here introduced merely to illustrate that no point in controversy in a matter of this character can be definitely settled by the unsupported testimony of a single honest witness relying upon his memory after the lapse of many years. Evidence such as we are to consider is of two kinds, known in logic as _a priori_ and _a posteriori_. The first kind is evidence from antecedent probability; the second is evidence relating to matter after the fact. An illustration will serve: A man is found dead, with a wound in his forehead, and there are no witnesses who can be produced in court who saw the man die. The wound appears to have been produced by a bullet, and, as no weapon is found beside the body, there is a presumption that the man has been murdered. A neighbor is accused of having committed the deed. The _a priori_ evidence is adduced in testimony that the defendant and the deceased had long been on bad terms with each other on account of a line fence between their adjacent properties; that the defendant had threatened to kill the deceased and had recently bought a revolver. The evidence _a posteriori_ is found in the fact that the defendant's revolver on examination shows one empty chamber and that the ball in the deceased man's brain is of the caliber suited to his weapon and of the same manufacture as the unused cartridges in the weapon. To this may be added other incriminating facts, as of measured footprints near the scene of murder which correspond to the size of the defendant's boots, and of possible blood stains upon his clothing. A very large volume of _a priori_ evidence is sometimes set aside by a single _a posteriori_ fact; for instance, in the foregoing supposititious case it may be entirely possible to prove that the murder was committed by a tramp, and that the defendant was ten miles away at the time the deed was done. On the other hand, a large volume of _a posteriori_ evidence sometimes disappears in the face of a single _a priori_ consideration. A man is accused of having stolen a sheep. It is shown in evidence that on the evening when the sheep was stolen he walked through his neighbor's pasture and was seen to approach the sheep; that he sold mutton on the day after the loss of the sheep, and that a fresh sheepskin was found nailed to his barn door. All this _a posteriori_ evidence and much more may be completely set aside in the minds of the jury by the single fact that the man accused has lived for forty years in the community and has borne a reputation incompatible with the crime of sheep-stealing. In the examination of testimony concerning alleged utterances of Abraham Lincoln in matters of religious belief, we must ask such questions as these: