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, i