Institutio Oratoria

It is more important for our purpose to note that arguments may be drawn from similar, opposite, and dissimilar points of law. As an example of the first, take the following passage from the Topica of Cicero, [*](iii. 15.) where he argues that a man to whom the usufruct of a house has been left will not restore it in the interests of the heir if it collapses; just as lie would not replace a slave if he should die. The following will provide an example of an argument drawn from opposite points of law:

The absence of a formal contract is no bar to the legality of a marriage, provided the parties cohabit by mutual consent, since the signing of a formal document will count for nothing in the absence of such mutual consent.

If anyone had driven me from my house by armed violence, I should have ground for action against him. Have I then no ground, if he has prevented me from entering my house?

Because a man has bequeathed all his silver to a given person and this bequest is regarded as including silver coin as well as plate, it does not follow that he intended all outstanding debts to be paid to the legatee.

Some draw a distinction between analogy and similarly, but personally I regard the former as included under the latter. For the statement that the relation of 1 to 10 is the same as that of 10 to certainly involves similarity,

just as does the statement that a bad citizen may be compared to an actual enemy. But arguments of this kind are carried still further:

If connexion with a male

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slave is disgraceful to the mistress of the house, so is the connexion of the master with a female slave. If pleasure is an end sought by dumb animals, so also must it be with men.

But these arguments may readily be met by arguments from dissimilars:

It is not the same thing for the master of the house to have intercourse with a female slave as for the mistress to have intercourse with a male slave; nor does it follow that because dumb animals pursue pleasure, reasoning beings should do likewise.

Because pleasure is an end sought by dumb animals, it should not be sought by reasoning beings.