Aristotle’s Politics and Plato’s Republic both posit inherent capabilities that exist in humans by “nature,” which they respectively argue serve as frameworks for achieving political justice and harmony in the polis. Plato’s division of the kallipolis mandates specialization by class and knowledge of the Theory of Forms—exemplified through his Myth of Metals—while Aristotle’s theory of “natural slavery” similarly draws from assumptions of one’s “natural” ability to reason and channel the rational part of one’s soul. In attempting to provide an objective framework for the organization of structure and class, Aristotle particularly delineates the concepts of “nature” and “natural” and his justifications for “natural slavery”: this framework centers on the conception of entities that exist by “nature” and in turn are categorized as “natural” entities, which serve as his justification for “natural slavery.” Plato and Aristotle evidently share similar views in allocating citizens based on inherent, “natural” abilities, but operate on fundamentally different premises: Plato is concerned with spreading uniform virtue in his utopian kallipolis, based on the one just individual, whereas Aristotle poses practical social stratification based on ruler-centered dynamics, social inequalities, and the union of subjects varying in virtue. Yet, Aristotle’s corresponding arguments in Politics—in favor of natural rights—contradict the arguments he presents in Nicomachean Ethics, where he posits that virtue, the ability to rationally choose the “intermediate,” can “come about as a result of habit” (1103a17). While Aristotle’s fundamental arguments concur with Plato’s insistence on natural hierarchy rooted in knowledge and harmony of the tripartite aspects of the soul, Aristotle’s self-contradictory perspectives sway from Plato’s—and his own—conception of natural rights, and thus undermine his arguments in favor of natural unequal hierarchies, lending more credence to Plato’s metaphysical framework.

Aristotle pursues a teleological approach for his categorizations of natural rights, arguing that the “nature” of entities consists of an inherent function (ergon) and end goal (telos) to which they strive towards—accordingly, Aristotle assumes that the “nature” of human beings is to form into political communities and pursue a happy (eudaimonia) and virtuous life, arguing that “a human being is by nature a political animal” governed by telos (1253a). Moreover, from a physiological perspective, for an entity to exist “by nature,” Aristotle posits that it must possess “an internal source of change and staying unchanged, whether in respect of place, growth and decay, or alteration,” (Introduction xlix) as well as a compound of matter and form, which further constitute the essence of its “nature.” This can also be characterized as its canonical nature, which constitutes the essence of an entity’s “nature.” An entity that thus exists by nature can be characterized as a “natural” entity. Aristotle notes that the nature of individuals is the inherent “character it has when its coming-into-being has been completed” (1252b30)—in other words, the innate qualities one possesses.

Notably, Aristotle uses this conception of natural rights to categorize slaves as “property” by highlighting how their physical inclinations augment the soul of the master and contribute to the harmonious balance of “part and whole”—his arguments are predicated on the idea that some people are fit to rule (masters), and some to be ruled (slaves). Central to his later arguments is the notion that were such a dynamic to be dictated by law, as opposed to a natural basis, the mutual benefits and friendship associated with the relationship would also be undermined. Aristotle argues that the souls of slaves differ from that of those who possess the ability to reason, emphasizing that slaves are naturally suited to menial work that does not require reasoning, while free men are naturally inclined towards the rational part of the soul.

To Aristotle, slaves may understand the notion of reasoning, but do not actually possess these abilities—he particularly emphasizes how the rational part of their souls differ from that of free men, thereby highlighting that he sees the union of naturally virtuous and unvirtuous individuals in the polis as essential to political unity. Aristotle argues: “the deliberative part of the soul is entirely missing from a slave; a woman has it but it lacks authority; a child has it but it is incompletely developed” (1260a12). He emphasizes that the rational part is “entirely missing” from a slave’s soul, arguing instead that natural slaves are “people whose task, that is to say, the best thing to come from them, is to use their bodies” (1254b19)—those who are, from a visual perspective, more naturally suited for physical tasks that require the use of “their bodies” as opposed to reasoning. As such, to Aristotle a slave can not be characterized as a human being, but rather property, or an “animate tool.” In extending this characterization to women and children, Aristotle illustrates his overarching view on naturally derived hierarchies in the polis: there exists a “natural superior” and “inferior” between slave and master, between body and mind, between woman and man.

However, if virtue is contingent on rationality and reason, as Aristotle argues in Nicomachean Ethics (”this being determined by reason, and by that reason by which the man of practical wisdom could determine it” (1107a1-2)), then his “natural” stratification assumes that members of the polis “naturally” possess varying levels of virtue, which is seen in their nature. This requires that members like slaves, women, and children, be regarded as unvirtuous in their natural inferiority, further cementing these rigid social structures. This, however, counteracts Aristotle’s objective of promoting virtue in the city, introducing another contradiction and fallacy in his arguments. Moreover, Aristotle seems to suggest now in Politics that virtue, due to reason in the soul, arises naturally—yet in Nicomachean Ethics, he argues the opposite: “none of the moral virtues arises in us by nature, for nothing that exists by nature can form a habit contrary to its nature” (II.1.19-21). If this is the case, then the virtues absent in slaves cannot be formed through habit as Aristotle postulates in Nicomachean Ethics. This would seem to invalidate his theory of natural rights, and lend credence to Plato’s arguments.

Aristotle further argues that hierarchy of slaves and masters is beneficial for both parties by arguing a natural, biological basis of physical fit: “Nature tends to make the bodies of slaves and free people different too, the former strong enough to be used for necessities, the latter useless for that sort of work, but upright in posture and possessing all the other qualities needed for political life” (1255a25). Aristotle highlights a natural physiological basis for the master-slave dynamic, further highlighting how the rational and physical parts coalesce to form a just and beneficial relationship. Aristotle particularly argues that the slave and master coalesce into a just “whole,” synthesizing the “body and soul” (1255b5). By considering those who may not be slaves by nature, but by law, Aristotle argues that the law would undermine the mutually beneficial relationship between slaves and masters, founded on friendship, and as such hurt both parties. Plato’s Myth of Metals in Republic acts as the counterpart to Aristotle’s natural hierarchy in Politics, where both theories share in the fundamental premise of humans being endowed with natural abilities suited towards different roles in society, whose influence is seen in Aristotle’s arguments—both seek political unity and harmony of the different parts of the polis, but Plato’s seeking of uniform virtue in his ideal state causes disagreement with Aristotle’s theories of stratification. Plato explains his theory of specialization in the kallipolis, where subjects are, by nature, suited for specific roles in the hierarchy: “we aren’t all born alike, but each us differs somewhat in nature from the others, one being suited to one task, another to another” (370a). Inherently, both thinkers teleologically stratify their citizens in pursuit of political unity in the polis. When Plato presents the Myth of Metals, however, he notes that “‘all of you in the city are brothers’,” (415a) homogenous in virtue in that sense. In the Myth of Metals, God endows certain groups of people with different metals, naturally allocating those suited to rule, or act as guardians or craftsmen in the polis. Aristotle’s theory on natural slavery coincides with this perspective of people being naturally suited for roles in the polis.

However, Plato proposes a communist approach for unifying the city, and operates in an ideal state, where everyone is just and as uniform in virtue as possible; Aristotle, as shown earlier, seems to seek both virtuous and unvirtuous individuals in his polis. Taken in tandem, Aristotle’s conception of natural rights differs from that of Plato in their respective placements of virtue in the polis. Moreover, the Myth of Metals further exemplifies Plato’s view that these natural placements by God determine one’s role in society, precluding the fostering of virtue and reason through education that Aristotle puts forth in Politics. Yet, Aristotle’s self-contradicting arguments with the fostering of virtue, stemming from his theory of natural slavery, seems to inhibit our ability to make these comparisons.

Aristotle’s theory on natural slavery, which seems to imply the natural endowment of virtue and vice in individuals, is evidently weakened by contradictions between arguments he makes in Nicomachean Ethics. Plato’s influence on Aristotle’s conception of natural rights is evident, however—additionally, Aristotle’s argument for rigid social structures coincides with the hierarchy articulated by Plato. Aristotle’s ideas, however, diverge in the natural assignment of virtue to individuals in the polis, and it seems that the contradictions in his theory further prevent an apt comparison of his views with that of Plato’s. As such, it seems favorable to concur with Plato’s abstraction of natural rights and virtue in Republic, in light of Aristotle’s flawed attempt to argue the premise of natural slavery.

Works Cited:

Reeve, C. D. C. (1998). Aristotle: Politics. Hackett Publishing Co.

Ross, David. (2009). Aristotle: The Nicomachean Ethics. Oxford University Press.

Grube, G. M. A. (1992). Plato Republic. Hackett Publishing Co.