IX. RETROSPECT AND PROSPECT
THE SCIENTIFIC ATTITUDE OF MIND
ANY one who has not had a rigid training in science may advantageously reflect at some length upon the meaning of true scientific induction. Various illustrations in our text are meant to convey the idea that logical thinking consists simply in drawing correct conclusions as to the probable sequence of events in nature. It will soon be evident to any one who carefully considers the subject that we know very little indeed about cause and effect in a rigid acceptance of these words. We observe that certain phenomena always follow certain other phenomena, and these observations fix the idea in our mind that such phenomena bear to one another the relation of effect and cause. The conclusion is a perfectly valid one so long as we remember that in the last analysis the words "cause" and "effect" have scarcely greater force than the terms "invariable antecedent" and "invariable consequent"—that is to say, they express an observed sequence which our experience has never contradicted.
Now the whole structure of science would be hopelessly undermined had not scientific men come to have the fullest confidence in the invariability of certain of these sequences of events. Let us, for example, take the familiar and fundamental observation that any unsupported object, having what we term weight, invariably falls directly towards the centre of the earth. We express this fact in terms of a so-called law of gravitation, and every one, consciously or unconsciously, gives full deference to this law. So firmly convinced are we that the gravitation pull is a cause that works with absolute, unvarying uniformity that we should regard it as a miracle were any heavy body to disregard the law of gravitation and rise into the air when not impelled by some other force of which we have knowledge. Thanks to Newton, we know that this force of gravitation is not at all confined to the earth, but affects the whole universe, so that every two bits of matter, regardless of location, pull at each other with a force proportionate to their mass and inversely as the square of their distance.
Were this so-called law of gravitation to cease to operate, the entire plan of our universe would be sadly disarranged. The earth, for example, and the other planets would leave their elliptical orbits and hurtle away on a tangential course. We should soon be beyond the reach of the sun's beneficent influence; an arctic chill would pervade polar and tropical regions alike, and the term of man's existence would come suddenly to a close. Here, then, is a force at once the most comprehensible and most important from a human stand-point that can be conceived; yet it cannot be too often repeated, we know nothing whatever as to the nature of this force. We do not know that there may not be other starlike clusters beyond our universe where this force does not prevail. We do not know that there may not come a period when this force will cease to operate in our universe, and when, for example, it will be superseded by the universal domination of a force of mutual repulsion. For aught we know to the contrary, our universe may be a pulsing organism, or portion of an organism, all the particles of which are at one moment pulled together and the next moment hurled apart—the moments of this computation being, of course, myriads of years as we human pygmies compute time.
To us it would be a miracle if a heavy body, unsupported, should fly off into space instead of dropping towards the centre of the earth; yet the time may come when all such heavy objects will thus fly off into space, and when the observer, could there be such, must marvel at the miracle of seeing a heavy object fall towards the earth. Such thoughts as these should command the attention of every student of science who would really understand the meaning of what are termed natural laws. But, on the other hand, such suggestions must be held carefully in check by the observation that scientific imagining as to what may come to pass at some remote future time must in no wise influence our practical faith in the universality of certain natural laws in the present epoch. We may imagine a time when terrestrial gravitation no longer exerts its power, but we dare not challenge that power in the present. There could be no science did we not accept certain constantly observed phenomena as the effect of certain causes. The whole body of science is made up solely of such observations and inferences. Natural science is so called because it has to do with observed phenomena of nature.
NATURAL VERSUS SUPERNATURAL
A further word must be said as to this word "natural," and its complementary word "supernatural." I have said in an early chapter that prehistoric man came, through a use of false inductions, to the belief in supernatural powers. Let us examine this statement in some detail, for it will throw much light on our later studies. The thing to get clearly in mind is the idea that when we say "natural" phenomena we mean merely phenomena that have been observed to occur. From a truly scientific stand-point there is no preconception as to what manner of phenomenon may, or may not, occur. All manner of things do occur constantly that would seem improbable were they not matters of familiar knowledge. The simplest facts in regard to gravitation involve difficulties that were stumbling-blocks to many generations of thinkers, and which continue stumbling-blocks to the minds of each generation of present-day children.
Thus most of us can recall a time when we first learned with astonishment that the earth is "round like a ball"; that there are people walking about on the other side of the world with their feet towards ours, and that the world itself is rushing through space and spinning rapidly about as it goes. Then we learn, further, that numberless familiar phenomena would be quite different could we be transported to other globes. That, for example, a man who can spring two or three feet into the air here would be able, with the same muscular exertion, to vault almost to the house-tops if he lived on a small planet like the moon; but, on the other hand, would be held prone by his own weight if transported to a great planet like Jupiter.