CHAPTER XI.

CANONS FOR ISOLATING FACTS OF CAUSATION.

It is one task of Science, amid the crowd of phenomena, to distinguish between the coexistences and successions that are accidental and those that rest upon real relations. For it is only by such knowledge that man can live among the terrific forces of nature and can make them the servants of his will. There are many groups of phenomena of which it may be known that when one is present, the others are present also. They are permanent coexistences. There are many events of which it may be known that when one has happened, the other or the others will be sure to follow. There is said to be a relation of causation between them. We have already, at great length, discussed the word cause. An event is the reaction of certain substances and energies in a certain collocation. The reaction by which this collocation arose, or any previous reaction in the long line of history, is an historical cause of the event. This total of things, including the collocation, which is their mutual relation in space, and including their history in time, may be called the Comprehensive Cause of the event, and also of the things in their states after the event.

Events are the actions of things. But every action is a reaction. This is a primary induction which men were long in making. The law of inertia, that every body remains in its state of rest or motion until acted

upon, is a subordinate generalization: the wider law is that it takes at least two to make, not only a bargain. or a quarrel, but anything. This is often what is understood to be meant by the law of causation; and it seems to be regarded as intuitively known. But it is really an induction.

If we can isolate two things so that we are sure that no third is present, and if then an event occurs, we are sure that it is a reaction between those two things. When a bit of glowing iron is lowered into a jar of oxygen and vivid combustion follows, we are sure that the iron and the oxygen are reacting; those two things are the sole material causes of the event. When a feather and a gold coin are supported in an exhausted receiver and then by the turn of a screw are left unsupported, we know that they are free from all particular influences and are reacting with the general mass of things as a whole: the fall therefore is caused by that reaction alone. This general reaction is called gravitation.

It is plain that the presence of a third thing destroys the isolation and leaves us in doubt. The combustion of a bit of iron in common air, where nitrogen is present, could not be known, without investigation, to be a reaction of the iron and oxygen alone. It might be a mutual reaction of all three or a reaction of the iron and the nitrogen. But so crowded is the world with things, and so multitudinous are their reactions, that it is a rare good fortune to be able mechanically to separate a pair or a group of reagents. What cannot be done physically must be done in thought. We must make a mental elimination, or

perhaps a series of eliminations, and thus discover the various reagents that enter into the comprehensive cause of any event that may be in question. These eliminations are made in thought by the process of subtraction.

CANON FIRST.

FOR ISOLATING FACTS OF CAUSATION BY THE TEST OF

DIFFERENCE.

In any two instances, the circumstances which are not common are the causes of the events which are not

common.

This brief and general language requires explanation. By an instance is meant any group of phenomena which may be under investigation. By a circumstance is meant a substance, an energy, a will, a collocation, or a previous event. Consequently the cause discovered may be the material cause, the energetic cause, the conditional cause, the volitional cause, or the historical cause the mere occurrence of the possibility of the reaction of the efficient causes. What is discovered is far more likely to be merely one factor of one of these causes than to be the whole of it; therefore, to avoid the tediousness of constantly saying "at least a part of one of the causes," we will adopt the name Empirical Cause. The circumstance discovered by this method is what ordinary experience leads unscientific people to speak of as the cause; and this crude use of experience is what is called empiricism.

The validity of this canon is obvious. Since events are the reactions of things, whatever is different in the

events must come from differences in the things, or in their collocations, which afford the possibilities of reaction. But differences in collocation arise through events. Thus the whole of the differences in two groups of phenomena must be accounted for by the things, their collocations, and their history. Let us consider a concrete example. In a dark room some

one touches a button, and immediately a brilliant illumination follows. There are here two instances, the room in darkness and the room illuminated. Viewed historically, the difference in circumstances is that the one instance includes the previous event of the touch of the button and the other does not. The touch of the button is therefore the historical cause of the illumination. But leaving out of view the history, it will be found that the two instances differ in the collocation of things. In the one case materials are so disposed that there is no continuous circuit for the electricity and in the other case there is a continuous circuit. Here is found the conditional cause. Further, the two instances differ, in that in one the electricity passes and in the other it does not; hence we discover the energetic cause, which is the electricity. By thus confining the attention successively to the history, the materials, the energy, or the conditions, the several kinds of cause may be elicited.

Under this canon four cases may arise:

Case 1. On striking the balance between circumstances and events in the two instances, a single circumstance and a single event may be left, not common to both instances. If so, that circumstance is manifestly the empirical cause of that event. If, for

example, into a glass containing some dilute sulphuric acid a few bits of marble be dropped, vigorous ebullition will ensue. The glass containing the acid, as it was before the dropping in of the marble, constitutes one instance; the same glass containing the marble in addition to the acid constitutes the second instance. Historically viewed, the only difference is that the one instance includes the previous event of the dropping in of the bits of marble; this therefore is the historical cause. But viewed materially, the sole difference is in the bits of marble, which were absent at first and afterwards present. The marble is therefore the material cause of the ebullition. But it is only the empirical material cause; it is not the comprehensive material cause, for in that the acid is as important a factor as the marble. When there are a number of things present and a new factor is introduced, we cannot tell by a single application of the canon how many of them co-operate with that new factor in a new comprehensive cause.

Case 2. On striking the balance, a group of circumstances and a group of events may be left not common to the two instances. If so, those circumstances are the empirical causes of those events, but which are the causes of which, can be ascertained only by a further application of the canon to simpler instances. For example, Daniel Webster left the paternal farm and, after spending four years in Dartmouth College, graduated as an accomplished orator. The two instances are Webster without education and without eloquence, and Webster after his college education, delivering some eloquent oration. The two instances