In our dreams we are taken back into an earlier world. It is a world much more like that of the savage, the child, the criminal, the madman, than is the world of our respectable civilized waking life. That is, in large part, it must be confessed, the charm of dreams. It is also the reason of their scientific value. Through our dreams we may realize our relation to stages of evolution we have long left behind, and by the self-vivisection of our sleeping life we may learn to know something regarding the mind of primitive man and the source of some of his beliefs, thus throwing light on the facts we obtain by ethnographic research. This aspect of dreams has not always been kept steadily in sight, though it can no longer be said that the study of dreams is neglected. From one point of view or another--not only by the religious sect which, it appears, constitutes a "Dream Church" in Denmark, but by such carefully inquisitive investigators as those who have been trained under the inspiring influence of Prof. Stanley Hall--dreaming is seriously studied. I need not, therefore, apologize for the fact that I have during many years taken note from time to time and recorded the details and circumstances of vivid dreams when I could study their mechanism immediately on awakening, and that I have occupied myself, not with the singularities and marvels of dreaming--of which, indeed, I know little or nothing--but with their simplest and most general laws and tendencies. A few of these laws and tendencies I wish to set forth and illustrate. The interest of such a task is twofold. It not only reveals to us an archaic world of vast emotions and imperfect thoughts, but by helping us to attain a clear knowledge of the ordinary dream processes, it enables us in advance to deal with many of the extraordinary phenomena of dreaming, sometimes presented to us by wonder-loving people as awesomely mysterious, if not indeed supernatural. The careful analysis of mere ordinary dreams frequently gives us the key to these abnormal dreams.