His superior medianity includes all exosomatic automatisms (Nos. 4 and 7); his inferior medianity, the classes 3 and 6. These general indications given, it is easy to see that I divide fraud into three categories, which are, moreover, susceptible of co-existing and of forming mixed types: this is the ordinary case. We have, first of all, the guilty, voluntary and conscious fraud; then the impulsive, but conscious, frequent fraud; then the unconscious and involuntary fraud, veritable normal automatism: the author cannot be held responsible for this last order of fraud, which is, moreover, very frequent with many excellent mediums. If we study the psychological mechanism of fraud, we will find variable and diverse causes. 1. CONSCIOUS AND VOLUNTARY FRAUD The most usual cause is self-interest. This is the case with charlatans, who speculate upon the credulity of the public. We must not think this is the only motive; each impostor obeys motives which are peculiar to himself. The medical student, who gave me such curious examples of fraud, was not actuated by motives of self-interest. I think it was simply for the pleasure of cheating, of taking me in, for I had often spoken to him about my suspicions. He often cheated simply as a prank; this is what happened in a seance given by a spiritistic group to convince some new converts, when my student, it appears, gave them manifestations somewhat out of the common! However, conscious and voluntary fraud raise no real psychological problem. 2. CONSCIOUS AND INVOLUNTARY OR MIXED FRAUD On the contrary, the problem originates in this order of fraud. It often happens in circles, though composed of honourable persons, that some of the sitters, who would be incapable of voluntarily committing a fraud, do not dare to accuse themselves of an involuntary movement made by them, and of which they are conscious. This can only be applied to fairly rapid movements, such as those which imitate raps or parakinetic movements. In serious seances, the sitters should give themselves the habit of openly acknowledging every involuntary movement; it will be noticed that certain persons are very prone to these movements. They often end by being ashamed of accusing themselves so often, and thus fraud from timidity: I have met with this, especially among women. It is one of the reasons which make me condemn all experiments for the production of movements with contact. Timidity is the usual cause of this kind of fraud: the psychological problem raised is simple. 3. UNCONSCIOUS AND INVOLUNTARY FRAUD