Institutio Oratoria

Such in the main are the views about proof which I have either heard from others or learned by experience. I would not venture to assert that this is all there is to be said; indeed I would exhort students to make further researches on the subject, for I admit the possibilities of making further discoveries. Still anything that may be discovered will not differ greatly from what I have said here.

I will now proceed to make a few remarks as to how proofs should be employed.

It has generally been laid down that an argument to be effective must be based on certainty; for it is obviously impossible to prove what is doubtful by what is no less doubtful. Still some things which are adduced as proof require proof themselves.

You killed your husband, for you were an adulteress.

[*](cp. v. xi. 39. ) Adultery must first be proved: once that is certain it can be used as an argument to prove what is uncertain.

Your javelin was found in the body of the murdered man.

He denies that it was his. If this point is to serve as a proof, it must itself be proved. It is,

however, necessary in this connection to point out that there are no stronger proofs than those in which uncertainty has been converted into certainty.

You committed the murder, for your clothes were stained with blood.

'This argument is not so strong if the accused admits that his clothes were bloodstained as if the fact is proved against his denial. For if he admits it, there are still a number of ways in which the blood could have got on to his clothes: if on the other hand he denies it, lie makes his whole case turn on this point, and if his contention is disproved, he will he unable to make a stand on any subsequent ground. For it will be thought that he would never have told a lie in denying the allegation, unless he had felt it a hopeless task to justify himself if he admitted it.

In insisting on our strongest arguments we must take them singly, whereas our weaker arguments should be massed together: for it is undesirable that those arguments which are strong in themselves should have their force obscured by the

surrounding matter, since it is important to show their true nature: on the other hand arguments which are naturally weak will receive mutual support if grouped together.