Certain special influences combine with these fundamental differences of attitude to favor the spread of belief in the occult; and of these the character of the beliefs as of the believers furnishes some evidence. At various stages of the discussion I have referred to the deceptive nature of the argument by analogy; to the dominating sympathy with a conclusion, and the resulting assimilation and overestimation of apparent evidence in its favor; to the frequent failure to understand that the formation of valid opinion and the interpretation of evidence in any field of inquiry require somewhat of expert training and special aptitude, obviously so in technical matters, but only moderately less so in matters misleadingly regarded as general; to bias and superstition, to the weakness that bends easily to the influences of contagion, to unfortunate educational limitations and perversions, and, not the least, to a defective grounding in the nature of scientific fact and proof. The mystery attaching to the behavior of the magnet led Mesmer to call his curative influence "animal magnetism,"--a conception that still prevails among latter-day occultists. The principle of sympathetic vibration, in obedience to which a tuning-fork takes up the vibrations of another in unison with it, is violently transferred to imaginary brain vibrations and to still more imaginary telepathic currents. The X-ray and wireless telegraphy are certain to be utilized in corroboration of unproven modes of mental action, and will be regarded as furnishing the key to clairvoyance and rapport; just as well-known electrical phenomena have given rise to the notions of positive and negative temperaments and mediumistic polar attraction and repulsion. All this results from the unwarranted and absurd application of analogies; for analogies, even when appropriate, are little more than suggestive or corroborative of relations or conceptions which owe their main support to other and more sturdy evidence. Analogy under careful supervision may make a useful apprentice, but endless havoc results when the servant plays the part of the master.