Before entering the path which relates directly to the intellectual efforts concerning the acquisition of common sense, the Shogun calls our attention to the power of deduction.
"It is only," said he, "where we are sufficiently permeated with all the principles of judgment that we shall be able to think of acquiring this quality, so necessary to the harmony of life.
"The most important of all the mental operations which ought to be practised by him who desires common sense to reign supreme in all his actions and decisions, is incontestably deduction.
"When the union of ideas, which judgment permits, is made with perception and exactness, there results always an analysis, which, if practised frequently, will end by becoming almost a mechanical act.
"It is, however, well to study the phases of this analysis, in order to organize them methodically first.
"Later, when the mind shall be sufficiently drilled in this kind of gymnastics, all their movements will be repeated in an almost unconscious way, and deduction, that essential principle of common sense, will be self-imposed.
"In order that deductions may be a natural development, the element relating to those which should be the object of judgment should be grouped first.
"The association of statements is an excellent method for it introduces into thought the existence of productive agents.
"We have already spoken of the grouping of thoughts, which is a more synthetical form of that selection.
"Instead of allowing it to be enlarged by touching lightly on all that which is connected with the subject, it is a question, on the contrary, of confining it to the facts relating to only one object.