CHAPTER I EXPLANATION What is Explanation?-Probability, classification and the discovery of laws all have to do with facts. Probability tells us the frequency with which a fact may be expected to occur; classification puts the fact into a group of like facts, and the better the classification from a scientific point of view, the more does the placing of the particular fact tell us with regard to its relations of resemblance and difference with other facts. A law states the conditions under which a fact occurs. In which of these cases can we be said to explain a fact? The statement of the frequency with which an event occurs does not explain the event. We may say that the order of nature is such that, unless some change in the conditions is introduced, we may expect an event to occur with the same frequency in the future as it has manifested in the past; but that is obviously very far from an adequate explanation. Do we explain an event when we classify it? When we ask why a given body fell to the ground, do we explain the phenomenon by saying that it was a heavy body? Not entirely, and if we did not already know some law holding for heavy bodies, our statement would throw no light on the subject. It is quite true that a statement of this sort may be a preliminary to explanation. A law tells us how phenomena of a given sort behave; it states the conditions of their occurrence, and if we can not say what sort of thing a given fact is we can not state its conditions. In bringing a fact under a law we first approach an explanation of it. Explanation has been defined as (in positive science) "the reduction of a phenomenon to the terms of a general principle, whatever that principle may be."1 Have we reached a final and complete explanation of a fact when we have brought it under a general principle? In many cases this seems to be sufficient; if we are familiar with the law and if we can see its bearing upon the fact in question, we are ordinarily content with this sort of explanation. An eclipse of the moon is sufficiently explained for ordinary purposes if we are told that it is caused by the presence of an opaque object between it and the source of its light. Or the revolution of the moon about the earth may be explained by saying that it is the resultant of the operation of centripetal and centrifugal forces. But there are two further questions that may be asked. First, what are the circumstances in which the law operates in the present case? and second, how is the law itself to be accounted for? Let us consider the second question: How is a law to be explained? The answer is: By showing that the law is itself a case of a more general law. The attraction of the earth for bodies on its surface is explained by showing that it is a case under the law of gravitation. "It has often been found that scientific men were in possession of 1 Dictionary of Philosophy, etc. Ed. Professor J. Mark Bald SYSTEMATIZING DATA 239 several well-known laws without perceiving the bond which connected them together. Men, for instance, had long known that all heavy bodies tended to fall towards the earth, and before the time of Newton it was known to Hooke, Huyghens and others, that some force probably connected the earth with the sun and moon. It was Newton, however, who clearly brought these and many other facts under one general law, so that each fact or less general law throws light upon every other.” 2 How far can this be carried? Do we not at last arrive at laws which are elementary and not to be explained by reference to anything simpler or more fundamental? Are we then to regard these elementary laws as inexplicable? No, for reference to simpler and more fundamental laws is merely one method of bringing the data into a system. If the elementary law can be shown to be a part of a system, made up, for example, of other elementary laws, we have all the explanation which can be demanded. The parts are explained by being given their proper place in the whole. If the whole were in turn a part of a larger whole it could be explained in the same way. But suppose the whole were ultimate: could it be explained? Could the universe, not simply the physical universe, but the whole of reality of whatever kind, could it be explained? The only kind of explanation which could be given Iwould be a statement of the relation between this whole and its parts, and it is hard to see what other kind could be asked for. One might ask for the purpose of it all, but in the broad way in which we are conceiving 2 Jevons, Lessons in Logic, p. 268. |