One should probably never learn one thing _just because_ it will help him in learning something else, for that something else could be more economically learned by direct practice. Learning one language probably helps in learning another. A year spent in learning German will probably help in learning French. But two years spent in learning French will give more efficiency in French than will be acquired by spending one year on German and then one year on French. If the only reason for a study is that it helps in learning something else, then this study should be left out of the curriculum. If the only reason for studying Latin, for example, is that it helps in studying English, or French, or helps in grammar, or gives one a larger vocabulary in English on account of a knowledge of the Latin roots, then the study of the language cannot be justified; for all of these results could be much more economically and better attained by a direct approach. Of course, if Latin has a justification in itself, then these by-products are not to be despised. The truth seems to be that habits are very specific things. A definite stimulus goes over to a definite response. We must decide what habits we need to have established, and then by direct and economical practice establish these habits. It is true that in pursuing some studies, we acquire habits that are of much greater applicability in the affairs of life than can be obtained from other studies. When one has acquired the various adding habits, he has kinds of skill that will be of use in almost everything that is undertaken later. So also speaking habits, writing habits, spelling habits, moral habits, etc., are of universal applicability. Whenever one undertakes to do a thing that involves some habit already formed, that thing is more easily done by virtue of that habit. One could not very well learn to multiply one number by another, such as 8,675,489 by 439,857, without first learning to add. This seems to be all there is to the idea of the transfer of training. One gets an act, or an idea, or an attitude, or a point of view that is available in a new thing, thereby making the new thing easier. The methods one would acquire in the study of zoölogy would be, many of them, directly applicable in the study of botany. But, just as truly, one can acquire habits in doing one thing that will be a direct hindrance in learning another thing. Knocking a baseball unfits one for knocking a tennis ball. The study of literature and philosophy probably unfits one for the study of an experimental science because the methods are so dissimilar, in some measure antagonistic.