Hellenistic Epistemology

Syllabus. PHI 420: Topics in Philosophy. The Stoics and the Academics

Instructor: Thomas A. Blackson

PHI 328 (History of Ancient Philosophy) or its equivalent is helpful but not necessary for this course.

This course is conducted through the Learning Management System that ASU uses for its online programs.

The Stoics and Academics are "Hellenistic" philosophers. They lived in the Hellenistic Age (the period from the death of Alexander the Great in 323 BCE to the end of the Roman Republic in 31 BCE). This is not a period in the history of philosophy, but together with the Epicureans these philosophers form a group because they are united in their opposition to what they thought were the excesses of the prior classical tradition, the tradition of Plato and Aristotle. In about 100 BCE, this opposition to the classical tradition disintegrated as non-skeptical forms of Platonism underwent a resurgence and eventually gave rise to early forms of Christianity. This resurgence traditionally marks the end of the Period of Schools, the second of the three periods in which historians divide ancient philosophy.

Cicero, 106 - 43 BCE. He writes in the generation after the collapse of the New Academy.

Cicero refers to his "Academics" (or: "[views] of or pertaining to the Academy") (On Duties 2.8).

The Latin adjective academicus (a transliteration of the corresponding Greek adjective ἀκαδημικός) means "relating to the Academy, Academic." When the adjective is used substantively (without a noun), it means "an Academic philosopher" (a philosopher who adheres to the position of the Academy, typically the position of the "New" Academy, the Academy in the time of Arcesilaus to Philo).

Cicero heard Philo's lectures in Rome in 88-87 BCE (Brutus 306) and Antiochus' lectures in Athens in 79-77 BCE (Acaemica 1.14). Antiochus became a member of the Academy at about the time Philo became head, was initially a follower of Philo, but later broke with him (Academica II.69).

Cicero thinks of himself as an adherent of the philosophy of the New Academy (On Duties 2.7-8; cf. 3.20).

The New Academy:

Arcesilaus, 4th to middle 3rd century BCE. He succeeded Crates (the fifth head of the Academy) and changed the focus of the Academy from theory to questioning. His headship marks the beginning of the "New" Academy.

Carneades, late 3rd to late 2nd century BCE. He is Arcesilaus' most distinguished successor. He took important steps to clarify the Academic position against the Stoics.

Clitomachus, early 2nd to late 2nd century BCE. He succeeded Carneades. Carneades introduced the "persuasive" impression. Clitomachus worked out an interpretation of what Carneades had in mind.

Philo of Larisa, middle 2nd to early 1st century BCE. He proposed an alternative interpretation of Carneades and the "persuasive" impression. Philo also rejected the Stoic conception of knowledge and proposed an alternative.

Philo was the last head of the New Academy. In 88 BCE, during the Mithridatic War, Philo fled Athens and took refuge in Rome. In 86 BCE, Sulla destroyed the grounds of the Academy in his siege of Athens. Philo died a few years later. After his death, the Academy (whose grounds had already been destroyed) disappeared into two rival factions.

Antiochus, late 2nd to middle 1st century BCE. He broke from Philo and tried to reestablish the "Old" Academy. This contributed to the renewed interest in non-skeptical forms of Platonism that marks the end of the Period of Schools.

Aenesidemus, late 2nd to middle 1st century BCE. He broke from Philo to found a new skeptical school under the name of Pyrrho (middle 4th to early 3rd century BCE). This new school continued into about the 3rd century CE.
The debate on the nature and possibility of knowledge between the Stoics and the Academics is one of the most famous debates in the history of philosophy. In this course, we consider the reasons the Stoics and the Academics had for their positions. Our interest in these positions is primarily historical. We want to know what the Stoics and Academics thought, but we also consider some of the philosophical issues that motivated their positions.


The Stoics take their name from their initial meeting place in the Ποικίλη Στοά ("Painted Stoa").

A στοά is a roofed colonnade. The adjective ποικῐ́λη means "many-colored." The Ποικίλη Στοά derived its name from the paintings that decorated its walls.

Steps of the Poikile Stoa
The west end steps of the Ποικίλη Στοὰ. In the foreground is part of the foundation for the Hellenistic Gate, which allowed access to the Agora from the north.

Early Stoicism:

Zeno of Citium, late 4th to middle 3rd century BCE. He founded the Stoic school in about 300 BCE.

Cleanthes, late 4th to late 3rd century BCE. He succeeded Zeno as head of the school.

Chrysippus, early 3rd to late 3rd century BCE. He was the third and most influential head of the Stoic school.

Middle Stoicism:

Panaetius of Rhodes, late 2nd to early 2nd century BCE. He succeeded Antipater of Tarsus in about 129 BCE to become the seventh head of the Stoic school in Athens.

Posidonius of Apameia, early 2nd to middle 1st century BCE. He was polymath whose writings have survived only in fragments.

Late Stoicism:

Seneca, late 1st century BCE to middle 1st century CE.

Epictetus, middle 1st to late 2nd century CE.

Marcus Aurelius, 121-180 CE. He was Roman Emperor from 161-180 CE.


The reading for the course is from the ancients and from the secondary literature.

From the ancients, the Academica is the primary text. Our knowledge of what the Stoics and the Academics thought depends heavily on the speeches in this work. Cicero, in 46-44 BCE, toward the end of his life, wrote a series of works to present the philosophy of the schools (which had been written in Greek) in his native Latin. (He describes his intention in On Ends I.1-4.) The Academica is reconstructed from two works Cicero wrote in this period.

The contemporary literature on the Stoics and Academics is voluminous. The focus in this course is on some of the work that sets out a now standard interpretation of the debate.

All the readings for this course are linked through this syllabus. Most are available to anyone on the internet. The others are available through the ASU library with an ASURITE ID.


The letter grade for the course is a function of the point grades on four writing assignments, five discussion posts, and a bibliography project. Each writing assignment is worth 10 points. Each discussion post is worth 8 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. The best way to demonstrate your understanding is to provide answers helpful to someone who does not already know the answer.

In the bibliography project, you are to analyze five academic journal articles or book chapters from the scholarly literature on issues related to the debate between the Stoics and the Academics. At most two of the articles or book chapters can be from the syllabus. The bibliography project consists in the notes you take in the research your conduct prior to writing a paper.

The assignments (40 points), discussions (40 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.


The goal is to understand the debate between the Stoics and the Academics on the nature and possibility of knowledge. The Academica is the primary evidence for the debate.

The Academica is reconstructed from fragments of two of Cicero's works. The first (the Academica Priora) consisted in the now lost Catulus and in the Lucullus. The second (the Academica Posteriora), which was Cicero's revised edition of the first, consisted in four books and was entitled the Academic Books. Only part of the first of the Academic Books has survived.

Academica I is the surviving part of book I of the Academic Books. Academica II is the Lucullus.

Academica I is Varro's speech on the history of philosophy according to Antiochus (Academica I.15–42) and Cicero's alternative from an Academic point of view (Academica I.43-46).

Academica II is Lucullus' speech on Stoic epistemology (Academica II.10–62) and Cicero's speech in reply from an Academic point of view (Academica II.64–147).

In each unit but the last, we read excerpts from the Academica on the debate between the Stoics and the Academics. To help make the debate understandable, I supply an explanation of the main points for each unit. We also read some of the contemporary historical analysis of the debate. This analysis is restricted primarily to the work of Michael Frede, whose work on the Stoics, the Academics, and their debate have become classics in the history of philosophy.


The Stoics have a theory about the nature and possibility of knowledge.

They thought that knowledge is possible because there are "cognitive impressions." Impressions are representations. In adults, the contents of impressions are propositions. So, for example, when someone says "I have the impression that this rose is dark red," he has an impression whose content is the proposition "that this rose is dark red." Unlike impressions generally, cognitive impressions only have true propositions as their contents. Nature in its providence constructs human beings with the ability to "assent" to these impressions and thus makes it possible for them to have the knowledge necessary to live good lives. Assent issues in the attitude of belief toward the propositional content of the impression, and assent to a cognitive impression issues in the belief they call "cognition." All cognitions are true, but not all cognitions are "knowledge." Knowledge, according to the Stoics, is an attitude formed in an assent that no rational means can force one to withdraw. They thought that this was the lesson of Socrates. As they understood him, although he thought knowledge was possible, he thought that no one has knowledge because no one can see his way through his questioning. He always forces his interlocutors to withdraw their assent. The Stoics thought that in this way he shows that his interlocutors have "opinions."


A good way to approach these readings is with questions in mind. Look for answers to

What is an impression?
What is assent?
What is a cognitive impression?
What is cognition?
What is knowledge and how does it involve cognition?

In addition, think about the philosophical question of whether the Stoic epistemology is plausible. In particular, think about whether they are right about what knowledge is.

• Selected passages from Cicero (and Sextus Empiricus and others) about the Stoics.

Sextus Empiricus (2nd or 3rd century CE) was a physician (in the empirical tradition) and philosopher (in the Pyrrhonian tradition).

In a list of Empiricist physicians, Diogenes Laertius mentions "Sextus the Empiricist" (Σέξτος ὁ ἐμπειρικός) (Lives of the Philosophers IX.116). In Against the Grammarians, Sextus Empiricus says that he himself wrote a (now lost) set of discourses on Empiricism (Against the Grammarians, 61).

Sextus Empiricus' surviving works include the Outlines of Pyrrhonism and the works preserved under the title Against the Mathematicians (Adversus Mathematicos).

Against the Mathematicians (referred to by the abbreviation M) is in eleven books that have separate titles:

Against the Grammarians is M I
Against the Rhetoricians is M II
Against the Geometers is M III
Against the Arithmeticians is M IV
Against the Astrologers is M V
Against the Musicians is M VI
Against the Logicians I and II is M VII and M VIII.
Against the Physicists I and II is M IX and M X
Against the Ethicists is M XI.

• "Stoic epistemology," Michael Frede.
• "Stoics and Skeptics on Clear and Distinct Impressions," Michael Frede, 151-163, 166-170.

Writing Assignment:

You are free to discuss the assignment and to post questions about it.

Assignment #1


A new outlook entered the Academy in 265 BCE with Arcesilaus, who succeeded Crates as the sixth head of the school Plato founded almost a hundred years previously in 387 BCE. Arcesilaus refocused the Academy by interpreting Plato's dialogues in terms of the Socratic practice of questioning to expose the pretense to wisdom. The Academics took the Stoics and their pronouncements in epistemology as their primary targets in this questioning.

Against the Stoics, in the manner of Socrates, the Academics argue that no impression is cognitive because for every true impression there is a false impression indistinguishable from it. On the basis of this premise, the Academics invite the Stoics to admit that it is necessary to withhold assent.

  1. For every true impression, there is a false impression indistinguishable from it.
  2. If (1) is true, then no impression is cognitive.
  3. If no impression is cognitive, then it is necessary to withhold assent.
  4. It is necessary to withhold assent.

The Stoics accept premises (2) and (3). The Academics argue for premise (1) on the basis of the impressions of apparently indistinguishable objects (such as identical twins) and on the basis of states of mind such as dreaming or madness in which false impressions are indistinguishable from the true impressions one has when one is not dreaming or not suffering a fit of madness.

Some Online Resources:

ASU Research Databases: Philosophy
ASU Research Databases: Classics

Perseus Collection. Greek and Roman Materials

Stanford Encyclopedia of Philosophy:
Ancient Skepticism
Antiochus of Ascalon
Philo of Larissa

Essays in Ancient Philosophy, Michael Frede

Loeb Classical Library:
Academica, Cicero
Against the Logicians, Sextus Empiricus

On Academic Scepticism, Charles Brittain

History of Philosophy without any gaps: The New Academy


• Selected passages from Cicero (and Sextus Empiricus and Diogenes Laertius).
• "The sceptics," Michael Frede, 262-280.
• "Introduction," On Academic Scepticism, Charles Brittain, xix-xxiii.

Writing Assignment:

You are free to discuss the assignment and to post questions about it.

Assignment #2


In the Academy, there was a problem about how to understand their relation to the argument they pressed against the Stoics. This problem started with Arcesilaus.

In opposition to the Stoic view about the possibility of knowledge, Arcesilaus seems to have said that "there is nothing that can be known" and that therefore "no one must make any positive statement or affirmation or give the approval of his assent to any proposition" (Academica I.45). Given that he did say this and that in saying this he did not straightforwardly contradict himself, he cannot be understood to have assented to the view that no one should assent to any view. Still, because it remained unclear exactly how he should be understood, it became a problem within the Academy to understand his opposition to the Stoic pronouncements in epistemology. This opposition had become a defining feature of the Academy, and there was a worry that the integrity of the school would be undermined if the problem went unsolved.

Carneades (who became head of the Academy sometime before he was part of the Athenian embassy to Rome in 155 BCE) seems to have taken the first important step in explaining how the Academics can argue against the Stoics without assenting to the view that no one should assent to any view. He seems to have thought that assent is permitted to "persuasive impressions."

The Academics offer the Stoics an argument that would expose their pretense to wisdom if they were to accept it. In doing this, the Academics need not assent to any of the premises of the argument. At the same time, given that they can assent to "persuasive impressions," nothing prevents them from assenting to the impression that no impression is cognitive and that the Stoics should accept the argument. They can think that although the Stoics should withhold assent, they are free to assent both in respect to the argument and in their lives more generally.


In these readings, look for answers to these questions

What is a persuasive impression?
How is a persuasive impression different from a cognitive impression?
What kind of assent is permissible for the Academic?
What kind of assent is forbidden for the Academic?

• Selected passages from Cicero and Sextus Empiricus.
• "The Skeptic's Two Kinds of Assent," Michael Frede.
• "Introduction," On Academic Scepticism, Charles Brittain, xxiii-xxxi.

Writing Assignment:

You are free to discuss the assignment and to post questions about it.

Assignment #3


A dispute developed within the Academy between successors to Carneades. Clitomachus (who became head of the Academy after Carneades) and the Clitomachians were on one side of this dispute. Philo (who became head of the Academy after Clitomachus) and the Philonian/Metrodorians were on the other side. Metrodorus was a follower of Carneades. Cicero refers to Philo and Metrodorus together in opposition to the interpretation of Carneades that Clitomachus and the Clitomachians championed (Academica II.78). The evidence is extremely limited, but the dispute seems to have been over the justification of assent to persuasive impressions. Clitomachus and Philo followed Carneades in thinking that it is rational to assent to these impressions, but they offered different explanations of the justifications of this assent.


In these readings, look for answers to these questions

What is the Stoic justification for assenting to cognitive impressions?
Why is the Academic justification for assenting to persuasive impressions?

• Selected passages from Cicero and Sextus Empiricus.
• "Epistemology from an Evaluativist Perspective," Hartry Field.
• "Academic Justifications of Assent," Tom Blackson.

Writing Assignment:

You are free to discuss the assignment and to post questions about it.

Assignment #4


After Philo died in 84 or 83 BCE, the Academy disintegrated into rival factions.

Photius reports that Aenesidemus (in a now lost work) says that "the Academics, especially the ones now, ... appear to be Stoics fighting with Stoics" (Bibliotheca 212.170a)

"[This school of thought is called] 'Pyrrhonean (Πυρρώνειος)' from the fact that Pyrrho appears to us to have applied himself to Scepticism more thoroughly and more conspicuously than his predecessors" (Sextus Empiricus, Outlines of Pyrrhonism I.1.7).

Photius (9th century CE) was Ecumenical Patriarch of Constantinople. His Bibliotheca consists in notices of works in his library, almost half of which are now lost.

Notice 212 is a short notice of "the eight books of Pyrrhonian Writings (Πυῤῥωνίων λόγοι) by Aenesidemus" (Bibliotheca 212.169b). Photius states the purpose of the work and describes the contents of each book. He includes some extracts in these descriptions.

Βιβλιοθήκη means "library, collection of books."
Aenesidemus (1st century BCE) headed one of these factions. He broke from Philo to found a new skeptical movement named after Pyrrho (middle 4th to early 3rd century BCE), who seems to have pursued a skeptical way of life but wrote nothing and established no school.

Most of what is known about the Pyrrhonians depends on Sextus Empiricus (2nd or 3rd century CE). His Outlines of Pyrrhonism sets outs what the Pyrrhonians thought.


In these readings, look for answers to this question

How do the Pyrrhonians distinguish themselves from the Academics?

• Selected passages from Sextus Empiricus.
• "The sceptics," Michael Frede, 280-284.
• "An empiricist view of knowledge: memorism," Michael Frede.

Writing Assignment:

You are free to discuss the assignment and to post questions about it.

Bibliography Project

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
blackson@asu.edu, tomblackson.com, www.public.asu/~blackson