Plato's Republic and Aristotle's Nicomachean Ethics

Syllabus. PHI 420: Topics in Philosophy

Instructor: Thomas A. Blackson
Pre-requisites: PHI 328 (History of Ancient Philosophy) or its equivalent is helpful but not required

Some Online Resources:

Perseus Digital Library:
Plato, Republic
Aristotle, Nicomachean Ethics

Loeb Classical Library:
Plato, Republic

Plato. Republic. (Translated from the New Standard Greek Text, with Introduction, by C. D. C. Reeve). Hackett Publishing, 2004.

Stanford Encyclopedia of Philosophy:
Plato's Ethics: An Overview
Plato's Ethics and Politics in The Republic
Aristotle's Ethics

History of Philosophy Without Any Gaps
This course is a study of Plato's Republic and Aristotle's Nicomachean Ethics.

In the Republic, the subject is justice. Socrates explains what justice is in a "city" (πόλις) and in a human being, and he argues that the just life is better than the unjust life.

In the Nicomachean Ethics, the subject is the good life. Aristotle tries to clarify, supply detail, and remove what he regards as mistakes in the conception of the good life in Plato.


English translations of Plato's Republic and Aristotle's Nicomachean Ethics are freely available in the Perseus Digital Library. These translations are older but more than good enough.

For newer translations, I recommend Plato. Republic (Translated from the New Standard Greek Text, with Introduction, by C. D. C. Reeve (Hackett Publishing, 2004)) and Aristotle. Nicomachean Ethics, 2nd edition (Translated, with Introduction, by Terence Irwin (Hackett Publishing, 2000)). These translations are relatively inexpensive, and you may find them more convenient to use than the digital translations in the Perseus Digital Library.

In addition to the links to the two texts, I provide a link to background notes on ancient Greek philosophy I use in my undergraduate history of ancient philosophy survey course.


The letter grade for the course is a function of the point grades on five writing assignments, six discussion posts, and a bibliography project. Each writing assignment is worth 10 points. Each discussion post is worth 5 points. The bibliography project is worth 20 points.

In a discussion post, you are to call attention to something in the reading you found interesting and you are to explain why you found it interesting. These posts must be thoughtful. Discussion posts written with little care and attention to detail will not receive full credit.

In the writing assignments, your answer should demonstrate that you understand the historical and philosophical issues related to the question. A good way to demonstrate your understanding is to provide answers understandable to someone who does not already know the answer.

The subjects of your discussion posts and writing assignments must be different.

In the bibliography project, you are to analyze five academic journal articles or book chapters from the scholarly literature on issues related to the Republic or Nicomachean Ethics.

The assignments (50 points), discussions (30 points), and bibliography project (20 points) total to 100 points. There is no extra credit, and late work is not accepted without good reason. The point total determines the letter grade: A+ (100-97), A (96-94), A- (93-90), B+ (89-87), B (86-84), B- (83-80), C+ (79-77), C (76-70), D (69-60), E (59-0). Incompletes are given only to accommodate serious illnesses and family emergencies, which must be adequately documented.


Plato, 427-347 BCE.
Aristotle, 384-322 BCE.

Πολιτείᾳ is the Greek title of the Republic.

"[I]t is possible for the citizens to have children, wives and possessions in common with each other, as in Plato's Republic (Πολιτείᾳ), in which Socrates says that there must be community of children, women and possessions" (Aristotle Politics II.1261a).)

The English title 'Republic' derives from the Latin res publica, which is the subject of Cicero's De re publica (or "About the res pubica").
We will read most of Plato's Republic and Aristotle's Nicomachean Ethics. Our interest is primarily historical. We want to know what Plato and Aristotle thought and why they thought it.

Plato and Aristotle write from their points of view in ancient Athens in the 5th to 4th century BCE. Our points of view are obviously different, and so it should not be surprising if some of their views about justice and the good life seem implausible to us. This, however, is not a cause for disappointment. It gives us the opportunity to think about the assumption or assumptions that set us apart and to think about the reasons for the truth of these assumptions.


Socrates, 470-399 BCE.
Plato was in the circle around Socrates. In 399 BCE, when Plato was in his late twenties, the city of Athens executed Socrates. Sometime after that, Plato began writing works in dialogue form. The Republic is traditionally thought to be one of the greatest of these dialogues.

Among Plato's dialogues, only the Laws is longer.

Socrates' interlocutors in the Republic are Cephalus, Polemarchus, Thrasymachus, and Plato's brothers (Gluacon and Adeimantus).

Socrates (Σωκράτης)
Cephalus (Κέφαλος)
Polemarchus (Πολέμαρχος), son of Cephalus
Thrasymachus (Θρασύμαχος)
Glaucon (Γλαύκων)
Adeimantus (Ἀδείμαντος)
The Republic consists in ten books.

It is not possible to read and think carefully about all of the Republic in the alloted time in this course, but the goal is to read large stretches of it and to think carefully about the parts of the conversation that make the most important contributions to the argument.


There are two main questions in Book I: what justice is and whether the just life is better than the unjust life. Look for those questions as you read. Think about what they are asking.

The "function" argument presupposes a certain way of thinking about the two main questions. To know whether the just life is better, we need to know what justice adds to a life. To know that, we need to know what justice is. In the "function" argument, justice is a property of the soul.

How Socrates (the character in the Republic) understands the soul is part of a long discussion, but initially we can think of the soul as a cognitive mechanism in terms of which a human being acts the way he does. So as a property of the soul, justice makes a human being live a certain life.

The question, then, is what this life is and whether it is better than the life in which the soul lacks justice.

The more common way of thinking about justice and whether it is better was the one Glaucon describes. In this description, justice is not a property of the soul. It is a kind of social agreement or convention among human beings that provides a certain amount of freedom for individuals to work out and live lives that they recognize as good.

Given what Glaucon says about human beings and justice, it can appear that the unjust life is better if the person living the unjust life can get away with his injustices. The reason is that the person appears freer to live as he wants.

The appearance that this unjust life is better presupposes a conception of human beings and the good life that Socrates rejects. So to show that the common way of thinking is wrong, Socrates sets out a theory of justice that has its basis in a different conception of human beings and the good life. This convinces Glaucon because he comes to see that the conception of human beings and the good life is correct.
In Book I, the "function" argument (Socrates presses against Thrasymachus) looks forward to the more detailed argument he sets out in the subsequent books of the Republic to show that the just life is better than the unjust life. Think about the conception of human beings that underlies the idea that they have souls, that the soul has a function, and that justice is its virtue.

In Book II, there are several important developments. The first is the challenge Glaucon puts to Socrates. He sets out a common way of thinking about justice and whether the just life is better, and he challenges Socrates to prove that this conception is mistaken. Think about the conception of human beings underlies the conception of justice that Glaucon sets out.

Post questions if you think or worry that you do not understand. Try to answer questions your classmates post. This will solidify your understanding of the issues. If you do not understand a response, follow up. It often takes some back and forth to move forward in philosophy.

The Text for Unit 1:

Republic I.327a-328c.   The opening scene.
Republic I.328c-331d.   Socrates talks with Cephalus.
Republic I.331d-336b.   Socrates talks with Polemarchus.
Republic I.336b-354b.   Socrates talks with Thrasymachus.
Republic I.354b-354c.   The conversation ends in perplexity.

Republic II.357a-358e.  Glaucon takes up the argument and challenges Socrates.

  "[W]e have not invoked the rewards and reputes of justice as you said Homer and Hesiod do, but we have proved that justice in itself is the best thing for the soul itself, and that the soul ought to do justice whether it possess the ring of Gyges or not, or the helmet of Hades to boot.
  Most true, Socrates" (Republic X.612b).

In Greek myth, the helmet of Hades (like the ring of Gyges) makes its wearer invisible.

Republic II.358e-362d.  Glaucon sets out the origin and nature of justice.
Republic II.362d-367e.  Adeimantus clarifies Glaucon's challenge.

Writing Assignment:
Assignment #1
You are free to discuss the assignment and to post questions about it.


In Book II, Socrates sets out a plan to determine what justice is. The plan is first to consider what justice is in a city and then to consider what justice is in an individual human being.

  "The origin of the city (πόλις),then, in my opinion, is to be found in the fact that we do not severally suffice for our own needs, but each of us lacks many things. Do you think a city is founded on any other principle?
  No other, Socrates.
  As a result of this, then, one man calling in another for one service and another for another, we, being in need of many things, gather many into one place of abode as associates and helpers, and to this dwelling together we give the name city. And between one man and another there is an interchange of giving, if it so happens, and taking, because each supposes this to be better for himself" (Republic II.369b).
To determine what justice is in a city, Socrates describes what he takes to be a rightly founded and thus completely good city. He then looks for what justice is in it. Think about what rightly founded is, whether a rightly founded city is good, and whether looking for justice in a rightly founded city is an appropriate strategy for coming to know what justice in a city is.

"The matter begins to be difficult when you ask whether we do all these things with the same thing or whether there are three things and we do one thing with one and one with another--learn with one part of ourselves, feel anger with another, and with yet a third desire the pleasures of nutrition and generation and their kind, or whether it is with the entire soul that we function in each case when we set out for something" (Republic IV.436a).

"Socrates, I think that from this point on our inquiry becomes an absurdity—if, while life is thought to be intolerable with a ruined constitution of body even if accompanied by all the food and drink and wealth and power in the world, yet we are to inquire whether life is going to be worth living when our soul, the very thing by which we live, is disordered and corrupted (ταραττομένης καὶ διαφθειρομένης), if one can do as he pleases, but cannot do that which will rid him of evil and injustice and make him possessed of justice and virtue" (Republic IV.444e).
Once Socrates thinks he knows what justice is in a city, he turns to the question of what justice is in an individual human being. To come to know the answer to this question, he argues for what historians call Plato's Tripartite Theory of the Soul. Think carefully about this argument. Identify its premises and conclusion. Think about the meaning of the terms in the premises and the conclusion. Think about the evidence for the truth of the premises.

Given the tripartite conception of the human soul, Socrates identifies what justice is in an individual human being. Think about what he says this justice is. Given this conception of justice in a human being, think about the life that characterizes a just human being.

Glaucon, at this point, given the conception of justice in an individual, tells Socrates that it has become ridiculous to think that unjust life is better. Socrates replies that nonetheless it is important to give the proof. He moves in this direction with a discussion of the forms of vice.

The Text for Unit 2:

Republic II.368c-369b.      The plan is to search for justice in a city and in a human being.
Republic II.369b-372e.      The reason human beings organize themselves into a city.
Republic II.372e-374d.      The birth of a luxurious city.
Republic II.374d-III.412c. The education of the guardians.
Republic III.412c-414b.     The rulers are the best of the guardians.
Republic III.414b-417b.     The second-best among the guardians are auxiliaries.
Republic IV.419a-427d.     The aim is not to make one class outstandingly happy.
Republic IV.427d-434d.     What justice is in the city.
Republic IV.434d-435c.     What justice is in the individual human being.
Republic IV.435c-444e.      The Tripartite Theory of the Soul.
Republic IV.444e-445c.       Now it seems obvious that the just life is better.
Republic IV.445c-V.449b.  The forms of vice.

Writing Assignment:
Assignment #2
You are free to discuss the assignment and to post questions about it.


In Book IV, given the conception of what justice is in a individual human being in terms of the parts of the soul, Glaucon thinks that it has become absurd to inquiry further into whether the just life is better than the unjust life. He thinks it obvious that the just life is better.

Socrates agrees it is absurd, but to make the truth about the just life as plain as possible, he urges that they should continue their inquiry into the just life and the unjust life.

He has described justice in the city and in the individual, so Socrates turns to the four kinds of the unjust cities and unjust individuals. Polemarchus and Adeimantus, however, intervene to ask for a more complete explanation of marriage and family life in a just city.

"Unless either philosophers [or: lovers of wisdom (φιλόσοφοι)] become kings in our states or those whom we now call our kings and rulers take to the pursuit of philosophy seriously and adequately, and there is a conjunction of these two things, political power and philosophy, while the motley horde of the natures who at present pursue either apart from the other are compulsorily excluded, there can be no cessation of troubles, dear Glaucon, for our states, nor, I fancy, for the human race either" (Republic V.473c).

"[T]hose [selected to be guardians] who have survived the tests and approved themselves altogether the best in every task and form of knowledge must be brought at last to the goal. We shall require them turn upwards the vision of their souls and fix their gaze on that which sheds light on all, and when they have thus beheld the good itself (τὸ ἀγαθὸν αὐτό) they shall use it as a pattern for the right ordering of the state and the citizens and themselves throughout the remainder of their lives, each in his turn, devoting the greater part of their time in the love of wisdom (φιλοσοφίᾳ), but when the turn comes for each, toiling in the service of the state and holding office for the city's sake, regarding the task not as a fine thing but a necessity; and so, when each generation has educated others like themselves to take their place as guardians of the state, they shall depart to the Islands of the Blest and there dwell. And the state shall establish public memorials and sacrifices for them as to divinities if the Pythian oracle approves or, if not, as to happy and godlike men (εὐδαίμοσί τε καὶ θείοις)" (Republic VII.540a).

Translators often render the noun φιλοσοφία and adjective φιλόσοφος into English as "philosophy" and "philosopher." These words transliterate as philosophia and philosophos.
Once Socrates has given a more complete explanation, explained that justice requires the rulers to be lovers of wisdom, and explained the education to produce them, he returns to the unjust cites and individuals. He notes that they "have already described the man corresponding to aristocracy or the government of the best, whom we rightly say to be good and just" (Republic VIII.544e) and goes on to complete his description of the unjust cities and individuals. When he does, he asks Glaucon whether he can proclaim on his behalf that "the best man and the most just to be the happiest (εὐδαιμονέστατον), and that he is the most kingly, the one who most rules like a king over himself" and "that the worst and most unjust is the most unhappy, and that he is the most tyrannical, the one who is most a tyrant over himself" (Republic IX.580b). Once Glaucon agrees, Socrates concludes that "this, then, would be one of our proofs...."

A life in "philosophy" (φιλοσοφία) is an unusual life. To begin to see this, think about how Socrates understands reason, how he understands reason in a life in the love of wisdom. and why he thinks this life is so much better than a life in which reason is not in control.

The Text for Unit 3:

Republic V.449b-472a.          Women and children and related matters.
Republic V.472a-VI.502d.     The rulers in a just city must be lovers of wisdom.
Republic VI.502d-VII.541b.  The training necessary to become a lover of wisdom.
Republic VIII.543a-IX.580a. The kinds of corrupted cities and characters.
Republic IX.580b-580d.          First in happiness.
Republic IX.580d-592b.          First in pleasure.
Republic X.595a-608d.            Imitation.
Republic X.608d-612b.           The immortality of the soul
Republic X.612b-621d.           The myth of Er.

Writing Assignment:
Assignment #3
You are free to discuss the assignment and to post questions about it.

THE NICOMACHEAN ETHICS The title seems to refer to Aristotle's son, Nicomachus, who may have edited the Nicomachean Ethics.

Aristotle was a member of Plato's Academy for twenty years. He entered in 367 BCE when he was seventeen and remained until 347 BCE, the year of Plato's death.

"Aristotle, son of Nicomachus and Phaestis, was a native of Stagira. His father, Nicomachus, as Hermippus relates in his book On Aristotle, traced his descent from Nicomachus who was the son of Machaon and grandson of Asclepius; and he resided with Amyntas, the king of Macedon, in the capacity of physician and friend. Aristotle was Plato's most genuine disciple; he spoke with a lisp, as we learn from Timotheus the Athenian in his book On Lives; further, his calves were slender (so they say), his eyes small, and he was conspicuous by his attire, his rings, and the cut of his hair. According to Timaeus, he had a son by Herpyllis, his concubine, who was also called Nicomachus" (Digoenes Laertius, Lives of the Philosophers 5.1).

"To say that the best good is happiness will probably appear a truism; we still require a more explicit account of what this good is and thus what constitutes happiness. Perhaps we may arrive at this account by ascertaining the function (ἔργον) of man" (Nicomachean Ethics I.6.1097b).

"Life seems common even to plants, but we are seeking what is peculiar to man. So let us exclude the life of nutrition and growth. Next there would be a life of perception, but this also seems common to the horse, the ox, and every animal. The remaining possibility is a life of action of [the part of the soul] having reason (πρακτική τις τοῦ λόγον ἔχοντος)" (Nicomachean Ethics I.6.1097b).

"If we declare that the function (ἔργον) of man is a certain life, and that this is an activity and action of the soul with reason (ψυχῆς ἐνέργειαν καὶ πράξεις μετὰ λόγου), and that the good of man is to do this well and beautifully, and that if a function is completed well when it is completed in accordance with its proper virtue (οἰκείαν ἀρετὴν), then it follows that the good of man is the activity of his soul in conformity with virtue, or if there are several virtues, then in conformity with the best and most the end (τὸ ἀνθρώπινον ἀγαθὸν ψυχῆς ἐνέργεια γίνεται κατ᾽ ἀρετήν, εἰ δὲ πλείους αἱ ἀρεταί, κατὰ τὴν ἀρίστην καὶ τελειοτάτην). Moreover, to be happy takes a complete lifetime; for one swallow does not make spring, nor does one fine day; and similarly one day or a brief period does not make a man blessed and happy" (Nicomachean Ethics I.6.1098a).
Aristotle is the first great Platonist and Plato's first great critic. Aristotle accepts the broad outline of the Platonic framework, but he also corrects what he regards as its mistakes.

The Nicomachean Ethics consists in ten books.

In the Nicomachean Ethics, Aristotle does not set out his argument in dialogue form as Plato does in the Republic. Further, Aristotle's writing in the Nicomachean Ethics reads more like a series of notes than a finished work. This makes the argument initially difficult to see.

As with the Republic, it is not possible to read and think carefully about all of the Nicomachaean Ethics in the alloted time in this course. The goal is to read large stretches of it and to think carefully about the parts that make the most important contributions to the argument.


The subject of Aristotle's Nicomachean Ethics is the "end of the things we pursue in our actions," what he calls the "best good" for a human being (Nicomachean Ethics I.2.1094a).

Knowledge of this "best good," Aristotle says, "is of great importance for the conduct of our lives." If we have it, and so know what the good in a human life is, then, "like archers who have a target, we are more likely to do what is needed" (Nicomachean Ethics I.2.1094a).

Aristotle notes that it is generally agreed that the "best good" is "happiness" (εὐδαιμονία).

This agreement, however, as he also notes, is not very helpful because there is no agreement about what happiness is. So, to reach an understanding what happiness is, Aristotle considers what he calls the "function" (ἔργον) of a human being. He argues that this function is "action of [the part of the soul] having reason (πρακτική τις τοῦ λόγον ἔχοντος)."

Think about Aristotle's approach to the function of the soul and the one Socrates takes in Book I of the Republic. The functions they identify are different. Think about why.

Given that happiness for a human being consists in executing the human function well and that things perform their function well only if they have their proper virtue or virtues, Aristotle concludes that "happiness" and "the good of man" is

• "the activity of the soul in conformity with virtue, or if there are several
virtues, in conformity with the best and most the end among them."

It remains, then, to understand the part of the soul having reason, to identify its virtue or virtues, and to understand the life in which this part of the soul has these virtues.

Aristotle thinks that the part of the human soul having reason has two parts: a part with reason and a part with reason as its controller. Further, he divides the part with reason into a part that reasons about theoretical matters and a part that reasons about practical matters.

Aristotle thinks that the virtues proper to these first two parts of the soul (the part with reason and part with reason as its controller) are the virtues of "thought" and virtues of "character."

The Text for Unit 4:

Nicomachean Ethics I.1094a-I.1096a.        The good that is the aim of politics.
Nicomachean Ethics I.1097b-I.1098a.        The argument from function.
Nicomachean Ethics I.1102a-II.1109b.       Virtue and the soul.
Nicomachean Ethics III.1109b-1115a.        Necessary conditions for virtue.
Nicomachean Ethics III.1115a-IV.1128b.  Virtues of character.
Nicomachean Ethics V.1129a-1138b.          Justice.

Writing Assignment:
Assignment #4
You are free to discuss the assignment and to post questions about it.


For Aristotle, although the text contains no very clear statement of the position, it seems that the virtues of thought in the good life for a human being are "wisdom" (σοφία) and "practical wisdom" (φρόνησις). Wisdom is the virtue proper to the first part of the part of the soul having reason. This is the part suited to "knowledge," the part Aristotle calls the ἐπιστημονικὸν, epistēmonikon, adjective

λογιστικόν, logistikon, adjective
ἐπιστημονικὸν. Practical wisdom is the virtue proper to the second part of the part of the soul having reason. This is the part suited to "calculating," the part Aristotle calls the λογιστικόν.

Aristotle, it seems, thinks that the virtues of character ("courage" (ἀνδρεία), "temperance" (σωφροσύνη), and so on) are necessary for practical wisdom and further, although this is less clear, that practical wisdom is necessary in human beings for the acquisition of wisdom.

Further, although again the text is not very clear, Aristotle seems to think the good life for a human being takes two forms: (i) a life with both practical wisdom and wisdom and (ii) a life with practical wisdom but without wisdom. The first is the best life for a human being.

If this interpretation is correct, then contrary to the Platonic conception of the good life as a life of contemplation, wisdom is not a necessary condition for "happiness" (εὐδαιμονία).

Aristotle does not explain this opposition to the Platonic conception, but he may have Socrates in mind. Plato, in thinking about Socrates, understands the good life in a way that excludes the life Socrates lived (a life, in Aristotle's terms, of practical wisdom but without wisdom). It is possible that Aristotle thinks that this is a mistake and that although Socrates did not achieve the best form of the good life, his life is an example of the second form of the good life.

The Text for Unit 5:

Nicomachean Ethics VI.1138b-1145a.          Virtues of thought.
Nicomachean Ethics VII.1145a-1154b.         Continence, incontinence, pleasure.
Nicomachean Ethics VIII.1155a-IX.1172a.   Friendship.
Nicomachean Ethics X.1172a-1181b.             Pleasure, happiness, legislation.

Writing Assignment:
Assignment #5
You are free to discuss the assignment and to post questions about it.


Writing Assignment:
Bibliography Project
You are free to discuss the assignment and to post questions about it.

Contact Information

Thomas A. Blackson
Philosophy Faculty
School of Historical, Philosophical, and Religious Studies
Lattie F. Coor Hall, room 3356
PO Box 874302
Arizona State University
Tempe, AZ. 85287-4302,, www.public.asu/~blackson