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.