Let us take another example. Both the supporters and opponents of woman suffrage have often decided the question without consulting at all the actual results achieved in the States where women vote. They have settled the question to their own satisfaction merely on a priori grounds. They have considered woman’s supposed mental qualities as compared with man’s, and have decided on her fitness for the ballot solely from these con­si­der­a­tions. It must be remembered, however, that before women were admitted to suffrage anywhere, deductive or a priori reasoning was the only kind possible.

It is often helpful to look at a problem from the viewpoint of different sciences. A problem in po­li­ti­cal science will very likely have an economic aspect, whether it concerns taxation, tariff, trusts or the ownership of land, and so we may look at the question solely from the viewpoint of economics. But the problem may also have an ethical aspect. If it is proposed to pass a universal prohibition law, you may ask, “Has the Government the right to interfere in this way with personal liberty?” Again, we could take a psy­cho­log­i­cal view: we would decide from our knowledge of human nature just what the effect of an alcohol prohibition law would be—whether it would not drive men to even more dangerous drugs, such as morphine and opium.

And now we come to a whole host of effective methods, all of which may be classed as comparative. The comparative method is as old as thought itself, but it is strange that even scientists did not begin to use it consciously and consistently until almost the present generation. Nowhere is it better illustrated than in modern psychology. Most of the so-called branches of psychology are merely different forms of the comparative method of treatment. “Abnormal psychology” is merely a comparison of abnormal mental types with normal mental types for the light they throw on each other. “Child study” is a comparison of the mind of the child with that of the adult. “Animal psychology” is a comparison of the actions of animals with each other and with those of man. And none of these methods is of any value except in so far as it makes use of comparison.

Often consciously used in the con­si­der­a­tion of problems is the so-called historical method. This method, as its name implies, consists in obtaining knowledge of a thing by considering its past record. The word history is popularly used in so narrow a sense, however, being restricted only to the history of nations, and often merely to the political history of nations, that we can avoid confusion by calling this method the evolutionary. In the final analysis the method is comparative, for it really consists in comparing a thing at one period of development with itself at another period.

Let us take our example from political science. The historical method, in its popular sense, has been so much used here, even to the exclusion of other methods, that it would seem needless to speak of it. But often the method has been abused and often it has not been given broad enough treatment. It traces the growth of an institution, or of an idea—personal liberty, say,—through successive periods. It notes what the path has been, and judges of the probable future tendency. But a far broader outlook than we get from this narrowly conceived “historical” method is furnished by evolutionary sociology. Here we inquire into the origin of society and of the various trades, industries, professions and pursuits of all kinds, and to do this we go far into prehistoric times.

Nowhere is the evolutionary method more strikingly seen than in biology. Since Darwin’s great theory was promulgated the science has gone forward by leaps and bounds. We have derived untold benefit from a comparison of man and animals in the light of this hypothesis; even study of the development of individual man has been aided. The discovery of the fact of evolution constituted an incalculable advance, but the method for study which it furnished was of even greater importance.

I have spoken of the comparison of man and animals “in the light of this (evolutionary) hypothesis.” This brings us to a point which must be kept in mind in practically all observation. We are often exhorted to “observe.” Presumably we are to do this “on general principles.” Such advice is about as foolish as asking us to think on general principles. Imagine for the moment what would happen if you started right now to “observe” as much as you could. You might begin with this book and notice the size of the type, the amount of margin, the quality of the paper, the dimensions of the page, the number of pages. But you have by no means exhausted the number of properties possessed by this book. You must observe that it is also combustible, that it is destructible, that it is machine made, that it is American printed, that it is such and such a price, that it weighs so many ounces, that it is flat, that it is rectangular, that its thickness is so much. . . .

The absurdity is obvious. If we started out merely to observe, with no definite purpose in mind, we could keep it up forever. And get nowhere. Nine out of every ten observations would never be put to use. We would be sinfully wasting our time. To observe most profitably, just as to think most profitably, we must have a definite purpose. This purpose must be to test the truth of a sup­po­si­tion. A concrete example will make this clear.

A man has been shipwrecked on an island and believes himself to be alone there. One day, as he is walking along the beach, he discovers footprints. How did they get there? His first assumption is that they are his own. It occurs to him, however, that he had not been near this spot for over a week, and that yesterday’s storm would have washed any footprints away. This objection is confirmed by making a footprint himself and comparing it with the one observed, and noticing that they differ markedly. The footprints being those of some one else, how did the man who made them get there? The first sup­po­si­tion is that he came in a boat. The idea of a small boat is dismissed because of the assumed great distance of this island from other land. Therefore the man must have come in a large vessel. But the footprints lead to a wet part of the sand and the tide is just going down. In this case they are very recent—made not more than a half hour ago. This being so the man who made them could not have had time to get back to any ship and sail out of sight. If he came in a ship it should be still in view. The discoverer of the footprints climbs a tree from which he can view the sea around the entire island. He can sight no vessel. The sup­po­si­tion or hypothesis that the unknown came in a ship is abandoned. Then the sug­ges­tion comes that the unknown has been on the island during the entire time that the shipwrecked man thought himself alone. This sug­ges­tion is tested in a manner similar to the others. . . .

The example sums up roughly the general process of all thought, and brings out the motive and value of observation. Let us analyze it.