POWER OF DEDUCTION
From: Common Sense How To Exercise It
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
"In order that deductions may be a natural development, the element
relating to those which should be the object of judgment should be
"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.
"These facts should be drawn from the domain of the past; by comparison,
they can be brought to the domain of the present in order to be able to
associate the former phenomena with those from which it is a question of
"It is rarely that these latter depend on one decision alone, even when
they are presented under the form of a single negation or affirmation.
"Deduction is always the result of many observations, formulated with
great exactness, which common sense binds together.
"That which is called a line of action is always suggested by the
analysis of the events which were produced under circumstances analogous
to those which exist now.
"From the result of these observations, the habit of thinking permits of
drawing deductions and common sense concludes the analysis.
"The method of deduction rests upon this.
"One thing being equal to a previous one should produce the same effects.
"If we find ourselves faced by an incident that our memory can assimilate
with another incident of the same kind, we must deduce the following
chain of reasoning:
"First, the incident of long ago has entailed inevitable consequences.
"Secondly, the incident of to-day ought to produce the same effects,
unless the circumstances which surround it are different.
"It is then a question of analyzing the circumstances and of weighing the
causes whose manifestation could determine a disparity in the results.
"We shall interest ourselves first in the surroundings for thus, as we
have said, habits of thought and feeling vary according to the epoch and
"A comparison will be established between persons or things, in order to
be absolutely convinced of their degree of conformity.
"The state of mind in which we were when the previous events were
manifested will be considered, and we shall not fail to ascertain
plainly the similarity or change of humor at the moment as related to
that of the past.
"It is also of importance to observe the state of health, for under the
affliction of sickness things assume very easily a hostile aspect.
"It would be wrong to attribute to events judged during an illness the
same value which is given to them at this present moment.
"When one is absolutely decided as to the relation of new perceptions and
mental representations, one can calculate exactly the degree of
"The moment will then have arrived to synthesize all the observations and
to draw from them the following deductions:
"First, like causes ought, all things being equal, to produce like
"Secondly, the event which is in question will therefore have the same
consequences as the previous one, since it is presented under the same
"Being granted the principle that like causes produce like effects, as I
have just affirmed, and that there exist certain incompatibilities
between the contingencies of the past and those of to-day, one must allow
that these incompatibilities will produce different results.
"And, after this reasoning, the deductions will be established by
constituting a comparison in favor of either the present or past state
But the philosopher, who thinks of everything, has foreseen the case
where false ideas have obscured the clearness of the deductions, and he
said to us:
"The association of false ideas, if it does not proceed from the
difficulty of controlling things, is always in ungovernable opposition to
the veracity of the deduction.
"What would be thought of a man of eighty years who, coming back to
his country after a long absence, said, on seeing the family roof from
"'When I was twenty years old, in leaving here, it took me twenty
minutes to reach the home of my parents, so I shall reach the threshold
in twenty minutes.'
"The facts would be exact in principle.
"The distance to be covered would be the same; but legs of eighty
years have not the same agility as those of very young people, and in
predicting that he will reach the end of his walk in the same number
of minutes as he did in the past, the old man would deceive himself
"If, on the contrary, on reaching the same place he perceived that a new
route had been made, and that instead of a roundabout way of approach, as
in the past, the house was now in a straight line from the point where he
was looking at it, it would be possible to estimate approximately the
number of minutes which he could gain on the time employed in the past,
by calculating the delay imposed upon him by his age and his infirmities.
"Those to whom deduction is familiar, at times astonish thoughtless
persons by the soundness of their judgment.
"A prince drove to his home in the country in a sumptuous equipage.
"He was preceded by a herald and borne in a palanquin by four servants,
who were replaced by others at the first signs of fatigue, in order that
the speed of the journey should never be slackened.
"As they were mounting, with great difficulty, a zigzag road which led up
along the side of a hill, one of these men cried out:
"'Stop,' said he, 'in the name of Buddha, stop!'
"The prince leaned out from the palanquin to ask the cause of this
"'My lord,' cried the man, 'if you care to live, tell your porters to
"The great man shrugged his shoulders and turning toward his master of
ceremonies, who was riding at his side, said:
"'See what that man wants.'
"But scarcely had the officer allowed his horse to take a few steps in
the direction of the man who had given warning when the palanquin, with
the prince and his bearers, rolled down a precipice, opened by the
sinking in of the earth.
"They raised them all up very much hurt, and the first action of the
prince, who was injured, was to have arrested the one who, according to
him, had evoked an evil fate.
"He was led, then and there, to the nearest village and put into a cell.
"The poor man protested.
"'I have only done what was natural,' said he. 'I am going to explain it,
but I pray you let me see the prince; I shall not be able to justify
myself when he is ill with fever.'
"'What do you mean,' they replied, 'do you prophesy that the prince will
have a fever?'
"'He is going to have it.'
"'You see, you are a sorcerer,' said the jailer, 'you make predictions.'
"And then he shut him in prison, to go away and to relate his
conversation to them all.
"During this time, they called in a healer who stated that the wounds of
the great nobleman were not mortal in themselves, but that the fever
which had declared itself could become dangerous.
"He was cured after long months.
"During this time the poor man languished in his prison, from whence he
was only taken to appear before the judges.
"Accused of sorcery and of using black magic, he explained very simply
that he had foreseen the danger, because in raising his eyes he had
noticed that the part of the ground over which the herald had passed was
sinking, and that he had drawn the following conclusions:
"The earth seemed to have only a medium thickness.
"Under the feet of the herald he had seen it crumble and fall in.
"He had deduced from this that a weight five times as heavy added to that
of the palanquin, would not fail to produce a landslide.
"As to the prediction concerning the fever, it was based on what he had
seen when in the war.
"He had then observed that every wound is always followed by a
disposition to fever; he therefore could not fail to deduce that the
serious contusions occasioned by the fall of the prince would produce the
"The judge was very much imprest with the perspicacity of this man; not
only did he give him his liberty, but he engaged him in his personal
service and in due time enabled him to make his fortune."
We do not wish to affirm--any more than Yoritomo, for that matter--that
fortunate deductions are always so magnificently rewarded as were those
of this man.
However, without the causes being so striking, many people have owed
their fortune to the faculty which they possest of deducing results
where the analogy of the past circumstances suggested to them what
He warns us against the propensity which we have of too easily avoiding a
conclusion which does not accord with our desires.
"Too many people," said he, "wish to undertake to make deductions by
eliminating the elements which deprive them of a desired decision.
"They do not fail either to exaggerate the reasons which plead in favor
of this decision; also we see many persons suffer from reasoning, instead
of feeling the good effects of it."
Those who cultivate common sense will never fall into this error, for
they will have no difficulty in convincing themselves that by acting thus
they do not deceive any one except themselves.
By glossing over truth in order to weaken the logical consequences of
deductions they are the first to be the victims of this childish trick.
That which is called false deduction is rarely aught save the desire to
escape a resolution which a just appraisement would not fail to dictate.
It might be, also, that this twisting of judgment comes from a person
having been, in some past time, subjected to unfortunate influences.
By devoting oneself to the evolution of thought, of which we have already
spoken when presenting the symbolical fan, and above all, by adopting the
precepts which, following the method of Yoritomo, we are going to develop
in the following lessons, we shall certainly succeed in checking the
errors of false reasoning.
"The important thing," said he, "is not to let wander the thought, which,
after resting for a moment on the subject with which we are concerned and
after touching lightly on ideas of a similar character, begins to stray
very far from its basic principles.
"Have you noted the flight of certain birds?
"They commence by gathering at one point, then they describe a series of
circles around this point, at first very small, but whose circumference
enlarges at every sweep.
"Little by little the central point is abandoned, they no longer approach
it, and disappear in the sky, drawn by their fancy toward another point
which they will leave very soon.
"The thoughts of one who does not know how to gather them together and to
concentrate them are like these birds.
"They start from a central point, then spread out, at first without
getting far from this center, but soon they lose sight of it and fly
toward a totally different subject that a mental representation has
"And this lasts until the moment when, in a sudden movement, the first
one is conscious of this wandering tendency.
"But it is often too late to bring back these wanderers to the initial
idea, for, in the course of their circuits, they have brushed against a
hundred others, which are confounded with the first, weaken it, and take
away its exact proportions.
"The great stumbling-block again is that of becoming lost in the details
whose multiplicity prevents us from discerning their complete function in
the act of practising deduction.
"It is better, in the case where our perception finds itself assailed by
the multitude of these details, to proceed by the process of elimination,
in order not to become involved in useless and lazy efforts.
"In this case we must act like a man who must determine the color of a
material at a distance where the tiny designs stand out in a relief of
white on a background of black.
"Suppose that he is placed at a distance too great to perceive
"What should he do to be able to give the best possible description?
"He will proceed by elimination.
"The material is neither red nor green; orange and violet must be set
aside, as well as all the subordinate shades.
"It has a dull appearance, hence, it is gray; unless.... And here mental
activity comes into play and will suggest to him that gray is composed of
black and white.
"He will then be sure to form a judgment which will not be spoiled
by falsity, if he declares that the material is a mixture of black
"Later, by drawing nearer, he will be able to analyze the designs and to
convince himself of their respective form and color, but by deducing that
the material was made up of the mixture of two colors he will have come
as near as possible to the truth:
"Deduction never prejudges; it is based on facts; only on things
accomplished; it unfolds the teaching that we ought to obtain as a
Again the Shogun recommends to us the union of thoughts and the
continuous examination of past incidents in the practise of deductions.
"If on entering a room," said he, "we are at times confused, it happens
also that we correct this impression after a more attentive examination.
"The gilding is of inferior quality; the materials are of cotton, the
paintings ordinary, and the mattings coarse.
"At first sight we should have deduced, judging from appearances, that
the possessor of this house was a very rich man, but a second examination
will cause us to discover embarrassment and anxiety.
"It is the same with all decisions that we must make.
"Before devoting ourselves to deductions inspired by the general aspect
of things, it is well to examine them one by one and to discover their
defects or recognize their good qualities.
"We shall be able thus to acquire that penetration of mind whose
development, by leading us toward wise deductions, will bring us to the
discovery of the truth."
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