The Lives and Opinions of Eminent Philosophers Diogenes Laërtius (first ebook reader .TXT) 📖

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,