Institutio Oratoria

We may also begin with the reason and then proceed to the conclusion as in another passage from the same speech [*](ib. iii. 9. ) :

But if the Twelve Tables permitted the killing of a thief by night under any circumstances, and by day if he used a weapon to defend himself, who is there who will contend that the slayer must be punished under whatever circumstances a man has been killed?

'The process is still further varied by Cicero, and the reason placed third, as in the phrase,

When he sees that the sword is sometimes placed in our hands by the laws themselves.

On the other hand, he places the various parts in the regular order in the following instance:

How can it be unjust to kill a robber who lies in wait for his victim?

[*](ib. iv. 10. ) Next comes the reason:

What is the object of our escorts and our swords?

Last comes the conclusion resulting from the major premise and the reason:

Which we certainly should not be permitted to have, if we were absolutely forbidden to use them.

This form of proof may be countered in three ways, that is to say it may be attacked in all its parts. For either the major premise or the minor or the conclusion or occasionally all three are refuted. The major premise is refuted in the following case:

I was justified in killing him, as he lay in wait for me.

For the very first question in the defence of Milo is

whether it is right that he who confesses that he has killed a man should look upon the light of day.

The minor premise is refuted by all the methods which we mentioned in dealing with refutation. [*](In the preceding chapter.) As to the reason it must be pointed out that it is sometimes true when the proposition to which it is attached is not true, but may on the other hand sometimes be false although the proposition is true. For example,

Virtue is a good thing

is true, but if the reason,

Because it brings us wealth,

be added, we shall have an instance of a true major premise and a false reason.

With regard to the conclusion, we may either deny its truth when it infers something which does not logically result from the premises, or we may treat it as irrelevant. The truth is denied in the following case:

We are justified in killing one who lies in wait for us; for since, like an enemy, he threatens us with violence, we ought to repulse his attack as though he were an enemy: therefore Milo was justified in killing Clodius as an enemy.

The conclusion is not valid, since we have not yet proved that Clodius lay in wait for him But the conclusion that we are therefore justified in killing one who lies in wait for us is perfectly true, though irrelevant to the case, for it is not yet clear that Clodius lay in wait for Milo.