Some again say that the logical division is properly subdivided into two sciences, namely, rhetoric and dialectics; and some divide it also into definitive species, which is conversant with rules and tests; while others deny the propriety of this last division altogether, and argue that the object of rules and tests is the discovery of the truth; for it is in this division that they explain the differences of representations. They also argue that, on the other side, the science of definitions has equally for its object the discovery of truth, since we only know things by the intervention of ideas. They also call rhetoric a science conversant about speaking well concerning matters which admit of a detailed narrative; and dialectics they call the science of arguing correctly in discussions which can be carried on by question and answer; on which account they define it thus: a knowledge of what is true, and false, and neither one thing nor the other.
Again, rhetoric itself they divide into three kinds: for one description they say is concerning about giving advice, another is forensic, and the third encomiastic; and it is also divided into several parts: one relating to the discovery of arguments, one to style, one to the arrangement of arguments, and the other to the delivery of the speech. And a rhetorical oration they divide into the exordium, the narration, the reply to the statements of the adverse party, and the peroration.
Dialectics, they say, is divided into two parts: one of which has reference to the things signified, the other to the expression. That which has reference to the things signified or spoken of, they divide again into the topic of things conceived in the fancy, and into those of axioms, of perfect determinations, of predicaments, of things alike, whether upright or prostrate, of tropes, of syllogisms, and of sophisms, which are derived either from the voice or from the things. And these sophisms are of various kinds: there is the false one, the one which states facts, the negative, the sorites, and others like these; the imperfect one, the inexplicable one, the conclusive one, the veiled one, the horned one, the nobody, and the mower.
In the second part of dialectics, that which has for its object the expression, they treat of written language, of the different parts of a discourse, of solecism and barbarism, of poetical forms of expression, of ambiguity, of a melodious voice, of music; and some even add definitions, divisions, and diction.
They say that the most useful of these parts is the consideration of syllogisms; for that they show us what are the things which are capable of demonstration, and that contributes much to the formation of our judgment, and their arrangement and memory give a scientific character to our knowledge. They define reasoning to be a system composed of assumptions and conclusions; and syllogism is a syllogistic argument proceeding on them. Demonstration they define to be a method by which one proceeds from that which is more known to that which is less. Perception, again, is an impression produced on the mind, its name being appropriately borrowed from impressions on wax made by a seal; and perception they divide into comprehensible and incomprehensible: Comprehensible, which they call the criterion of facts, and which is produced by a real object, and is therefore at the same time conformable to that object; Incomprehensible, which has no relation to any real object, or else, if it has any such relation, does not correspond to it, being but a vague and indistinct representation.
Dialectics itself they pronounce to be a necessary science, and a virtue which comprehends several other virtues under its species. And the disposition not to take up one side of an argument hastily, they defined to be a knowledge by which we are taught when we ought to agree to a statement, and when we ought to withhold our agreement. Discretion they consider to be a powerful reason, having reference to what is becoming, so as to prevent our yielding to an irrelevant argument. Irrefutability they define to be a power in an argument, which prevents one from being drawn from it to its opposite. Freedom from vanity, according to them, is a habit which refers the perceptions back to right reason.
Again, they define knowledge itself as an assertion or safe comprehension, or habit, which, in the perception of what is seen, never deviates from the truth. And they say further that without dialectic speculation, the wise man cannot be free from all error in his reasoning. For that that is what distinguishes what is true from what is false, and which easily detects those arguments which are only plausible, and those which depend upon an ambiguity of language. And without dialectics they say it is not possible to ask or answer questions correctly. They also add that precipitation in denials extends to those things which are done, so that those who have not properly exercised their perceptions fall into irregularity and thoughtlessness. Again, without dialectics, the wise man cannot be acute, and ingenious, and wary, and altogether dangerous as an arguer. For that it belongs to the same man to speak correctly and to reason correctly, and to discuss properly those subjects which are proposed to him, and to answer readily whatever questions are put to him, all which qualities belong to a man who is skillful in dialectics. This then is a brief summary of their opinions on logic.
And that we may also enter into some more minute details respecting them, we will subjoin what refers to what they call their introductory science, as it is stated by Diocles of Magnesia, in his Excursion of Philosophers, where he speaks as follows, and we will give his account word for word.
The Stoics have chosen to treat, in the first place, of perception and sensation, because the criterion by which the truth of facts is ascertained is a kind of perception, and because the judgment which expresses the belief, and the comprehension, and the understanding of a thing, a judgment which precedes all others, cannot exist without perception. For perception leads the way; and then thought, finding vent in expressions, explains in words the feelings which it derives from perception. But there is a difference between φαντασία and φάντασμα. For φάντασμα is a conception of the intellect, such as takes place in sleep; but φαντασία is an impression, τύπωσις, produced on the mind, that is to say, an alteration, ἀλλοίωσις, as Chrysippus states in the twelfth book of his treatise on the Soul. For we must not take this impression to resemble that made by a seal, since it is impossible to conceive that there should be many impressions made at the same time on the same thing. But φαντασία is understood to be that which is impressed, and formed, and imprinted by a real object, according to a real object, in such a way as it could not be by any other than a real object; and, according to their ideas of the φαντασίαι, some are sensible, and some are not. Those they call sensible, which are derived by us from some one or more senses; and those they call not sensible, which emanate directly from the thought, as for instance, those which relate to incorporeal objects, or any others which are embraced by reason. Again, those which are sensible are produced by a real object, which imposes itself on the intelligence and compels its acquiescence; and there are also some others which are simply apparent, mere shadows, which resemble those which are produced by real objects.
Again, these φαντασίαι are divided into rational and irrational: those which are rational belong to animals capable of reason; those which are irrational to animals destitute of reason. Those which are rational are thoughts; those which are irrational have no name, but are again subdivided into artificial and not artificial. At all events, an image is contemplated in a different light by a man skillful in art, from that in which it is viewed by a man ignorant of art.
By sensation, the Stoics understand a species of breath which proceeds from the dominant portion of the soul to the senses, whether it be a sensible perception, or an organic disposition, which, according to the notions of some of them, is crippled and vicious. They also call sensation the energy, or active exercise, of the sense. According to them, it is to sensation that we owe our comprehension of white and black, and rough and smooth: from reason, that we derive the notions which result from a demonstration, those for instance which have for their object the existence of Gods, and of Divine Providence. For all our thoughts are formed either by indirect perception, or by similarity, or analogy, or transposition, or combination, or opposition. By a direct perception, we perceive those things which are the objects of sense; by similarity, those which start from some point present to our senses, as for instance we form an idea of Socrates from his likeness. We draw our conclusions by analogy, adopting either an increased idea of the thing, as of Tityus, or the Cyclops; or a diminished idea, as of a pygmy. So, too, the idea of the center of the world was one derived by analogy from what we perceived to be the case of the smaller spheres. We use transposition when we fancy eyes in a man’s breast; combination, when we take in the idea of a Centaur; opposition, when we turn our thoughts to death. Some ideas we also derive from comparison, for instance, from a comparison of words and places.
There is also nature; as by nature we comprehend what is just and good. And privation, when for instance, we form a notion of a man without hands. Such are the doctrines of the Stoics on the subject of phantasia, and sensation, and thought.
They say that the proper criterion of truth is the comprehension, φαντασία; that is to say, one which is derived from a real object, as Chrysippus asserts in the twelfth book of his Physics; and he is followed by Antipater and Apollodorus. For Boethus leaves a great many criteria, such as intellect, sensation, appetite, and knowledge; but Chrysippus dissents from his view, and in the first book of his treatise on Reason, says that sensation and preconception are the only criteria. And preconception is, according to him, a comprehensive physical notion of general principles. But others of the earlier Stoics admit right reason as one criterion of the truth; for instance, this is the opinion of Posidonius, and is advanced by him in his essay on Criteria.
On the subject of logical speculation, there appears to be a great unanimity among the greater part of the Stoics, in beginning with the topic of the voice. Now voice is a percussion of the air; or, as Diogenes the Babylonian defines it in his essay on the Voice, a sensation peculiar to the hearing. The voice of a beast is a mere percussion of the air by some impetus: but the voice of a man is articulate, and is emitted by intellect, as Diogenes lays it down, and is not brought to perfection in a shorter period than fourteen years. And the voice is a body according to the Stoics; for so it is laid down by Archedemus in his book on the Voice, and by Diogenes, and Antipater, and also by Chrysippus in the second volume of his Physics. For everything which makes anything is a body; and the voice makes something when it proceeds to those who hear from those who speak.
A word (λέξις), again, is, according to Diogenes, a voice consisting of letters, as “Day.” A sentence (λόγος) is a significant voice, sent out by the intellect, as for instance, “It is day;” but dialect is a peculiar style imprinted on the utterance of nations, according to their race; and causes varieties in the Greek language, being a sort of local habit, as for instance the Attics say θάλαττα and the Ionians say ἡμέρη. The elements of words are the twenty-four letters; and the word letter is used in a triple division of sense, meaning the element itself, the graphical sign of the element, and the name, as “Alpha.” There are seven vowels, α, ε, η, ι, ο, υ, ω; six mutes, β, γ, δ, κ, π, τ. But voice is different from a word, because voice is a sound; but a word is an articulate sound. And a word differs from a sentence, because a sentence is always significative of something, but a word by itself has no signification, as for instance, βλίτρι. But this is not the case with a sentence. Again, there is a difference between speaking and pronouncing; the sounds are pronounced, but what are spoken are things which are capable of being spoken of.
Now of sentences there are five parts, as Diogenes tells us in his treatise on Voice; and he is followed by Chrysippus. There is the noun, the common noun, the verb, the conjunction, and the article. Antipater adds also quality, in his treatise upon Words and the things expressed by them. And a common noun (προσηγορία) is, according to Diogenes, a part of a sentence signifying a common quality, as for instance: man, horse. But a noun is a part of a sentence signifying a peculiar quality, such as Diogenes, Socrates. A verb is a part of a sentence signifying an uncombined categorem, as Diogenes (ὁ Διογένης) or, as others define it, an element of a sentence, devoid of case, signifying something compound in reference to some person or persons, as, “I write,” “I say.” A conjunction is a part of a sentence destitute of case, uniting the divisions of the sentence. An article is an element of a sentence, having cases, defining the genders of nouns and their numbers, as ὁ, ἡ, τὸ, οἱ, αἱ, τὰ.
The excellences of a sentence are five: good Greek, clearness, conciseness, suitableness, elegance. Good Greek (Ἑλληνισμὸς) is a correct style, according to art, keeping aloof from any vulgar form of expression; clearness is a style which states that which is conceived in the mind in such a way that it is easily known; conciseness is a style which embraces all that is necessary to the clear explanation of the subject under discussion; suitableness is a style suited to the subject; elegance is a style which avoids all peculiarity of expression. Of the vices of a sentence, on the other hand, barbarism is a use of words contrary to that in vogue among the well-educated Greeks; solecism is a sentence incongruously put together.
A poetical expression is, as Posidonius defines it in his introduction on Style, “A metrical or rhythmical diction, proceeding in preparation, and avoiding all resemblance to prose.” For instance, “The vast and boundless earth,” “Th’ expanse of heaven,” are rhythmical expressions; and poetry is a collection of poetical expressions signifying something, containing an imitation of divine and human beings.
A definition is, as Antipater explains it in the first book of his treatise on Definitions, a sentence proceeding by analysis enunciated in such a way as to give a complete idea; or, as Chrysippus says in his treatise on Definitions, it is the explanation of an idea. Description is a sentence which, in a figurative manner, brings one to a knowledge of the subject, or it may be called a simpler kind of definition, expressing the power of a definition in plainer language. Genus is a comprehending of many ideas indissolubly connected, as “animal;” for this one expression comprehends all particular kinds of animals. An idea is an imagination of the mind which does not express actually anything real, or any quality, but only a quasi-reality and a quasi-quality; such, for instance, is the idea of a horse when a horse is not present. Species is that which is comprehended under genus, as man is comprehended under animal.
Again, that is the most general genus which, being a genus itself, has no other genus, as “the existent.” And that is the most special species, which being a species has no other species, as, for instance, “Socrates.”
The division of genus is a dissection of it into the proximate species; as, for instance, “Of animals, some are rational, others irrational.” Contrary division is the dissection of genus into species on the principle of the contrary, so as to be by a sort of negation; as, for instance, “Of existent things, some are good and some not good;” and, “Of things which are not good, some are bad and some indifferent.” Partition is an arrangement of a genus with reference to place, as Crinis says, for instance, “Of goods, some have reference to the mind and some to the body.”
Ambiguity (ἀμφιβολία) is an expression signifying two or more things having an ordinary or a peculiar meaning, according to the pronunciation, in such a way that more things than one may be understood by the very same expression. Take, for instance, the words αὐλητρὶς πέπτωκε. For you may understand by them, a house has fallen down three times (αὐλὴ τρὶς πέπτωκε), or, a female flute-player has fallen, taking αὐλητρὶς as synonymous with αὐλητρία.
Dialectics are, as Posidonius explains them, the science of what is true and false, and neither one or the other, and it is, as Chrysippus explains it, conversant about words that signify and things that are signified; these then are the doctrines asserted by the Stoics in their speculations on the subject of the voice.
But in that part of dialectics which concerns things and ideas signified, they treat of propositions, of perfect enunciations, of judgments, of syllogisms, of imperfect enunciations, of attributes and deficiencies, and of both direct and indirect categorems or predicaments.
And they say that enunciation is the manifestation of the ideal perception; and these enunciations the Stoics pronounce some to be perfect in themselves, and some to be defective; now those are defective which furnish an incomplete sense, as for instance “He writes.” For then we ask further, “Who writes?” But those are perfect in themselves which give a sense entirely complete, as for instance “Socrates writes.” Accordingly, in the defective enunciations, categorems are applied; but in those which are perfect in themselves, axioms, and syllogisms, and questions, and interrogations, are brought into play. Now a categorem is something which is predicated of something else, being either a thing which is added to one or more objects, according to the definition of Apollodorus, or else a defective enunciation added to the nominative case, for the purpose of forming a proposition.