Wisdom from the Early Stoics, Zeno of Citium 20

Diogenes of Ptolemas, it is true, begins with Ethics; but Apollodorus puts Ethics second, while Panaetius and Posidonius begin with Physics, as stated by Phanias, the pupil of Posidonius, in the first book of his Lectures of Posidonius. 

Cleanthes makes not three, but six parts, Dialectic, Rhetoric, Ethics, Politics, Physics, Theology. But others say that these are divisions not of philosophic exposition, but of philosophy itself: so, for instance, Zeno of Tarsus. 

Some divide the logical part of the system into the two sciences of rhetoric and dialectic; while some would add that which deals with definitions and another part concerning canons or criteria: some, however, dispense with the part about definitions.

Now the part which deals with canons or criteria they admit as a means for the discovery of truth, since in the course of it they explain the different kinds of perceptions that we have. And similarly the part about definitions is accepted as a means of recognizing truth, inasmuch as things are apprehended by means of general notions. 

Further, by rhetoric they understand the science of speaking well on matters set forth by plain narrative, and by dialectic that of correctly discussing subjects by question and answer; hence their alternative definition of it as the science of statements true, false, and neither true nor false.

Rhetoric itself, they say, has three divisions: deliberative, forensic, and panegyric.

Rhetoric according to them may be divided into invention of arguments, their expression in words, their arrangement, and delivery; and a rhetorical speech into introduction, narrative, replies to opponents, and peroration.

Dialectic, they hold, falls under two heads: subjects of discourse and language. 

And the subjects fall under the following headings: presentations and the various products to which they give rise, propositions enunciated and their constituent subjects and predicates, and similar terms whether direct or reversed, genera and species, arguments too, moods, syllogisms and fallacies whether due to the subject matter or to the language; these including both false and true and negative arguments, sorites and the like, whether defective, insoluble, or conclusive, and the fallacies known as the Veiled, or Horned, No man, and The Mowers.

The second main head mentioned above as belonging to Dialectic is that of language, wherein are included written language and the parts of speech, with a discussion of errors in syntax and in single words, poetical diction, verbal ambiguities, euphony and music, and according to some writers chapters on terms, divisions, and style.  

—Diogenes Laërtius, 7.41-44

IMAGE: Antonio Zucchi, A Greek Philosopher and His Disciples (1767)