This may not be a scientific classification, but it suffices for my purpose. I have not put the most important first, but observation is the one man most relies upon. 1. Observation is God's method of filling up the inner supply of man's knowledge through the senses. He sees, feels, hears, smells, tastes, and through these avenues receives mental impressions. One can observe the lower things or the higher. Every day as I ride on the train or street cars, I observe men reading their newspapers. As a rule I can tell in a few minutes what a man's mental hunger is by watching him read. He chooses the pink sheet and devours with avidity the stories of prize fights. He turns to the pages devoted to courts and reads the accounts of murder trials or of scenes where lawyers quarrel or jangle and where witnesses testify to disgusting and loathsome things. Another man is interested in clean athletics and reads with interest of college football, Marathon games, and the like. Still another is absorbed in the news of a higher nature, a meeting of the Hague Peace Conference, the endeavors of statesmen to bring about a better understanding between the North and the South, between nations. In other words, a man takes what his appetite craves out of the newspaper. Just so it is with all life. Men take whatever their appetites crave. If the appetite is false, unnatural, abnormal, they take injurious food. Only when the depraved appetite becomes changed into natural, normal hunger, is the right kind of food sought and found. Yet there is immeasurably more of the pure, good food to satisfy the perfect, normal hunger, than there is of the carrion which the vulture instincts in us crave. 2. Reading. While I have put this under a separate head, it really belongs under the head of observation, for the reading of books is but observation of the observations of other men. Yet, as I shall show later, this is a special field which one should endeavor to glean with care. 3. Intuition. To the really normally hungry soul, this is the chief, indeed, the only source of spiritual food. It is what Emerson called the "Oversoul," and what Doctor Buck meant when, in speaking of Walt Whitman, he said he possessed the "cosmic conscience." It is receptiveness to universal truth, Divine truth, that truth which knows no time, no place, no boundaries of nationality, no difference in creed, in sect, in sex, in color, but that, like the sun, shines alike upon all, whether bond or free, rich or poor, learned or unlearned, black, white, brown, or red, savage or civilized. It is the spirit that possessed--in varying degrees--Gautama, Buddha, Confucius, Mahomet, Jesus, Joan of Arc, Emerson, Browning, Whitman, all great souls who have seen the truth universal and recorded it for the uplift and ennobling of mankind.