But we think that these and such as these are the common topics suitable to an argument of this description.  In the first place, a panegyric upon, and a confirmation of that writing which you are producing.  Then a comparison of the matter which is the subject of discussion, with that which is a settled case, in such a manner that the case which is under investigation may appear to resemble that about which there are settled and notorious rules.  After that, one will express admiration, (by way of comparison), how it can happen that a man who admits that this is fair, can deny that other thing, which is either more equitable still, or which rests on exactly similar principles; then, too, one will contend that the reason why there is no precise law drawn up for such a case, is because, as there was one in existence applicable to the other case, the framer of that law thought that no one could possibly entertain a doubt in this case; and afterwards it will be well to urge that there are many cases not provided for in many laws, which beyond all question were passed over merely because the rule as to them could be so easily collected out of the other cases which were provided for; and last of all, it is necessary to point out what the equity of the case requires, as is done in a plain judicial case.

But the speaker who is arguing on the other side is bound to try and invalidate the comparison instituted, which he will do if he can show that that which is compared is different from that with which it is compared in kind, in nature, in effect, in importance, in time, in situation, in character, in the opinion entertained of it; if it is shown also in what class that which is adduced by way of comparison ought to stand, and in what rank that also ought to be considered, for the sake of which the other thing is mentioned.  After that, it will be well to point out how one case differs from the other, so that it does not seem that any one ought to have the same opinion of both of them.  And if he himself also is able to have recourse to ratiocination, he must use the same ratiocination which has been already spoken of.  If he cannot, then he will declare that it is not proper to consider anything except what is written; that all laws are put in danger if comparisons are once allowed to be instituted; that there is hardly anything which does not seem somewhat like something else; that when there are many circumstances wholly dissimilar, still there are separate laws for each individual case; and that all things can be proved to be like or unlike to each other.  The common topics derived from ratiocination ought to arrive by conjecture from that which is written to that which is not written; and one may urge that no one can embrace every imaginable case in a written law, but that he frames a law best who takes care to make one thing understood from another.  One may urge, too, that in opposition to a ratiocination of this sort, conjecture is no better than a divination, and that it would be a sign of a very stupid framer of laws not to be able to provide for everything which he wished to.