"Comparison is a mental operation which permits us to bring things that we desire to understand to a certain point. "It is comparison which has divided time according to periods, which the moon follows during its entire length. "It is by comparing their different aspects and by calculating the duration of their transformations, that men have been able to divide time as they do in all the countries of the world. "The science of numbers is also born of comparison, which has been established between the quantities that they represent. "This is the art of calculating the differences existing between each thing, by determining the relativeness of their respective proportions. "Comparison acts on the mind automatically, as a rule. "It is indispensable to the cultivation of common sense, for it furnishes the means of judging with full knowledge of all the circumstances. "Analysis is an operation, which consists of separating each detail from the whole and of examining these details separately, without losing sight of their relationship to the central element. "Analysis of the same object, while being scrupulously exact, can, however, differ materially in its application, according to the way that the object is related to this or that group of circumstances. "There are, however, immutable things. "For example: the letters of the alphabet, the elementary sounds, the colors etc., etc. "It suffices to quote only these three elements; one can easily understand that the most elaborate manuscript is composed of only a definite number of letters always repeating themselves, whose juxtaposition forms phrases, then chapters, and finally the complete work. "Music is composed only of seven sounds whose different combinations produce an infinite variety of melodies. "Elementary colors are only three in number. "All the others gravitate around them. "Therefore, these same letters, these same notes, these same colors, according to their amalgamation, can change in aspect and cooperate in the production of different effects. "The same letters can express, according to the order in which they are placed, terror or confidence, joy or grief. "The same is true of notes and colors. "Common sense ought then, considering these rules, to know how to analyze all the details and, having done this, to coordinate and to classify them, in order to distinguish them easily. "Coordination and classification form an integral part of common sense." And Yoritomo, who delights in reducing the most complex questions to examples of the rarest simplicity, says to us: "I am supposing that one person says to another, I have just met a negro. The interlocutor, as well as he who mechanically registers this fact, without thinking, gives himself up to analysis and to coordination which always precedes synthesis. "Without being aware of this mental action, their minds will be occupied first with the operations of perception then of classification.