Years ago when I began to teach at Harvard College, we used to regard our students as roaring animals, likely to destroy whatever came in their way. We instructors were warned to keep the doors of our lecture rooms barred. As we came out, we must never fail to lock them. So always in going to a lecture, as I passed through the stone entry and approached the door my hand sought my pocket, the key came out, was inserted in the keyhole, turned, was withdrawn, fell back into my pocket, and I entered the room. This series of acts repeated day after day had become so mechanized that if on entering the room I had been asked whether on that particular day I had really unlocked the door, I could not have told. The train took care of itself and I was not concerned in it sufficiently for remembrance. Yet it remained my act. On one or two occasions, after shoving in the key in my usual unconscious fashion, I heard voices in the room and knew that it would be inappropriate to enter. Instantly I stopped and checked the remainder of the train. Habitual though the series of actions was, and ordinarily executed without conscious guidance, it as a whole was aimed at a definite end. If this were unattainable, the train stopped. All are aware how large a part is played by such mechanization of conduct. Without it, life could not go on. When a man walks to the door, he does not decide where to set his foot, what shall be the length of his step, how he shall maintain his balance on the foot that is down while the other is raised. These matters were decided when he was a child. In those infant years which seem to us intellectually so stationary, a human being is probably making as large acquisitions as at any period of his later life. He is testing alternatives and organizing experience into ordered trains. But in the rest of us a consolidation substantially similar should be going on in some section of our experience as long as we live. For this is the way we develop: not the total man at once, but this year one tract of conduct is surveyed, judged, mechanized; and next year another goes through the same maturing process. Not until such mechanization has been accomplished is the conduct truly ours. When, for example, I am winning the power of speech, I gradually cease to study exactly the word I utter, the tone in which it is enunciated, how my tongue, lips, and teeth shall be adjusted in reference to one another. While occupied with these things, I am no speaker. I become such only when, the moment I think of a word, the actions needed for its utterance set themselves in motion. With them I have only a negative concern. Indeed, as we grow maturer of speech, collocations of words stick naturally together and offer themselves to our service. When we require a certain range of words from which to draw our means of communication, there they stand ready. We have no need to rummage the dimness of the past for them. Mechanically they are prepared for our service.