But that is a decision admitting of comparisons, which in a multitude of different circumstances contains some principle which is alike in all. Its parts are three,--representation, collation, example. A Representation is a statement demonstrating some resemblance of bodies or natures; Collation is a statement comparing one thing with another, because of their likeness to one another; Example is that which confirms or invalidates a case by some authority, or by what has happened to some man, or under some especial circumstances. Instances of these things, and descriptions of them, will be given amid the precepts for oratory. 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.