And the source of all confirmations has been already explained as occasion offered, and has been demonstrated no less clearly than the nature of the case required.  But how each separate statement, and each part of a statement, and every dispute ought to be handled,—­whether we refer to verbal discussion or to writings,—­and what arguments are suitable for each kind of discussion, we will mention, speaking separately of each kind, in the second book.  At present we have only dropped hints about the numbers, and moods, and parts of arguing in an irregular and promiscuous manner; hereafter we will digest (making careful distinctions between and selections from each kind of cause) what is suitable for each kind of discussion, culling it out of this abundance which we have already displayed.

And indeed every sort of argument can be discovered from among these topics; and that, when discovered, it should be embellished, and separated in certain divisions, is very agreeable, and highly necessary, and is also a thing which has been greatly neglected by writers on this art.  Wherefore at this present time it is desirable for us to speak of that sort of instruction, in order that perfection of arguing may be added to the discovery of proper arguments.  And all this topic requires to be considered with great care and diligence, because there is not only great usefulness in this matter, but there is also extreme difficulty in giving precepts.

XXXI.  All argumentation, therefore, is to be carried on either by induction, or by ratiocination.  Induction is a manner of speaking which, by means of facts which are not doubtful, forces the assent of the person to whom it is addressed.  By which assent it causes him even to approve of some points which are doubtful, on account of their resemblance to those things to which he has assented; as in the Aeschines of Socrates, Socrates shows that Aspasia used to argue with Xenophon’s wife, and with Xenophon himself.  “Tell me, I beg of you, O you wife of Xenophon, if your neighbour has better gold than you have, whether you prefer her gold or your own?” “Hers,” says she.  “Suppose she has dresses and other ornaments suited to women, of more value than those which you have, should you prefer your own or hers?” “Hers, to be sure,” answered she.  “Come, then,” says Aspasia, “suppose she has a better husband than you have, should you then prefer your own husband or hers?” On this the woman blushed.

But Aspasia began a discourse with Xenophon himself.  “I ask you, O Xenophon,” says she, “if your neighbour has a better horse than yours is, whether you would prefer your own horse or his?” “His,” says he.  “Suppose he has a better farm than you have, which farm, I should like to know, would you prefer to possess?” “Beyond all doubt,” says he, “that which is the best.”  “Suppose he has a better wife than you have, would you prefer his wife?” And on this Xenophon himself was silent.  Then spake Aspasia,—­“Since