If he continues to gaze at the mental images which he thus sees in his vision, rapt and absorbed as he is, he may eventually mesmerize himself into a firm belief in their external reality. But whether they be Gods and saints or lights and colours, these strange visions which pass before his eyes are partly creations of the mind itself. Many so-called clairvoyant and occult phenomena are really mental projections, but it is perfectly possible for them to be so vivid as to appear as if they were outside their seer. The experiences of them have been largely, if unconsciously, created within the tortuous recesses of the narrator's own cranium. He visualizes mental images with such intensity and exuberance that the imagined forms and events appear to him as external objects. This kind of thing has now come even within the sweep of scientific investigation. A group of psychologists, professors attached to American universities, have discovered that the faculty of perceiving mental images so vividly that they appear to be outside objects is not uncommon among children, and they have bestowed the term "eidetic imagery" on this power. There is little difference between such imagining and that of those grown-up children who unconsciously create their own visions. In both cases the visions are the result of the percipient's own mental construction and have no independent existence.
-- Notebooks Category 16: The Sensitives > Chapter 15 : Illuminations > # 2
