The third kind of proof, which is drawn into the service of the case from without, is styled a παράδειγμα by the Greeks, who apply the term to all comparisons of like with like, but more especially to historical parallels. Roman writers have for the most part preferred to give the name of comparison to that which the Greeks style παραβολή, while they translate παράδειγμα by example, although this latter involves comparison, while the former is of the nature of an example.

For my own part, I prefer with a view to making my purpose easier of apprehension to regard both as παραδείγματα and to call them examples. Nor am I afraid of being thought to disagree with Cicero, although he does separate comparison from example. de Inv. I. xxx. 49. For he divides all arguments into two classes, induction and ratiocination, just as most Greeks cp. Ar. ah. I. ii. 18. divide it into παραδείγματα and ἐπιχειρήματα, explaining παράδειγμα as a rhetorical induction.

The method of argument chiefly used by Socrates was of this nature: when he had asked a number of questions to which his adversary could only agree, he finally inferred the conclusion of the problem under discussion from its resemblance to the points already conceded. This method is known as induction, and though it cannot be used in a set speech, it is usual in a speech to assume that which takes the form of a question in dialogue.

For instance take the following question: What is the finest form of fruit? Is it not that which is best? This will be admitted. What of the horse? What is the finest? Is it not that which is the best? Several more questions of the same kind follow. Last comes the question for the sake of which all the others were put: What of man? Is not he the finest type who is best? The answer can only be in the affirmative.