Experience teaches that the distinction between the ‘I’ and the ‘not-I’ is really only a question of a habit of thought, of a form of thought, and not of an effective, certain knowledge, which carries in itself the criteria of its accuracy and certitude. When, in consequence of a morbid disturbance, our sensory nerves or their centres of perception are excited, and consciousness acquires knowledge of this excitation, it imputes to it without hesitation, according to its habit, an external cause existing in the ‘not-I.’ Hence arise illusions and hallucinations, which the patient takes for realities, and that so positively that there is absolutely no means of convincing him that he perceives facts passing within him, not outside of him. In the same manner consciousness concludes that the movements executed unconsciously are occasioned by an extraneous will. It perceives the movement, but it has not noticed that the habitual internal cause, viz., a motor image and an act of the will, has preceded it; hence it places the cause of the movement without hesitation in the ‘not-I,’ although it resides in the ‘I,’ and is only occasioned by subordinate centres, the activity of which remains concealed from consciousness. This it is which gives rise to spiritualism, which, in so far as it is in good faith and not openly a hocus-pocus, is simply a mystical attempt to explain movements, the real cause of which consciousness does not find in itself, and which it places, in consequence, in the ‘not-I.’