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8 SIGNS, COMMONPLACES, AND ALLUSIONS For their part, the practitioners of political argument might accept with some equanimity that their proofs were not conducted in the geometrical manner— except that if they wanted to counter, and not just to ignore, the potential criticisms of a Plato or an Aristotle, they had better be in a position to give some account of the criteria by which those proofs of theirs were to be evaluated. G. E. R. Lloyd, Demystifying Mentalities In his Nicomachean Ethics, Aristotle famously observes that to demand strict logical proof from a rhetorician is as foolish as accepting the arts of persuasion from a mathematician (I.3: 1094b25).This reflects his appreciation of the different methods involved in scientific inquiry and the practical questions of human behavior and character.1 As we have seen, the Sophists fit largely into the practical side of the equation, and the modes of proof they employed differ accordingly. MODES OF PROOF These modes receive a more generally technical aspect underAristotle’s direction in the Rhetoric, but as we have seen on several occasions,Aristotle is dealing with strategies that he inherits from others who had already recognized their utility.Two of these that will be discussed in this chapter are the distinction between necessary and nonnecessary signs and topoi or commonplaces. Aristotle notes that few of the premises from which rhetorical syllogisms (or reasoning) are formed are necessarily true; the premises from which enthymemes are spoken are less than necessarily true, and enthymemes are derived from eikota and signs (sēmeia).2 These signs are called tekmēria if they are necessary, but if they are not necessary they have no distinguishing name (Rhet. I.2: 1357b).And again, he tells us, dialectical and rhetorical syllogisms are those in which we state topoi, which may be held in common to questions of many different species of knowledge.The topos of the more or the less, for example, can apply to justice as much as it applies to physics (I.2.21: 1358a). 114 Sophistic Strategies of Argumentation How exactly Aristotle intended the term topos to be understood is still a matter of debate.We will consider this in the discussions that follow. ARGUING FROM SIGNS A central characteristic of rhetorical argumentation is the way in which it anticipates the responses of the audience in the structure of the argument, inviting a codevelopment through expressed and implicit commonalities. Strategies of invitation include ways to capture the audience’s prior beliefs and understandings, to expand the cognitive environment of the argumentation in relevant ways.We have seen the important role that eikos arguments played in such argumentation. But in exploring some of the examples set out in chapter 5, it may have occurred to us that some of the likelihoods identified there depended on the commonality of certain indications or signs. That is, one thing is taken as an indication of something else, and where this is used in an argument, it serves as evidence for a conclusion. In the first of Antiphon’s tetralogies, for example, the fact that the victims (master and slave) were still wearing their cloaks is taken as a sign that the culprits were not professional killers.The defendant does not contest the quality of the sign but simply counters that the assailants did not have time to strip the clothes from their victims. In On the Murder of Herodes, the absence of any bloodstains (nor any other sēmeion) is taken by the defendant as a sign against the prosecution’s claim that the victim met his death on land and had been hit on the head with a stone. One of the very short fragments relating to Antiphon explains that in a lost work called the Art he “says that past events are confirmed by signs (sēmeia), future events foreshadowed by tekmēria” (DK 87B: 163). Certainly this is how sēmeia are employed in the speeches that have come down to us. DouglasWalton (2006, 112) identifies the argument from sign as a defeasible argument that employs a generalization that is not absolute. Some generalizations attribute a property to every member of a group and thus are absolute. But other generalizations are inductive and tell us what happens in most or a percentage of cases, and still others are defeasible in that they tell us that a group ‘generally’ has a property.‘Birds fly’ is such a defeasible generalization ; it tells...

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