Then there is the desire for knowledge. This desire promotes a tendency to study. A man might study and study all through his life, but even if he read all the books in all the great libraries there would still remain the question, "why?" That "why" will not be answered by the books he studies, by exploring the facts which belong to outer life. In the first place nature is so profound that man's limited life is not long enough to probe its depths. Comparatively or relatively one may say that one person is more learned than another, but no one reaches true satisfaction by the outer study of life.