To test the value of direct evidence, therefore, as to single and simple facts, consider whether the evidence comes from a specifically named source, whether there is any likelihood that the witness may have been honestly deceived in his observation, whether he had a good opportunity to know the facts and a sufficient knowledge of the subject about which he is giving evidence, and, finally, whether he was reasonably free from bias in the matter.

Whenever you use direct evidence, however, it must be direct.  To assert that “every one knows that secret societies in a certain school have led to immoral practices,” is not direct evidence, nor to declare that “the best authorities in the city are agreed that the company should lay double tracks on a certain street.”  Such assertions are apt to be the most roundabout sort of hearsay.  Try cross-examining the next man you hear make this kind of sweeping assertion, in order to see what he really knows of the facts, and you will soon find how recklessly such assertions are made.  You constantly hear grave statements of facts whose ultimate basis is the imagination of some enterprising newspaper reporter; yet careful and truthful people pass them on as if they were indubitable.

The news columns of the papers are largely written by young fellows just out of high school, who will declare the whole gospel on subjects with which they have a half hour’s acquaintance, yet most people never question their statements.  The printed page, whether of a hook, a magazine, or a newspaper, casts a spell on our judgment.  Such floating assertions, with no one to father them, are of no value whatever.  If you have to use statements in a newspaper as direct evidence, either take them from a newspaper which is recognized as careful about facts, or else look up the matter in two or three papers, and show that their testimony agrees.

On the other hand, a specific name, with a specific reference to volume and page, will go a long way to give your readers confidence in the evidence you adduce.  And rightly so, for one man with a name and address is worth hundreds of unnamed “highest authorities”; and the more specifically you refer to him and to his evidence, the more likely you will be to win over your audience to your view.

A famous and effective example of the use of specific names to give authority to an argument, and the incidental refutation of a vague and loose assertion, is found in Lincoln’s address at Cooper Institute, in the first part of which he took up Senator Douglas’s statement that “our fathers, when they framed the government under which we live, understood this question just as well as, and even better than, we do now,” with the implication that they intended to forbid the federal government to control slavery in the federal territories.  Lincoln showed that “our fathers who framed the government under which we live” must be the makers of the Constitution:  and then he proceeded to show just what action each one of them, so far as record had been preserved, had taken on the question.  Here is a passage from his argument: