A like result, but not so aggravated, is produced, when a man limits his range of thought and action to those of his own special calling or profession; when the merchant mingles only with merchants and knows only merchandise; when the teacher knows nothing but teaching and books; when the medical man spends every waking hour and every active exercise of thought upon his healing art; when any man forgets that, in the very fact of his being a man at all, he is something greater and nobler than he can possibly be in being merely a merchant, or teacher, or doctor, or lawyer, or the possessor of any other one special art or faculty. It is true, indeed, that in order to attain to eminence in any one department, a man must bend his main energies to that one thing; and he must give to it much solitary thought and study. But no department of action is isolated. No interest is unconnected with other interests. No truth stands alone, but forms a part in the great system of truth. Study or action, therefore, which is entirely isolated, must needs be dwarfed and distorted. A man must go occasionally out of his own sphere in order fully to understand those very things with which he is most familiar. A man must study other languages, if he would hope fully to understand his own. A man must study more than languages merely if he would become a perfect linguist. The only way to understand arithmetic thoroughly is to study algebra. A parent who has only one child, and who gives his entire and exclusive attention to the study of that child, in order that he may, by a thorough understanding of its nature and disposition, be better able to teach and train it, will not be so likely to attain his object as he would if he were to spend a portion of his time in mingling with other children and in becoming acquainted with childhood generally. A teacher who should shut himself up in his own school-room, giving to it every moment of his waking hours, would not be likely to benefit so largely his own pupils, as if he were to spend a portion of his time in communing with other teachers and observing other methods besides his own. A teacher even who should mingle freely with those of his own profession, and get all the benefit to be derived from observation of the views and methods of other teachers, but should stop there, would not yet obtain that broad, comprehensive view, even of his own calling, and of the duties of his own particular school-room that he might have if he would travel occasionally beyond the walk of books and pedagogy, and become acquainted with the views and methods of men in other spheres of life, with merchants, lawyers, and doctors, with farmers, mechanics, and artisans.