to the belief in a spiritual light, we are still uncertain as to whether the seeing of such a light is a physical symptom of hallucination.  This is the opinion of M. Lelut, as given in his Amulette de Pascal (p. 301):  ’This globe of fire . . . is a common constituent of hallucinations of sight, and may be regarded at once as their most elementary form, and their highest degree of intensity’.  M. Lelut knew the phenomenon among mystics whom he had observed in his practice as an ‘alienist’.  He also quotes a story told of himself by Benvenuto Cellini.  If we can admit that this hallucination of brilliant light may be produced in the conditions of a seance, whether modern, savage, or classical, we obtain a partial solution of the problem presented by the world-wide diffusion of this belief.  Of course, once accepted as an element in spiritualism, a little phosphorus supplies the modern medium with a requisite of his trade. {68a}

Returning to Iamblichus, he classifies his phantasmogenetic agencies by the kind of light they show; greater or less, more or less divided, more or less pure, steady or agitated (ii. 4).  The arrival of demons is attended by disturbances. {68b} Heroes are usually very noisy in their manifestations:  a hero is a polter-geist, ‘sounds echo around’ (ii. 8).  There are also subjective moods diversely generated by diverse apparitions; souls of the dead, for example, prompt to lust (ii. 9).  On the whole, a great deal of experience is needed by the thaumaturgist, if he is to distinguish between one kind of manifestation and another.  Even Inquisitors have differed in opinion.

Iamblichus next tackles the difficult question of imposition and personation by spirits.  Thus a soul, or a spirit, may give itself out for a god, and exhibit the appropriate phantasmagoria:  may boast and deceive (ii. 10).  This is the result of some error or blunder in the ceremony of evocation. {69} A bad or low spirit may thus enter, disguised as a demon or god, and may utter deceitful words.  But all arts, says our guide, are liable to errors, and the ‘sacred art’ must not be judged by its occasional imperfections.  We know the same kind of excuses in modern times.

Porphyry went on to ask questions about divination and clairvoyance.  We often ascertain the future, he says, in dreams, when our bodies are lying still and peaceful:  when we are in no convulsive ecstasy such as diviners use.  Many persons prophesy ’in enthusiastic and divinely seized moments, awake, in a sense, yet not in their habitual state of consciousness’.  Music of certain kinds, the water of certain holy wells, the vapours of Branchidae, produce such ecstatic effects.  Some ‘take darkness for an ally’ (dark seances), some see visions in water, others on a wall, others in sun or moon.  As an example of ancient visions in water, we may take one from the life of Isidorus, by Damascius.  Isidorus, and his biographer, were acquainted with women who beheld in pure water in a glass vessel the phantasms of future events. {70a} This form of divination is still practised, though crystal balls are more commonly used than decanters of water.  Ancient and modern superstition as in the familiar case of Dr. Dee, attributes the phantasms to spiritual agency