Plato vs. Aristotle on Justice, Virtue, and the Soul

Introduction: The Challenge to Justice in Plato's Republic

In Book I of Plato's Republic, Thrasymachus, Glaucon, and Adeimantus provide intellectual foils for Socrates's ethical philosophy. Socrates responds to Thrasymachus's stance, which is essentially that "the life of an unjust person is better than that of a just one" (p. 88; 347e). Thrasymachus goes so far as to state that justice is "noble naivete," and therefore not worth pursuing at all (348c). Glaucon immediately takes the side of Thrasymachus by stating that the life of an unjust person is "more profitable," at the very least, than the just life (p. 88, 347e). Agreeing with Glaucon's doctrine of self-interest, Adeimantus offers his perspective in Book II of The Republic. Glaucon's brand of justice holds that good reputation is the most important thing — a person does not want to be just if those just acts go unnoticed or unrecognized. More importantly, Adeimantus states that a person would be better off committing unjust acts and getting away with them, because their reputation would remain intact.

Thrasymachus, Glaucon, and Adeimantus each offer sensible, practical, and material counter-claims to Plato's (Socrates's) central thesis that justice is an end in itself and a goal that also brings about goodness and happiness. Plato meets the intellectual challenge of these three figures in two ways: by referring to the concept of the Forms, and by referring to the concept of the tripartite division of the soul. The tripartite division of the soul has its macrocosmic counterpart in the polis, and therefore an orderly soul is matched by an orderly society. When Aristotle grapples with the validity and value of both virtue and justice, he takes a different approach than Plato does. Aristotle cuts to the heart of the argument by insisting on a distinction between acts that are just and acts that are virtuous. Moreover, Aristotle's ordering of the soul is less rigid than Plato's. Aristotle's argument is more effective for responding to Thrasymachus, Glaucon, and Adeimantus not because he proves his case better, but because he appeals to the logical and ethical framework that those three interlocutors work with — whereas Plato does not.

Plato's Response: Forms, the Soul, and Absolute Justice

Plato is, in modern terms, not on the same wavelength as Thrasymachus, Glaucon, and Adeimantus. The three challengers approach the question from a broadly utilitarian perspective in which there are no moral absolutes. With no absolute ethical truth or values, the ends can easily justify the means. It makes sense, then, that Thrasymachus, Glaucon, and Adeimantus do not find inherent value or worth in either justice or virtue. For Plato, justice and virtue are Forms — inherently and immutably absolute states that must be achieved and attained in order for a human being to experience happiness. Happiness is an end-product, symptom, or by-product of justice.

Plato's vision of an orderly universe, with the Forms as the absolute and right expression of all things, runs contrary to the metaphysical vision that Thrasymachus, Glaucon, and Adeimantus posit, even though their metaphysic is less developed than that of Socrates and Plato. With regard to the argument over the validity of justice, Thrasymachus, Glaucon, and Adeimantus simply point to practical matters that Plato finds too mundane to entertain. All Plato can say in response is that the abstract notion of justice is good and has inherent value — a reply that carries little weight for those committed to a materialist worldview.

Thrasymachus, Glaucon, and Adeimantus: The Materialist Position

Thrasymachus argues that a self-serving act may be unjust, but that type of injustice is ethically permissible because it preempts injustice done to the self. Thrasymachus is actually completely unconcerned with justice as an ideal; he presents ethics as a matter of "what's in it for me?" He is a political realist who sees that justice is not an abstract ideal — or even if it were, its ideal would be untenable for human beings. Thrasymachus finds that those in positions of power who wield the sword of justice are the only ones empowered to determine what acts are deemed just or unjust. For an individual to act in accordance with some abstract Form of justice, in the spirit of doing good or being virtuous, that person is categorically naive, according to Thrasymachus.

Glaucon agrees with Thrasymachus but for different reasons. He is slightly less pessimistic and does not categorically dismiss the Form or reality of justice or virtue. Instead, Glaucon uses the story of Gyges to show that just acts must carry some kind of reward for the person — and that reward is honor, glory, and good reputation. Adeimantus chimes in to agree that most people need and want honor and glory when they act justly. However, he adds that people also want honor and glory even when acting unjustly. All three men believe that justice is valuable only if it brings personal reward, and they measure that reward in terms Plato would consider mundane. Because Plato cannot engage with Adeimantus, Thrasymachus, and Glaucon on their materialistic outlook, his argument is largely lost on them.

Conclusion: Reason, Luck, and the Pursuit of the Good

A well-ordered soul with Reason at the top of the hierarchy is a sufficient condition for happiness, according to Plato. Plato is optimistic in the sense that he believes ethical badness is not possible or does not truly exist, in the same way that the color white is the absence of color, or cold is the absence of warmth. Plato would note that cold doesn't "exist" — only a heat source exists. Therefore, the pursuit of justice is the pursuit of that symbolic Sun to which he refers in the Allegory of the Cave. Aristotle's more flexible account of the soul, his attention to environment, and his willingness to acknowledge the role of luck make his argument far more accessible to the materialist and realist sensibilities of Thrasymachus, Glaucon, and Adeimantus — even if Plato's vision of justice as an absolute Form remains philosophically the more ambitious and, in its own terms, the more complete.