinct human functions that he terms “the reciprocity” (τὸ ἀντιπεπονθὸς) (Pol. 1261a30-31). No city can “come into being out of two doctors but rather out of a doctor and a farmer, and in general, out of those who are different [in εἶδος]” (NE 1133a16-18). A doctor and a farmer are different in εἶδος not because the human differentia (viz. the rational capacity) they possess are different, but because the human functions they perform or the human ways of life they lead are different. Their “formal differences” (εἴδει διαφερόντων) consist in their functions/ways of life other than their substances. This explains why Aristotle sometimes speaks as if some human being is “formally” superior to the other: the husband, for example, is superior to his wife. For though human beings qua human being do not differ from each other in differentia, they differ in functions, and their functions can be commeasured proportionally (NE 1133a31-1133b6). Accordingly, some human being (e.g. the husband) can be “formally” superior in proportion to another (e.g. the wife) without being “formally” different from the other. On my reading, therefore, Aristotle holds both an ontological egalitarian view and a functional inegalitarian view toward the human εἶδος: the human εἶδος as differentia is one and the same for every human being qua human being - for “the definition of man ought to be true of every man” (Top. 139a26) - but the human εἶδος as function or way of life can be hierarchically different for human beings qua wives, farmers, shoemakers, doctors, and so on.

Some clarification is, of course, needed at this stage. By function I mean neither the natural function nor the social function of human being. What I have in mind here is the specific function possessed by some specific human being or some specific group of human being. This sort of function is different from both natural and social functions of human being. For the social function of human being is determined by the social norm, and the natural function of human being is determined by the universal human differentia (viz. the rational capacity), but the specific function of a specific human being or human group X is determined by both the universal human differentia and X’s particular matter (viz. X’s body). Though the differentia is the same for all the human beings alike, the particular matter, viz. the body of some specific human being or some specific group of human being, is subject to many factors such as climate (Pol.7.7.1327b19ff) and habituation (Pol. 8.3.1338b4ff).²³

Now that people can differ with regard to their specific function/way of life is supported by many passages in the Aristotelian corpus. In Metaphysics I.9, for example, Aristotle raises the question why a female does not differ from a male in εἶδος (Metaph. 1058a29-32). The simple answer he gives is that the male-female contrariety is not in the formula (λόγος) of an animal (Metaph. 1058b1-3; 1058b21-23), and thus cannot be a proper differentia of the animal species. This is in accord with our reading. For it confirms that the husband as male and the wife as female are not distinct in εἶδος (for they, as male and female, share the same εἶδος as differentia for Aristotle). They are distinct only when they are not simply male and female, but are male and female who have functions (viz. the function of a husband and the function of a wife). Moreover, in Pol. I.13, when Aristotle tries to explain how the natural slaves, the female and the children, all being human beings, can differ with regard to deliberation (viz. an important aspect of human rational capacity) and virtues, he says:

For, if they have virtue, in what will they differ from freemen? On the other hand, since they are human beings and share in reason, it seems absurd to say that they have no virtue. A similar question may be raised about women and children, whether they too have virtues … So in general we may ask about the natural ruler, and the natural subject, whether they have the same or different virtues. For if both should partake in gentlemanliness, why should one of them always rule, and the other always be ruled? Nor can we say that this is a question of degree, for the difference between ruler and subject is a difference of kind, which the difference of more and less never is. Yet how strange is the supposition that the one ought, and that the other ought not, to have virtue … although the parts of the soul are present in all of them [men, women, natural slaves and children], they are present in a different way. For the slave has no deliberative faculty at all; the woman has, but it is without authority (ἄκυρον), and the child has, but it is incomplete. So it must necessarily be supposed to be with the virtues also; all should partake of them, but not in the same way, but to each in relation to his own function (πρὸς τὸ αὑτοῦ ἔργον) (emphasis added). (1259b26-1260a18)

If, Aristotle asks, all human beings partake in the same virtue or human εἶδος, why should one be superior to another? On the other hand, if some human being does not partake in human virtue or human εἶδος, why should he/she be called “human being”? The only way out of the dilemma, as Aristotle sees it, is to attribute different human εἰδή and virtues to different human beings. Certainly, Aristotle doesn’t mean by this that the human εἶδος can be further differentiated by another differentia and turns accordingly into many forms. Rather, he is using the human εἶδος in another sense, a sense that is related to the specific function of a specific human being: all the human beings share the same human differentia, but not in the same way - “but to each in relation to his own function”. A wife, for example, has the human differentia (viz. the full rational capacity), but in such a way that “it has no authority (ἄκυρον)”.²⁴ The reason for her being so is not due to any mental or intellectual failure, but rather is linked to her specific functions.²⁵ In Aristotle’s view, it is one’s specific function that decides how one shares or participate in the same human εἶδος as differentia. As a result, though all human beings partake of the same human εἶδος as differentia, there can be as many kinds (εἰδή) of human beings as human functions.

The last piece of evidence I want to bring up appears in Pol. I.8. In that important passage, Aristotle explicitly talks about the “γενή” of human beings:

There are many ways of life (βίοι πολλοὶ) both of animals and human beings … because the same thing is not naturally pleasant to each kind of animal according to nature but different things to different kinds. Among the carnivorous and the herbivorous themselves their ways of life differ from one another. In the ways of life of human beings too there are great differences. The idlest are shepherds. They get their subsistence without trouble from tame animals … others live by hunting, which is of different kinds. Some, for example, live as brigands, others, who dwell near lakes or marshes or rivers or a sea in which there are fish, live as fishermen, and others live by the pursuit of birds or wild beasts. But the most populous division of human being (τὸ δὲ πλεῖστον γένος) live from the land and from cultivated crops. (1256a20-40)

This passage is worth noting for two reasons. Firstly, it shows that human beings can differ from each other with respect to their ways of life (βιοῖ). Secondly, it suggests that the different human ways of life can lead to different divisions (γενή) of human beings, in which “the most populous division (γένος) of human being” is that which lives “from the land and from cultivated crops” (1256a38-40). All this suggests that although Aristotle doesn’t allow human beings to be different in differentia, he does accept that human beings can differ with regard to their ways of life, and such a difference is a cause of division for both animals and human beings.²⁶ On this account, therefore, the human being can be divided into multiple γενή (or εἰδή), including but not limited to, the nomad, the farmer, the brigand, the fisher, and the hunter (1256b1-2).

It should now be obvious that though the human εἶδος as differentia is for Aristotle indivisible, the human εἶδος as function or way of life is not. It can be divided into multiple εἰδή that are manifested in various human functions and human ways of life.

4 Human ΕΙΔΟΣ as two kinds of ENEPΓEIA

By making the distinction between human εἶδος as differentia and human εἶδος as function or way of life, a question naturally arises as to what extent the two kinds of human εἶδος are connected. The connection, I suggest, depends on Aristotle’s thesis that the εἶδος is an (or a kind of) actuality (ἐνέργεια).²⁷ This thesis connects the human εἶδος to the famous Aristotelian distinction between δύναμις and ἐνέργεια, which is the main topic of Aristotle’s Metaphysics Θ and De Anima II.

In Metaphysics Θ, Aristotle makes a distinction between two senses of δύναμις, according to which, δύναμις in the primary sense refers to a capacity to produce a change (κίνησις) (Metaph. 1046a12). A doctor, for example, has the δύναμις to produce a change in the patient so as to bring about health. In another sense, however, δύναμις denotes a potentiality, which is correlated to actuality (ἐνέργεια) (Metaph. 1048a25). A δύναμις, in this sense, refers to a teleological state other than a simple capacity. It can be said, for example, that a housebuilder who is not in the actual state of building is a housebuilder in potentiality (ἐν δυνάμει). In De Anima II, Aristotle makes even further distinctions with respect to the second sense of δύναμις, viz. δύναμις as potentiality. Take a house for example. A house, according to Aristotle, can be either of those:

1. bricks and stones;

2. a covering consisting of bricks and stones laid thus and thus;

3. a covering that consists of bricks and stones laid thus and thus and in which people live;

A house in sense (a) is a house in its first potentiality. It is just some matter (ὕλη) with a mere potential to be disposed in the way a house is supposed to be. A house in sense (b) is a house in its first actuality. It has been actually disposed in such a manner that it consists of both the matter (viz. “bricks and stones”) and the form (viz. “the juxtaposition”) of a house. It is now no longer any chance aggregation of bricks and stones, any sheer material potentiality, but the πρώτη ἐνέργεια, the first actuality of those bricks and stones qua matter. But the house as the first actuality of the bricks and stones is still, strictly speaking, not actually a house. For the essence of a house is the actuality of a house qua house, which might be termed as “home”. In this sense, the house in sense (b) still involves potentiality: it is actually a house, but that actuality remains in the meantime a potentiality to perform the function of a house qua house. Only the house in sense (c) - the house in its second actuality - can be called a house without qualification for Aristotle. For it is the only house that is actually functioning as a house qua house.

Now how does this distinction contribute to our understanding of human εἶδος? My suggestion is as follows: when Aristotle is using the human εἶδος in the sense of the ultimate differentia for human being, the human rational capacity, he not only understands it as a capacity, but also as a potentiality or, more specifically, as a second potentiality.²⁸ The human being who possesses the rational capacity (viz. the human εἶδος as differentia) is, in Aristotle’s view, both an actual human being and a potential human being: he is an actual human being because he has the actual power to exercise his rational capacity in one way or another; he is a potential human being because though possessing the power, he is not actually exercising it. The real actual human being is for Aristotle not the one who merely possesses the human rational capacity, the human differentia, but the one who has further actualized this capacity qua potentiality, making it a “being-at-functioning” (ἐνέργεια). Such a “being-at-functioning”, in Aristotle’s view, is “living in accord with reason”.²⁹ So, a real actual human being is ultimately the one who leads an active life of that which possesses reason (πρακτική τις τοῦ λόγον ἔχοντος) (NE 1298a2). In this way, the human εἶδος as function or way of life is the second actuality of the human εἶδος as differentia. The relationship between the human εἶδος as differentia and as function or way of life is that between the human εἶδος as first actuality (human εἶδος_A1) and the human εἶδος as second actuality (human εἶδος_A2).

If human εἶδος_A1 is human εἶδος as differentia (διαφορά), and human εἶδος_A2 is human εἶδος as function (ἔργον) or way of life (βίος), one may wonder how is it possible that the same human εἶδος is indivisible in the sense of human εἶδος_A1, but divisible in the sense of human εἶδος_A2? In De Anima 3, in explaining how sense discriminates different objects of the same sense, Aristotle gives a solution:

For the same thing, something indivisible, is potentially (δυνάμει) opposite things, though it is not so in its being, but rather is divided by being-at-functioning (ἐνεργεῖσθαι), and cannot simultaneously be white and black … perception and intellection are something of this sort. Rather, it is like what some call a point: it is both indivisible and divisible, insofar as it is either one or two. Hence, insofar as it is something indivisible, what discriminates is one thing and it discriminates simultaneously, while insofar as it is divisible, it uses the same token simultaneously twice over. Hence, insofar as it uses the same limit twice, and discriminates two separate things, there is a sense in which it discriminates separately; but insofar as it uses one, it discriminates one thing and does so simultaneously. (427a6-14).³⁰

Something indivisible can readily be divided in potentiality, but the problem is whether it can also be divided in actuality. In this passage, Aristotle suggests that it can if one understands such entity (e.g. ἡ αἴσθησις καὶ ἡ νόησις, 427a8-9) as pointlike: lacking extension in magnitude, a point is indivisible. But as the multiple-sided boundary between multiple touching lines, the point is in a way divisible.³¹ If the same account applies to the human εἶδος, the human εἶδος as pointlike can be both indivisible and divisible in actuality:

As the joint point of multiple lines (viz. multiple human functions/ways of life), the point (viz. the human εἶδος) is used as one. But as the boundary of multiple lines (viz. multiple human functions/ways of life), it is also used as multiple. So, while the point (viz. the human εἶδος) is one and the same for all the lines (viz. human functions/ways of life) that meet at it, it is in a way divisible, allowing lines (viz. human functions/ways of life) to be different and distinct from each other. On this account, therefore, the human εἶδος_A1 (viz. the point as the joint point) is indivisible in its being, whereas the human εἶδος_A2 (viz. the point as the boundary of multiple lines) is divisible with respect to different human functions and human ways of life (viz. different lines of intersection).

5 Conclusion

In this paper, I have shown that a substance like human being can be understood both as a composite substance and as a (second) actuality. As a composite substance, it is a compound of matter and form, genos and differentia. In this sense, a human being is a composite of a body and a (rational) soul, and the human εἶδος is the rational soul-capacity, known as the ultimate differentia of human being; as an actuality, however, a substance is the being-at-functioning (ἐνέργεια) of its εἶδος as differentia. A human being, in this sense, is the being-at-functioning (ἐνέργεια) of his rational soul-capacity, which is a “life in accord with reason”. The human εἶδος, in this sense, is the dominant function (ἔργον) or way of life (βίος) of a human being.

The two senses of human εἶδος can help, in my view, to explain why Aristotle can be committed to both SHET and MHET: when Aristotle is committed to the SHET, he is using the human εἶδος in the sense of human differentia. The human εἶδος in this sense is indivisible. But when Aristotle is committed to the MHET, he is using the human εἶδος in the sense of human function/way of life. The human εἶδος in this sense is divisible. I concluded with my own account of how the two senses of human εἶδος can be united in Aristotle’s famous account that εἶδος is (an) actuality (ἐνέργεια). I argued that the two senses of human εἶδος correspond to two kinds of εἶδος as actuality (ἐνέργεια). The relationship between human εἶδος as differentia and human εἶδος as function/way of life is that between human εἶδος_A1 and human εἶδος_A2. Human εἶδος_A1 is one and the same for every human being, but human εἶδος_A2 can be different with respect to different kinds of human functions and human ways of life.

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• 1
  Aristotle has many uses for the expression εἶδος. Since distinguishing those uses is one major task of this paper, I shall leave εἶδος untranslated throughout.
• 2
  See Ward 2008, pp. 75-98; Gallagher 2011, pp. 363-384.
• 3
  Ward’s solution, however, cannot explain why Aristotle claims that human beings, generally speaking, can differ in εἶδος. For all the human male citizens, on Ward’s interpretation, cannot differ with regard to their deliberative capacities.
• 4
  For a list of the meanings of εἶδος, see Studtmann 2008, pp. 1-26. It should be noted that even though Woods 1993, pp. 2-3, challenges the thesis that εἶδος is a homonym for Aristotle, he doesn’t deny that there is a “diversity of ways in which Aristotle uses that term [εἶδος]” (2). Wood’s objection can be best summarized as follows, namely, homonyms need not be unconnected. That is, to say X has the meaning A and the meaning B doesn’t exclude the possibility that the two meanings are connected. For Woods, therefore, the human εἶδος as form and the human εἶδος as species are not necessarily distinct.
• 5
  See Aristotelis opera edidit Academia Regia Borussica, Vol. V, 217b58-219a59. It does not mean, however, that the various senses of εἶδος distinguished here are unrelated (and even opposed to each other). For example, the shape is always implied in the formal cause, and the species/genus is definitely bound up with differentia/essence. The distinction only aims to single out different aspects - the spatial aspect, the taxonomical aspect and the dynamical aspect - of Aristotle’s uses of the term εἶδος for consideration.
• 6
  Unless indicated otherwise, all translations of Greek texts are borrowed from Aristotle 1984, with modifications.
• 7
  See e.g. Pellegrin 1986, p. 110.
• 8
  The Greek text of GA 767b5-7 reads: γὰρ ὁ μὴ ἐοικὼς τοῖς γονεῦσιν ἤδη τρόπον τινὰ τέρας ἐστίν. παρεκβέβηκε γὰρ ἡ φύσις ἐν τούτοις ἐκ τοῦ γένους τρόπον τινά. Traditionally, the phrase ἐν τούτοις has been understood to mean “in those cases that the offspring doesn’t take after his parents”. I suggest, however, that one can take the first τρόπον τινά as an indication of the two types of monstrosities Aristotle has in mind (GA 769b25-26). On this reading, the phrase ἐν τούτοις can be understood to mean “in those cases of the first type of monstrosity” (viz. monstrosity in terms of resemblance).
• 9
  This point becomes even more obvious if one considers the fact that the female is said to be generated as a kind of monstrosity (GA 767b5-14).
• 10
  Cf. PA 640b30ff.
• 11
  Notably, see Balme 1962, pp. 81-98; Pellegrin 1986, pp. 68-69; Lennox 2001, p. 122. For a recent opposite view, see Katayama 2017, pp. 422-428. While it may be right for Katayama to point out that Aristotle can possibly hold, due to his “deep metaphysical and epistemological commitment” (p. 428), the view of fixed species, Aristotle’s practical use of the terms γένος and εἶδος does not live up to this commitment.
• 12
  Indeed, Aristotle has given definitions of human being in various works, but in none of them is the differentia unanimous. Human being is defined, for example, as an animal which is mortal and bipedal in APr. 31, and tame and bipedal in APo. 13. According to PA 1.2-4, an adequate definition must be differentiated simultaneously by all the relevant differentiae that are in the substance. Thus the APr and APo definitions cannot be adequate definitions. For it doesn’t consist of all the relevant differentiae that can mark off the genus of human being from other animals - the combination of differentiae mortality and split-footedness is common to a large variety of animal groups besides human beings. Moreover, differentiae like wildness and tameness are not elements in the substance, but are accidental attributes that will even falsely “divide the εἴδη that are same” (PA 643a35-643b4).
• 13
  There is a consensus among Aristotelian scholars that the PA account of division reflects the corrected Aristotelian theory of division. That is to say, Aristotle has denied the possibility in his later biological writings that the adequate differentia can be attained through a single division. The adequate differentia, on this reading, can only be the combination of all the relevant differentiae (see Balme 1987, pp. 69-89; Falcon 1997, pp. 127-146). If this is true, human rational capacity (λόγος) alone cannot be an adequate differentia that marks off the genus of human being. I doubt, however, that the PA account of division reflects a departure from Aristotle’s early account of division. My suggestion is that the difference between the single differentia theory of division and the multiple differentiae theory of division is only a difference between the definiendums. That is to say, in defining the human being as animal with multiple differentiae (cf. the APr and APo definitions of human being), the definiendum is human being as one animal among many; whereas in defining the human being as animal with a single differentia, viz. reason (cf. the Pol definition of human being), the definiendum is human being as human being. This explains why Aristotle has excluded the discussion of reason in his biological writings (see Lennox 1999, pp. 1-16). For Aristotle’s aim is only to investigate human being as one animal among many. If I am right, the genus of human being, in Aristotle’s view, can be marked off by both a single differentia and multiple differentiae.
• 14
  I modified Shields’ formulation (cf. Shields 2001, p. 146).
• 15
  Scholars have no consensus on what the real target of Aristotle’s criticism is. Waerdt holds, for it is clear that the bipartite division questioned here is also adopted by Aristotle, that the critique contains a self-criticism of Aristotle own practice and is therefore destructive (see Vander Waerdt 1987, p. 632). Corcilius and Gregoric suggest that Aristotle is only against the Platonist criteria for soul division, viz. dividing the soul according to capacities/potentialities (See Corcilius & Gregoric 2010, pp. 107-108). My own reading differs in two aspects. Firstly, I don’t think the text of DA 3.9 consists of a self-criticism of Aristotle’s own soul division. It is true that Aristotle uses his own terminology, τὸ λόγον ἔχον and τὸ ἄλογον, to present the bipartite division of soul, but it cannot be inferred that the bipartite division in question is Aristotle’s own. For the same terminology is also applied to Plato’s bipartite division of soul in Magna Moralia 1182a23-5. Further, I am not convinced that Aristotle’s criticism is simply against the method of dividing according to capacities (κατὰ τὰς δυνάμεις). For Aristotle himself clearly adopts this method in his own practice of soul division. In my view, what Aristotle really objects here is the thought that one can divide κατὰ τὰς δυνάμεις the soul into various concrete parts that possess capacities. This way of understanding helps to explain why Aristotle is able to criticize the Platonist or Academic bipartite and tripartite divisions of soul while maintaining his own, for his soul-divisions are in the first place conceptual.
• 16
  That is, if the number of the soul-parts are equal to that of the soul functions, the soul-parts will be in a way infinite, which is impossible. Moreover, if every part of the soul is divided by a single capacity, it is impossible to explain why some capacity (e.g. the appetitive) seems to be present in different separated parts (DA 432a24-b7).
• 17
  For the distinction between soul and soul part, see Corcilius & Gregoric 2010, pp. 91-92.
• 18
  Only in those beings like gods that the capacity of contemplation is found to exist without any other capacity of the soul. Cf. Metaph. 1072b26-30; NE 1141a34-b2.
• 19
  For Aristotle, there is clearly a distinction between “essential” and “accidental” qualities, see Phys. 226a26-29.
• 20
  There are debates about whether the differentia of substance is itself substance. Aristotle’s remarks in Cat. 5.3a21-22 and Top. 122b15-17 suggests that it is not. The differentia, as those passages show, doesn’t signify the essence of a thing, but rather a quality (e.g. two-footed). On the other hand, however, in e.g. Top. 103b14-16; 153a15-18; 154a26-28, Aristotle seems to embrace the view that the differentia also signifies the essence of a thing. For the view that the differentia of a substance is substance, see Irwin 1988, pp. 64-66; Granger 1984, pp. 1-23. For the opposite, see Morrison 1992, pp. 19-46.
• 21
  Cf. Metaph. I.3.1054b6; NE 8.1.1155b11-15.
• 22
  In the pseudo-Aristotelian Problemata 910a26-37, those who live in warm regions are also said to be wiser (σοφώτεροί) than those who dwell in cold regions. But the difference, as the Aristotelian author explains, is caused either by the temperature of their body or by their age gap. Elsewhere in Metaph. 981a24-982a3 and NE 1177a32-34, Aristotle claims that the philosophers are wiser than the men of experience. But the cause of the difference does not lie in the human εἶδος itself. Rather, philosophers are “wiser” because they use their rational capacity on subject that will enable them to know “the first causes and the principles of things” (Metaph. 982a1-2; Cf. the pseudo Aristotelian Rhetorica ad Alexandrum 1426a10-11: a man … becomes wiser as the result of studying philosophy).
• 23
  One may legitimately raise the question that if the specific function of a human being is determined by both the universal human differentia (viz. the form) and the human body (viz. the matter), how could it, then, still be a form for Aristotle? The answer is that “the ultimate matter and the form are one and the same thing, the one potentially, and the other actually” (Metaph. 1045b18-19), and “when [the matter] exists actually, then it is in its form” (Metaph.1050a16-17). In other words, when the universal human differentia and the human body both exist actually in one particular individual, they exist, according to Aristotle, as one form (εἶδος). The point will definitely become much clearer when I argue in the next section that the human εἶδος as function/way of life is the second actuality of the human εἶδος as differentia.
• 24
  There are controversies around the meaning of ἄκυρον. Some think that Aristotle suggests by this that the deliberative element in the wife cannot rule over her own passions. (Cf. Fortenbaugh 1977, pp. 135-40; see also Lord 2013, Book 1, n.60). Some take this as a reference to a wife’s social subordination to a husband (Cf. Swanson (1992), 56). Some, while maintaining the political dimension in Aristotle’s claim, offer different explanations of why Aristotle thinks that the wife’s deliberation is ἄκυρον. For example, Karbowski 2014, pp. 435-460, argues that “women lack authority over men because their rational faculties are intrinsically deficient”. Sparshott 1983, pp. 1-20, argues that the natural function calls for the wife to play the subordinate role.
• 25
  As we have seen in the previous section, all human beings share the same rational capacity. The reason why the rational capacity in female is not authoritative is due to the defectiveness of female body qua matter.
• 26
  Cf. HA 590a16-17; PA 662a33-b16; 693a11-23.
• 27
  Cf. Metaph. 1043a18-21; 1043a29-35; 1043a37-b2; 1050b2; 1071a8-9.
• 28
  Cf. NE 1170a16ff: “they define living in the case of animals as a capacity for perception, and in the case of human beings as a capacity for perception or thought. But a capacity is traced back to its activity, and what is authoritative resides in the activity. So it seems that living is, in the authoritative sense, perceiving or thinking”.
• 29
  The passage to which I want to call the reader’s attention is Metaph. 1050a5-7: “for example, man is prior to child because the former [the man] already has the form (ἤδη ἔχει τὸ εἶδος), while the latter [the child] doesn’t”. Certainly, the εἶδος here cannot mean the εἶδος as differentia, the rational capacity. For a child also has it (Pol. 1260a13). What the child lacks, according to Aristotle, is “living in accord with reason” (NE 1119b5-6; 13-15; 1174a1-3; MM 1206b22. See also NE 1185a2-4 where Aristotle claims that child cannot attain happiness which is an ἐνέργεια of its human εἶδος) which is the “being-at-functioning” (ἐνέργεια) of its rational capacity qua potentiality. Thus we can understand why Aristotle says the human εἶδος that a child possesses has “not achieved its end” (ἀτελές) (Pol. 1260a14), for the end of human εἶδος is the actuality of human εἶδος as differentia.
• 30
  Here the translation is mine.
• 31
  I have followed the reading of Polansky 2010, pp. 398-400.
• Data availability statement:
  The datasets related to this article will be available upon request to the author.
• *
  This work was supported by National Social Science Fund of China (Grant Number 24CZX071), and the Zhishan Young Scholars Programme of Southeast University (Grant Number 2242025RCB0044).

Edited by

• Editores responsáveis:
  Inácio Helfer
  Leonardo Marques Kussler
  Luís Miguel Rechiki Meirelles

Data availability

The datasets related to this article will be available upon request to the author.

Publication Dates

• Publication in this collection
  22 June 2026
• Date of issue
  2026

History

• Received
  25 Apr 2025
• Accepted
  14 Nov 2025