Part 24

"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 the environment.

"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 comparison.

"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 effects.

"Secondly, the event which is in question will therefore have the same consequences as the previous one, since it is presented under the same conditions.

"Or again:

"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 of things."

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 a distance:

"'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 most surely.

"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: