While upon this subject, I may tell you a story which was related to me by a friend of mine. It is a story which the master of a certain money-changer's shop used to be very fond of telling. An important part of a money-changer's business is to distinguish between good and bad gold and silver. In the different establishments, the ways of teaching the apprentices this art vary; however, the plan adopted by the money-changer was as follows:--At first he would show them no bad silver, but would daily put before them good money only; when they had become thoroughly familiar with the sight of good money, if he stealthily put a little base coin among the good, he found that they would detect it immediately,--they saw it as plainly as you see things when you throw light on a mirror. This faculty of detecting base money at a glance was the result of having learned thoroughly to understand good money. Having once been taught in this way, the apprentices would not make a mistake about a piece of base coin during their whole lives, as I have heard. I can't vouch for the truth of this; but it is very certain that the principle, applied to moral instruction, is an excellent one,--it is a most safe mode of study. However, I was further told that if, after having thus learned to distinguish good money, a man followed some other trade for six months or a year, and gave up handling money, he would become just like any other inexperienced person, unable to distinguish the good from the base. Please reflect upon this attentively. If you once render yourself familiar with the nature of the uncorrupted heart, from that time forth you will be immediately conscious of the slightest inclination towards bias or selfishness. And why? Because the natural heart is illumined. When a man has once learned that which is perfect, he will never consent to accept that which is imperfect; but if, after having acquired this knowledge, he again keeps his natural heart at a distance, and gradually forgets to recognize that which is perfect, he finds himself in the dark again, and that he can no longer distinguish base money from good. I beg you to take care. If a man falls into bad habits, he is no longer able to perceive the difference between the good impulses of his natural heart and the evil impulses of his corrupt heart. With this benighted heart as a starting-point, he can carry out none of his intentions, and he has to lift his shoulders sighing and sighing again. A creature much to be pitied indeed! Then he loses all self-reliance, so that, although it would be better for him to hold his tongue and say nothing about it, if he is in the slightest trouble or distress, he goes and confesses the crookedness of his heart to every man he meets. What a wretched state for a man to be in! For this reason, I beg you to learn thoroughly the true silver of the heart, in order that you may make no mistake about the base coin.