Plato’s metaphysical framework for modelling human nature and the city-state in Republic marks the beginning of a series of philosophical thought-experiments and intellectual inquiries intended to explicate the nature of justice, the purpose and role of a leader, and the fundamental ways in which a city-state should operate to promote prosperity and harmony in a society. Fundamentally, these problems are crucial for us—as humans who presumably seek an objective framework for organizing society and government, and determining to what end these institutions be established. Alfred North Whitehead suggests that all European thought is indebted to Plato’s initial ideas—surely there are exceptions to Whitehead’s generalization to all European philosophers, particularly radical thinkers. However, within the scope of metaphysics, ethics, and politics, Plato’s influence on the ideas of later, more popular European thinkers such as Hobbes, Locke, Descartes, and Rousseau is undeniable—namely in the (1) actual problems these thinkers seek to answer and the (2) nature of questioning these philosophical problems and arguments employed to address them. Inherently, these thinkers build from the foundations set forth by Plato—some thinkers explicitly mention Plato in their writings; others, perhaps unknowingly, implicitly evoke Platonic sentiments in their arguments.

As such, later influential European thinkers derive from Plato’s foundations by extracting the strengths and insufficiencies of Plato’s metaphysical framework, assimilating Plato’s use of metaphors and abstractions into a more practical framework for formulating politics in complex societies—for Hobbes and Descartes, particularly, Plato’s influence in two different mediums of philosophical thought is evident: from a political perspective, Hobbes uses Plato’s philosopher-king to highlight the impracticability of Plato’s framework and promote his own agenda; from a metaphysical perspective, Hobbes and Descartes both employ Plato’s Allegory of the Cave to promote a more applicative framework surrounding reason, knowledge, and the pursuit of truth in science. Despite attempting to distance themselves from Plato’s arguments, at their core, both thinkers harness Plato’s teachings as their ideological foundations, and are indeed indebted to Plato—Hobbes and Descartes, perhaps unknowingly, invoke Platonic sentiments in their arguments pertaining to knowledge and reason, further highlighting the extent of Plato’s influence. Thus, within the context of metaphysics and politics, Whitehead makes a valid argument: Plato’s strong influence in the texts of later thinkers is evident and undeniable—Plato inherently speaks through these thinkers, being the foremost philosopher who laid the essential foundations for Western philosophy.

At a high-level, Plato’s contributions center on being one of the first thinkers to propose ideas on the nature of fundamental topics in metaphysics, morality, ethics, and politics. Significantly, in Republic, Plato creates an ideal city-state of uniform virtue and justness, structured hierarchically based on his tripartite soul—he is primarily concerned with spreading uniform virtue in his utopian kallipolis. Plato’s ideal city mirrors the ideal, equanimous mind, which harmonizes its appetitive, spirited, and rational parts. In delineating the nature of a just citizen and his ideal ruler (the philosopher-king), Plato pursues a metaphysical framework rooted in his Theory of Forms, which posits that only philosophers truly possess the innate ability to perceive and understand the abstract Forms—such as Good, Beauty, and Justice—and are suited to be rule a city-state.

Moreover, Plato’s Allegory of the Cave presents a metaphorical framework for furthering his arguments: the cave, for example, is a testament to the way in which Plato’s philosophers venture intellectually beyond the ignorance of the shadowed caves and achieve knowledge of the Forms—metaphorically ascending from the cave towards the outside world illuminated by the sun. Key to Plato’s allegory is his presumption regarding the fallibility of one’s senses—whether that be through the visual or auditory mediums. Plato suggests that there is an objective truth, and the ascension towards that greater truth requires questioning one’s assumptions and acknowledging the fallacies that may cloud our judgement. Descartes and Hobbes both draw from Plato’s metaphysical and mythical framework by meshing aspects of his arguments to formulate ideas that are grounded in science and can be tangibly incorporated in society.

From a political perspective, Plato’s influence on Hobbes’ Leviathan is evident, particularly in Hobbes’ discussion of the nature and education of the sovereign: Plato’s philosopher-king, specifically, is both a point of contention and agreement with Hobbes, who repudiates the general feasibility of Plato’s ideal city-state by criticizing the breadth of knowledge required by Plato’s philosopher-king—Hobbes, however, simplifies Plato’s expansive moral philosophy into an educative framework centered solely on the conception of justice, assimilating Plato’s ideas into a more applicable framework that can be put into practice in his envisioned commonwealth. Hobbes, as such, is indebted to Plato’s original framework in formulating his applicative framework. Hobbes explicitly invokes Plato’s conception of the philosopher-king, concurring with Plato that a sovereign should have knowledge analogous to that of the Forms, but simultaneously asserting the dominance of his more practical framework centered on knowledge of the science of justice, urging for Plato’s “speculation” to be converted into the “utility of practice”:

“And how much depth of moral philosophy is required in them that have the administration of the sovereign power; I am at the point of believing this my labor as useless as the commonwealth of Plato; For he also is of opinion that it is impossible for the disorders of state, and change of governments by civil war, ever to be taken away, till sovereigns be philosophers. But when I consider again, that the science of natural justice is the only science necessary for sovereigns and their principal ministers; and that they need not be charged with the sciences mathematical (as by Plato they are) further than by good laws to encourage men to the study of them; and that neither Plato, nor any other philosopher hitherto, has put into order and sufficiently or probably proved all the theorems of moral doctrines, that men may learn thereby both how to govern and how to obey; I recover some hope that…this writing of mine…convert this truth of speculation into the utility of practice” (XXXI.41).

Key to note in the ending is that Hobbes is foremost concerned with the “utility of practice”—applying political science frameworks tangibly into society, which signifies his break from Plato’s metaphysical framework rooted in abstraction and idealism. Significantly, however, Hobbes agrees with Plato that to resolve disorder in society, the ideal sovereign should be a philosophic ruler of some sort with superior knowledge—one who can also exercise sovereignty “without the help of any interested or envious interpreter” (XXXI.41). Evidently, Hobbes directly draws from Plato’s conception of the philosopher-king, arguing that his own sovereign similarly must have a grasp of justice—except, Hobbes posits that his sovereign need only be versed in the “science of natural justice,” as opposed to the expansive, “depth of moral philosophy” that Plato requires in his philosopher-king, which encompasses knowledge of the Theory of Forms.

At the core of this contention is the general impracticable nature of Plato’s abstract framework that Hobbes perceives: he pinpoints Plato’s philosopher-king as a testament to the unduly amount of knowledge that Plato requires his sovereign to have, emphasizing the inapplicability of Plato’s idealistic philosophic ruler—and ultimately his entire city-state. Hobbes seems to argue in this passage that such a requirement is simply unnecessary, when he believes that knowledge of justice is solely required to make just laws—Hobbes ardently emphasizes the gravity of Plato’s idealism, insisting that “neither Plato, nor any other philosopher hitherto” has provided a sufficient and coherent framework for moral philosophy in general. As such, if Plato and other philosophers have not proved or delineated all possible moral theorems, which we assume to be analogous to Plato’s Theory of Forms, then Plato’s insistence on the philosophic ruler understanding the breadth of moral philosophy corresponding to the Forms, along with the mathematical sciences, is invalid.

Ultimately, Hobbes highlights the impossibility and impracticability of Plato’s idealistic city-state, stemming from his ideal philosophic ruler. Hobbes, like Plato, seeks a philosophic ruler to govern justly, but he disagrees fundamentally with Plato on how educating, creating, and nurturing this ruler in society should be implemented—in other words, Hobbes and Plato agree on high-level foundations for governing structures and rulers in society, but differ on how to apply these principles in practice at a low-level. Hobbes, however, still uses Plato’s ideas to formulate his own arguments by incorporating aspects of Plato’s theories. Plato pursues an idealistic metaphysical framework, whereas Hobbes distinctly notes that his framework is grounded in reality, albeit marginally altered from Plato’s in the context of the philosophic ruler—where Hobbes notes that knowledge of justice is only required as opposed to all knowledge of the Forms. Plato’s ideas, as such, form the groundwork for Hobbes’ ideas. Interestingly, in his overt criticism of Plato, Hobbes seems to exaggerate his distance from Plato’s views—yet Hobbes evidently invokes Plato’s ideas in his arguments on the philosopher-king. And despite asserting the dominance of his ideas over Plato, Hobbes is in fact indebted to Plato for his conception of the philosopher-king, and his criticism of Plato in light of this clear influence further highlights the true breadth of Plato’s influence on the arguments presented in Leviathan.

Furthermore, Hobbes’ use of the terms “science of natural justice” directly counters Plato’s metaphysical conception of knowledge of the abstract Forms of Good and Justice—serving as a testament to Hobbes’ attempt to ground Plato’s abstraction of Justice into a tangible, methodical science that can be understood and applied in practice. In essence, Hobbes pursues an applicable framework that builds off Plato’s abstract framework—Plato’s conception of the Forms, thus, additionally forms the basis for Hobbes’ arguments on the nature of knowledge that a philosophic ruler should possess. Despite Hobbes’ profuse repudiation of Plato’s ideas in this passage, Plato’s strong undercurrent in Hobbes’ ideas is evident—Hobbes’ ideas for the ruler derive from Plato’s philosophic ruler with slight modifications, and the nature of scientific knowledge that Hobbes argues is necessary for his sovereign is a direct response to Plato’s abstract conception of the Forms. From a metaphysical perspective, Hobbes moreover unknowingly invokes Plato’s rhetoric in later sections of Leviathan, essentially embedding Plato’s cave in a religious context using similar imagery of darkness and light. The fourth part of Leviathan is entitled “Of the Kingdom of Darkness,” which describes “spiritual darkness” that results from the promulgation of false and erroneous religious doctrines. Hobbes’ “Kingdom of Darkness” is analogous to Plato’s cave encompassed in darkness, transplanted into a religious context. Hobbes describes this religious cave of darkness as: “a confederacy of deceivers, that to obtain dominion over men in this present world, endeavor by dark and erroneous doctrines to extinguish in them the light both of nature and of the Gospel” (XLIV.1). Hobbes, evidently, employs Plato’s metaphorical conception of the cave to create an analogous cave that deliberately threatens religion in his commonwealth—his likening of light to “nature” and the “Gospel” is analogous to Plato’s conception of truth in his world. Plato evidently speaks through Hobbes, who employs Plato’s mythical and metaphorical methods of modelling his city-state to illustrate the danger of religious depravity in his commonwealth. Hobbes, as such, is indebted to Plato for conceiving this metaphorical model of religion, based on Plato’s original cave.

Regarding Descartes’ metaphysics, Descartes’ arguments in Discourse on Method, which focus predominantly on the pursuit of knowledge, reason, truth in science, and the nature of existing, further invoke Platonic sentiments from the Allegory of the Cave—particularly in the acknowledgment that one’s senses are fallible and reason is the instrument through which humans can achieve truth in science. In effect, Descartes constructs his arguments by using Plato’s allegory to advance a framework for pursuing truth based fundamentally in doubting the world around us—significantly, Descartes aims to create a widespread framework beyond “speculative philosophy” that can enable humans to take control of the natural world, and uses Plato’s ideas in this pursuit. Descartes delineates in Part 6 of Discourse on Method his ultimate aim in pursuing truth in science—namely of setting the foundation for humans to harness the world in a useful and versatile way, particularly in medicine and technology:

“For these notions have made me see that it is possible to attain knowledge which is very useful in life, and that unlike the speculative philosophy that is taught in the schools, it can be turned into a practice by which, knowing the power and action of fire, water, air, stars, the heavens, and all the other bodies that are around us as distinctly as we know the different trades of our craftsmen, we could put them to all the uses for which they are suited and thus make ourselves as it were the masters and possessors of nature” (VI.59-68).

Like Hobbes, Descartes references a “speculative philosophy” that most likely refers, in part, to the philosophy of Plato, whose metaphysical arguments are echoed in Descartes’ rhetoric throughout Discourse. Importantly, Descartes delineates his objective of creating a framework for applying truth that can be applied in society, such that humans can be the “masters and possessors of nature”—with the strongest implication being in advancing technology and medicine, which are fields that seem to intrigue Descartes the most. In pursuit of this objective, Descartes employs Plato’s metaphysical framework for deriving a method by which greater truths can be realized in the world. In creating his framework for deriving truth, Descartes uses Plato’s observations in the allegory to form the basis of his doubtful assumptions of preconceived truths, which derives from initially doubting one’s senses—the Platonic undercurrent in his rhetoric is evidence of Plato’s influence, as well as the fundamental basis the allegory forms for Descartes’ proposal of doubting one’s senses and in turn assuming all truths to be false. He first asserts in Part IV that “senses sometimes deceive us,” hence nothing should be taken to be truth at face-value—Descartes notes that “for although we see the sun very clearly, we should not on that account judge that it is only as large as we see it” (IV.40), nothing that vision as an example of a sensory medium is evidently fallible. This observation is reminiscent of Plato’s allegory, rooted in false assumptions of the world stemming from false visually perceptions of the shadows in the cave. He expands this sensory fallibility to logical reasoning, asserting that fallacies exist in logical proofs and that he must thus assume that all reasoning he has been exposed to is dubious and false. In the process of doubting all notions of truth and reality, Descartes arrives at an “incontrovertible” truth that his thinking signifies his own existence (cogito ergo sum). He thus creates a framework for arriving at this indisputable truth, which begins by considering that all prior assumptions and truths are false, rooted in Plato’s original assumptions—this beginning stems from doubting his own senses, which has a strong Platonic undercurrent, particularly influenced by the Allegory of the Cave. Descartes, importantly, uses Plato’s existing framework to formulate his own applicative framework focused on deriving “incontrovertible” truths from scratch, doubting all preconceived assumptions or notions—his focus on doubting prior assumptions believed to be true stems from his perceived fallibility of one’s senses, which harkens back to Plato’s Allegory, and echoes Plato’s rhetoric. After presenting his proof of God and the soul, which originates from his assumption that he must doubt everything that has been presented to him, Descartes asserts, in a Platonic manner: “But what convinces many people that there is a problem in knowing Him and even of knowing what their soul is, is that they never raise their mind above the realm of sensory things and are so used not to think of anything except by imagining it, which is a mode of thinking peculiar to material objects, that everything which seems unimaginable seems to them unintelligible” (IV.37). Descartes’ emphasis on “raising” one’s “mind above” the senses directly mirrors the ascension towards truth from the underground cave in Plato’s allegory, where the prisoners’ conception of truth in the cave is dependent solely on their sensory perception of shadows until they rise from the cave towards the sun.

Descartes further builds off Plato’s allegory, morphing sensory perception into imagination, suggesting that Plato’s prisoners are incapable of perceiving truth because they are accustomed to only imagining objects they have perceived through the senses—which as Descartes as explained, through Plato, is a fallible assumption, and prevents the realization of greater, perhaps more obscure, truths in the world. As shown, Plato speaks through Descartes in this passage, perhaps unknowingly, and his initial allegory forms the basis for Descartes’ assumption of doubting everything in the pursuit of truth—Descartes takes Plato’s arguments and applies that in his metaphysical framework for pursuing truth in science. He further expands Plato’s argument to conceive of fallible imagination and its impediments to the pursuit of truth—while never explicitly mentioning Plato in his arguments, Plato’s influence as the basis for Descartes’ arguments is evident. Interestingly, like Hobbes, Descartes seems to revel in the dominance of his theory of doubt and journey towards truth—yet his ideas are ultimately and evidently founded on the groundwork laid by Plato. Descartes, as such, is evidently indebted to Plato for formulating his applicative framework for deriving truth in the world.

The pertinence of the fundamental problems first posed by Plato is reflected in the breadth of arguments put forth by later, influential European thinkers—particularly Hobbes, Descartes, Locke, and Rousseau—whose commentaries both converge with and diverge from Plato’s original framework. They all seek to answer the same fundamental questions Plato initially poses—how best to organize government, establish sovereigns or ruling bodies, and characterize the natural state of humans, within and outside society. Some of the most influential European writers, such as Hobbes and Descartes, explicitly reference Plato in their arguments, while implicitly responding to or echoing remnants of Plato’s own writings. The nature of this connection stems, arguably, from both the perceived strengths and insufficiencies of Plato’s idealistic metaphysical framework, and the need to tangibly apply Plato’s abstract principles in more complex societies relevant to the time periods of later thinkers. Hobbes and Descartes evidently echo Plato’s rhetoric and ideas in their arguments—despite either separating themselves from Plato or asserting the dominance of their own theories, Plato evidently speaks through both thinkers, ultimately highlighting the breadth of his ideological influence across the metaphysical and political spectrums of study. These thinkers, as such, are indebted to Plato’s original frameworks in creating their own practical frameworks for application in society.

Works Cited

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

Johnston, David, and Kinch Hoekstra. (2021). Hobbes Leviathan. The Norton Library.

Mclean, Ian. (2006). Rene Descartes: A Discourse on Method. Oxford University Press.