truism in the public mind that a mere specialist grows more narrow every day of his life, and there seems to be plenty of evidence in one's environment to give rise to such speculation. The argument in favor of liberal culture before a man takes up his specialty is based upon a recognition of the fact that knowledge of one kind only predetermines a man to be able to appreciate and interpret things of a similar nature, and these merely. There are two reasons for this, as one can readily see from a little study of humanity around him. In the first place, what a man knows determines what he is interested in; and common-sense philosophy has often declared that people are essentially selfish, because they are interested only in their own kinds of business, their own pursuits, their own specialties, and they lack that many-sided interest which is necessary for any title to unselfishness. The lawyer feels little interest in what the medical fraternity are doing, and perhaps will never be seen at a medical lecture; the scholar, pure and simple, troubles himself little about questions of government, and is a very insignificant warrior indeed in the political camp. The mechanic reads theology or listens to a theological sermon with the greatest difficulty. But each of these types has the deepest interest for readings, lectures, and everything else that relate to his own specialty, or to the thing he is most familiar with. It sometimes happens, it is true, that a poet may be interested in psychology or theology, but this is the case only when he is already well versed upon these subjects; and other apparent exceptions to the general rule may probably be explained in the same way.
The second point in proof of this law, that what one knows determines what he can get to know, is that, psychologically speaking, ideas create the ability to appreciate and interpret other ideas of a similar nature. This also may be abundantly illustrated by the circumstances of daily life. A man very widely read in history may be unable to understand a lecture upon biology, mechanics, or any subject unrelated to history. The general power which he has accumulated in his historical researches can not be applied to the ready and easy mastery of all sorts of things, as the old psychology stoutly maintained. Again, one who has pursued mathematical studies to great length is not thereby qualified to become a statesman; the power which may be generated by the study of mathematics is not transferable immediately to the solution of social problems. Educational psychology, then, may be said to declare in a very broad way that ideas create capacity for the reception of ideas of similar kind, but that there is practically no such thing as the acquisition of general power by the mastery of special subject-matter. In explanation of this practically, it should be said that any kind of
