Regulating the human genes in antiquity: Plato’s and Aristotle’s Eugenics

Written by Triet Nguyen


1§1 Ancient medicine involves not only the study of diseases and their treatments but also eugenics, attempts to artificially regulate and better the human gene pool. Although the term eugenics was not coined until 1883, the concept had been conceived by the ancient Greek philosophers Plato and Aristotle millennia ago. Plato and Aristotle develop their theoretical eugenic schemes based on their interpretations of the Hippocratic theory of heredity. As their concepts of heredity are both different and alike, similarities and distinctions in their eugenic schemes emerge. In this paper, by examining the Aristotelian and Platonic views on heredity, I will analyze how exactly their concepts of heredity give rise to similarities and differences between their eugenic ideas. First, Aristotle and Plato both agree on the inheritance of acquired characteristics and support infanticide and child exposure as means to eliminate undesirable traits in children of deformed parents. Nonetheless, due to subtle dissimilarities between their concepts of heredity, their implementation of the practice differs. Finally, I will look at how Aristotle’s biological and Plato’s social theories of heredity lead their eugenic ideas to two completely separate directions. While Aristotle demands the provision of care for expectant mothers to improve the quality of genetic materials, Plato calls for the establishment of a state-level system of marriage arrangement for the proactive regulation of the human gene pool.

The Hippocratic theory of heredity

2§1 The Hippocratic concept of heredity, pangenesis, states that genetic materials derive from all parts of the body and are concentrated in the semen, which then generates all body parts and grows into a human within the womb. Acquired physical traits are passed down from one generation to the next in the process (Zirkle 1935:430–431). This theory is best exemplified in the Hippocratic treatise On the Sacred Disease where the heredity of the sacred disease is explained.  According to Hippocrates, the origin of this disease is ‘hereditary, like that of other diseases’ (On the sacred disease 5). Because seeds, or semen, originate from all body parts, they will share the parts’ humoral composition. If there is an imbalance of humors in an organ, seeds originating from that organ will also suffer from that imbalance. In other words, from ‘the healthy parts’ comes ‘healthy semen,’ and ‘from the diseased parts’ comes diseased semen (Hippocrates On the sacred disease 5). Consequently, diseases as well as physical deformities, are thought to be passed down from parents to offspring. For example, a phlegmatic will give birth to a phlegmatic, a bilious a bilious, and a phthisical a phthisical (Hippocrates On the sacred disease 5).

Physical fitness in Plato’s and Aristotle’s eugenics

3§1 This concept of inheritance of characteristics provides the critical foundation for Plato’s and Aristotle’s eugenic efforts to identify and eliminate negative traits. Both Plato and Aristotle entertain the idea that all parental characteristics, including undesirable attributes such as physical deformities or diseases, can be passed down to the offspring (Zirkle 1935:422). For instance, in History of Animals, Aristotle corroborates the inheritance of various physical deformities with his observations that ‘from deformed parents come deformed children, lame from lame and blind from blind’ (VIII: 6). Since the offspring of these couples would inevitably inherit parental inferior traits such as lameness and blindness, they would not only be of no benefit to society but also encumber it. As a result, the philosophers propose abortion and child exposure as a means to eliminate children of inferior couples in an effort to prevent undesirable traits from propagating, thereby improving the gene pool of the general population. For example, in Politics, Aristotle states that there should be a law against ‘nourishing those that are deformed’ (VII). In other words, inferior children should not be allowed to live.

3§2 Likewise, Plato advocates the riddance of children of inferior parents. As Plato writes in The Republic, weak parents should not procreate (407d). Because their children would inherit their inferior qualities, they would have no strength to lead a meaningful life, or in any way contribute to the state. Moreover, extending medical treatment to these children or their parents would do ‘no good either for the patients themselves or for the state’ (Plato The Republic 407d). Even if the children show no signs of deformity, they should still be exposed for they are ruined and thus, socially unassimilable. Therefore, they must be deprived of all upbringing, education, and physical sustenance, or ‘concealed’, a euphemism for infanticide (Galton 264; Rankin 1965:410).

3§3 Another similarity between the Platonic and Aristotelian eugenics is the use of physicality as the major criterion to decide the fate of a child. For the philosophers, physical and intellectual abilities develop simultaneously. In other words, physicality is critical as ‘the soul depends on the body and matter conditions the mind.’ (Roper 1913:48) Consequently, much of Plato’s and Aristotle’s writings on infanticide discuss the stringent assessment of not just the child’s physique but also its parents. Because physical inferiority implied both a feeble constitution and mind which could be passed onto future generations, should the child be either of weak constitution or born to weak parents, it must be exposed.

Plato’s eugenics considers also mental traits

4§1 At the same time, unlike Aristotle whose heredity considers only the inheritance of physical traits, Plato contemplates the impact of the parents’ immortal soul. For Plato, offspring are fashioned by immortal souls attached to the matter of brain and marrow. In other words, the child inherits parents’ mental characters as well (Preus 1977:70). This belief motivates Plato to incorporate the elimination of dangerous mental traits to his eugenics. For the mentally deprived carries with him ‘a pedigree of congenital ailment’, ‘there was no place in the Platonic Republic for the “unkempt” man’ (Roper 1913:45). Plato demands the segregation of those morally deprived from society for they present ‘no mere encumbrance to society, but an active force of evil’ (Roper 1913:45). Furthermore, Plato dictates that ‘his growth must be stopped’ and that society ‘put him out of the way’ for fear of the spread of moral degeneracy (Roper 1913:45). Toward the end of his career, in Laws, Plato’s conviction in the elimination of moral depravity remains implicit. For instance, he insists that the “madman” and the “beggar”, whom he considers mentally impaired creatures, must be completely segregated and “purged” from the state (Laws 934c, 936c).

Aristotle’s emphasis on infanticide

5§1 The second difference is Aristotle’s eugenics exclusively focuses on the destruction of inferior offspring. It arises from his concern with overpopulation and its economic impact, to which Aristotle attaches great importance. As a result, he demands that ‘a numerical limit must be set upon procreation.’ (Politics VII) Consequently, his eugenic scheme focuses on exposing children of inferior parents by means of abortion and child exposure without any consideration of latent capacity whatsoever (Roper 1913:16). In addition, Aristotle is worried that overpopulation of the lower classes, whom he believes to be carriers of inferior traits, might incite the rise of poverty, crime, and rebellion (Galton 265). This concern cements Aristotle’s emphasis on infanticide.

5§2 Another reason why Aristotle focuses solely on infanticide and child exposure is his serious intention on materializing his eugenic program (Roper 1913:68). Aristotle designs his eugenics to be an applicable social reform, not some tenuous, impractical thought experiment. Therefore, the program has to be founded on widely accepted cultural norms for it to be welcomed by the general public. One cultural aspect Aristotle relies on is ancient Greeks’ approval of the practice of child exposure. In Sparta, for example, the fate of the infant lies in the hand of the tribal Elders. The Elders, after judging its physicality and military potential, or lack thereof, decides whether it could live or be ‘cast into the fateful chasm on the slopes of Mount Taygetus’ (Roper 1913:15). Additionally, it is acceptable for parents to expose children on the grounds of economic constraint in ancient Greece (Galton 265). Given Athenians’ widespread acceptance of the custom, Aristotle believes that his infanticide-heavy eugenic scheme should be practicable in Athens.

Unique aspects of Plato’s and Aristotle’s eugenics

6§1 Similarities and differences between Plato’s and Aristotle’s implementation of infanticide aside, each philosopher’s unique theory of heredity also inspires them to take their eugenic schemes along different trajectories.

Prenatal healthcare in Aristotle’s eugenics

7§1 One unique aspect of Aristotle’s eugenic scheme is his concern with the healthcare provided to the expectant mother. This derives from his rejection of the portion of the Hippocratic pangenesis which claims that genetic substances come from all body parts, concentrate in the semen, and develop into the child in the womb. He argues that it is pneuma or air that is the actual carrier of genetic materials. Semen and wombs are pneuma vesicles that provide the necessary heat, motion, and substrate for the pneuma, which originates from both male and female, to confer human forms onto the womb (Preus 1977:71). Moreover, Aristotle claims that blood comes from food and pneuma, in turn, derives from excess blood (Preus 1977:71). With this in mind, Aristotle insists that intensive care be given to expectant mothers to enhance the pneuma the child will inherit. Mothers should also be advised to exercise, worship the gods of matrimony, and be given nutritional food (Galton 265).

Genetic filtering through selective marriages and education in Plato’s eugenics

8§1 With respect to Plato’s eugenic scheme, it is unique in that besides elimination of undesirable traits, it also aims at promoting the reproduction of superior qualities over inferior ones. For Plato, this could be achieved by regulating reproduction via selective marriage arrangements and education.

8§2 First, the idea of selective reproduction perhaps stems from Plato’s concept of social stratification based on genetics. Plato holds that society consists of three different classes, the rulers, the guardians, and the craftsmen (Brumbaugh 1954:192). Members of each class possess similar genetic composition unique to the class they come from. With regard to genetic quality, the rulers would possess the highest genetic quality, whereas craftsmen the lowest. Plato even conceives the Myth of Metals to convince ancient Greeks that the nature of their reproductive materials determines their social class. According to this myth, the Gods mix different metals into the soul of each individual: gold for the rulers, silver for the guardians, and copper for the craftsmen (Brumbaugh 1954:192). Because children inherit their metal from parents, cross-class marriages could give rise to unexpected metal combinations which potentially attenuate the superiority of a parent’s traits. For example, when the gold from a ruler mixes with the copper from a craftsman, the superior qualities of the gold will be undermined by the copper. Consequently, children of this union will be inferior to those born to parents both from the ruling class. With this theory in mind, Plato insists that class purity, especially among the ruler class, be maintained so that superior traits could be continuously produced and inferior traits reliably regulated. He also fears that indiscriminate mating across social classes would lead to the deterioration of human genetics and eventually, destruction of the state. In The Republic, Plato likens this to selective breeding of stock: without careful breeding, the animals would ‘greatly degenerate’, and this principle ‘holds also for mankind’ (459–461).

8§3 To avert such a catastrophe, Plato urges that society arrange for judicious mating to selectively promote superior qualities and prevent inferior ones from attenuating them. In The Republic, Plato formulates marriage festivals and rigged lottery systems which would simultaneously favor the mating between individuals with high fitness that belong to the same classes, and minimize the probability of a cross-class union (Galton 1998:266). Nonetheless, Plato is also aware that sometimes parents of the same metal composition can produce children of a different metal. Contemplating all possible combinations across the social classes, Plato decides that the union between a ruler and a soldier will produce offspring most capable of protecting and leading the state, and encourages competitive marriages between naturally talented citizens regardless of class (Brumbaugh 1954:193). In so doing, the state could not only promote the proliferation of superior traits but also minimize the propagation of inferior traits and prevent them from undermining superior ones through cross-class procreation. At the same time, however, Plato acknowledges that even with such a system, he still could not absolutely control the human gene pool. This prompts him to propose a second filter using education. Offspring of both the guardian and ruler classes are carefully observed during their education and based on the qualities they display, the children can be demoted or promoted from their current class. For example, if a guardian child displays capabilities beyond its class, it will be promoted to the ruling class. On the other hand, inferior guardian and ruler children will be relegated to the lower classes (Galton 1998:264).

8§4 However, at the end of his career, Plato apparently realizes that the extremity of his system renders itself inapplicable in any meaningful ways. Consequently, in Laws, Plato recommends more moderate legislation for “monogamous marriages with strict chastity outside of it” (Galton 1998:265). In addition, the man is encouraged to wed the woman whose fitness would benefit the city regardless of his feelings towards her, and the origin of the bride and family should be carefully investigated (Galton 1998:265). Again, the purpose of this legislation is to protect class purity. Although the system is less extreme, it still represents Plato’s insistence on preventing the dilution of superior traits and the propagation of inferiority.


9§1 In conclusion, both Plato and Aristotle acknowledge the importance of heredity and believe in the possibility of improving human health with eugenics. Aristotle’s and Plato’s similar, yet dissimilar concepts of heredity provide the conceptual framework that shapes their eugenic ideas.


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Preus, A. 1977. “Galen’s criticism of Aristotle’s Conception Theory.” Journal of the History of Biology, 10(1):65–85.

Rankin, H. D. 1965. “Plato’s Eugenic ΕΥΦΗΜΙΑ and ΑΠΟΘΕΣΙΣ in Republic, Book V.” Hermes 93(4):407–420.

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Zirkle, C. 1935. “The inheritance of acquired characters and the provisional hypothesis of pangenesis.” The American Naturalist 69(724):417–445.

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