"It is not infrequent to see a mind of real capacity fall into error, where an intelligence of mediocre caliber asserts its efficiency. Indifference is the most serious obstacle to the attainment of judgment.
"Common sense demands a keen alertness of understanding, placed at the disposal of a reflection which appears at times slow of action, but which is long in being manifested only because of the desire to surround itself by all the guaranties of truth concerning the object in question.
"The fifth blade of the fan is the quality of deduction—the most solid basis for the judgments which are formed by common sense.
"By deduction we are able to solve all relative questions with perfect accuracy.
"It is by abstracting reckless contingencies, and by relying only upon the relativeness of facts, that we can succeed in discovering the truth that there are too many representations as to these facts.
"Deduction is the great support of mental weakness. It helps in discerning proportions, possibilities, even as it helps in skilfully avoiding the fear of error."
We shall have occasion to speak more at length of deduction, for Yoritomo devotes many pages to it. We shall, then, defer to a future chapter the interesting developments that he discloses on this subject, and we shall continue to study the fan of common sense with him.
"Foresight," he continues, "is rightly looked upon as one of the indispensable elements in cultivating common sense.
"The faculty of foresight always accompanies common sense, in order to strengthen its qualities of skill and observation.
"One must not confound, as many people are tempted to do, foresight and conjecture.