The stupidest person can perceive the use of money when it is explained in this way. It is difficult to make a direct comparison between various things, for instance, between cloth and corn; but when we find a common measure, in money, it is easy for the manufacturer and the farmer to estimate the value of the goods they wish to exchange in terms of this common measure. If a given quantity of cloth is worth a given some of money, and a given quantity of corn is worth the same sum of money, then the seller, receiving the corn in exchange for his cloth, makes a fair bargain. Thus by means of money it becomes possible to compare the values of goods of various kinds. Be content with this, and do not touch upon the moral effects of this institution. In everything you must show clearly the use before the abuse. If you attempt to teach children how the sign has led to the neglect of the thing signified, how money is the source of all the false ideas of society, how countries rich in silver must be poor in everything else, you will be treating these children as philosophers, and not only as philosophers but as wise men, for you are professing to teach them what very few philosophers have grasped. What a wealth of interesting objects, towards which the curiosity of our pupil may be directed without ever quitting the real and material relations he can understand, and without permitting the formation of a single idea beyond his grasp! The teacher's art consists in this: To turn the child's attention from trivial details and to guide his thoughts continually towards relations of importance which he will one day need to know, that he may judge rightly of good and evil in human society. The teacher must be able to adapt the conversation with which he amuses his pupil to the turn already given to his mind. A problem which another child would never heed will torment Emile half a year.