Index

The Greek notion of probabilities is intimately tied to the practice of devising two-fold arguments, which developed into the topical system.

Corax and Tisias: Corax ("crow") was a teacher of rhetoric in Syracuse ca. 467 BCE. He offered a guarantee of success in litigation after taking his course. Tisias, his student, refused to pay his fee. In court, Tisias argued that if he won his case, he was exempt because he had won, and if he lost, he was exempt because he had failed at litigation. Corax argued that, if Tisias lost he had to pay the fee, but if he won he still had to pay because he had succeeded at litigation. The case was thrown out with the epigram "a bad egg from a bad crow." (Prolegomena sylloge No. 4, H. Rabe, Leipzig, 1931, p. 25ff.).

An example of an argument from probability. This one Aristotle attributes to Corax and claims it exemplifies "making the worse argument appear the better":

For if a man is not likely to be guilty of what he is accused of, for instance if, being weak, he is accused of assault and battery, his defence will be that the crime is not probable (e.g. is it likely that a weak man would even try to beat up a stronger man). But if he is likely to be guilty, for instance, if he is strong, it may be argued again that the crime is not probable, for the very reason that it was bound to appear so (e.g. Is it likely a strong man would beat up a weaker precisely because he would be the first to be suspected). (Rhetoric 1402a.)

An argument from probability in an editorial from the Winston-Salem Journal, 1/24/00. http://www.journalnow.com/news/local/opinion/editorials/left24a.htm.

Now what?