Vitae philosophorum

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[*](The word φαντασία (= appearance or appearing) is a technical term in Stoic logic for which no one English equivalent is as yet unanimously adopted. It denotes the immediate datum of consciousness or experience, whether presented to sense or in certain cases to the mind. Hence presentation is nearer than perception or impression. It might be thought to correspond to Locke’s simple ideas, for which Hume substituted impressions and ideas; but this is hardly so; for φαντασίαι are given as it were from without, and then with them as materials the mind itself constructs general notions and concepts.) 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

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.

The study of syllogisms they declare to be of the greatest service, as showing us what is capable of yielding demonstration; and this contributes much to the formation of correct judgements, and their arrangement and retention in memory give a scientific character to our conception of things.

An argument is in itself a whole containing premisses and conclusion, and an inference (or syllogism) is an inferential argument composed of these. Demonstration is an argument inferring by means of what is better apprehended something less clearly apprehended.

A presentation (or mental impression) is an imprint on the soul: the name having been appropriately borrowed from the imprint made by the seal upon the wax.

There are two species of presentation, the one apprehending a real object, the other not. The former, which they take to be the test of reality, is defined as that which proceeds from a real object, agrees with that object itself, and has been imprinted seal-fashion and stamped upon the mind:

Dialectic, they said, is indispensable and is itself a virtue, embracing other particular virtues under it.[*](Cf.Plut.Mor.874 e, and inf. §§ 62, 83.) Freedom from precipitancy is a knowledge when to give or withhold the mind’s assent to impressions. By wariness they mean a strong presumption against what at the moment seems probable, so as not to be taken in by it.