Is the witness credible? Had he opportunity to know what he professes to relate? Were other witnesses present, and if so, do they agree in their recollection of the words spoken? Was the interview published at a time when it could have been denied by those who had knowledge of the incident? Had the witness time to enlarge the incident by frequent telling and by such exaggeration and enlargement of detail as is likely to occur with the lapse of years? Had the witness a probable motive for exaggeration; does he appear to tell what he would presumably have liked Mr. Lincoln to say, and does it sound more like the narrator's own style than it does like Mr. Lincoln? Do the language and the sentiments expressed accord with the published addresses, letters, and authentic documents of Abraham Lincoln, and are the views expressed in accord with the views which he is known to have held? On the other hand, is it possible that in the freedom of personal conversation Mr. Lincoln may have said some things which he would not have been likely to say in formal discourse or to write in official documents? It is not necessary that we formally ask these and only these questions; but these are the kinds of sieve through which oral testimony must be passed if we are to learn the truth. Particular care needs to be exercised in the application of these tests, and especially in the employment of all _a priori_ methods. The author of this volume is a Christian minister, and would be heartily glad to find in Mr. Lincoln's authentic utterances indubitable evidence that Mr. Lincoln was essentially a Christian; there is need that he take especial care not to apply these discriminating tests in such fashion as to sustain his own prejudices. Nor must he magnify his caution until it becomes an inverted prejudice. On the other hand, the _a priori_ method must on no account be ruled out. Mr. Lincoln left a great quantity of authentic material. His speeches, letters, and state papers fill twelve volumes, and even these do not contain all of his signed material. We are compelled to judge alleged utterances of his somewhat in the light of our certain knowledge of what he wrote and said. Let us illustrate the application of this principle: If an aged man living in central Illinois were now to arise and say: "I knew Abraham Lincoln, and he said to me one day in private conversation, 'There is no God,'" we should be justified in discrediting that man's testimony, even though he bore a good reputation for veracity. The antecedent improbability of such a declaration on the part of Mr. Lincoln is too great for us to accept it on the basis of one man's recollection of a private and unwitnessed conversation fifty years after Mr. Lincoln's death. We should be equally justified in rejecting the testimony at this late date of one of Mr. Lincoln's old-time neighbors who would say that Mr. Lincoln told him that he believed the whole of the Athanasian Creed.