tangible 'sign,' and he did not shrink from investigating the
thaumaturgy of his age. His letter of inquiry is preserved in
fragments by Eusebius, and St. Augustine: Gale edited it, and, as
he says, offers us an Absyrtus (the brother of Medea, who scattered
his mutilated remains) rather than a Porphyry. {65a} Not all of
Porphyry's questions interest us for our present purpose. He asks,
among other things: How can gods, as in the evocations of gods, be
made subject to necessity, and _compelled_ to manifest themselves?
{65b}

How do you discriminate between demons, and gods, that are manifest,
or not manifest? How does a demon differ from a hero, or from a
mere soul of a dead man?

By what sign can we be sure that the manifesting agency present is
that of a god, an angel, an archon, or a soul? For to boast, and to
display phantasms, is common to all these varieties. {65c}

In these perplexities, Porphyry resembles the anxious spiritualistic
inquirer. A 'materialised spirit' alleges himself to be Washington,
or Franklin, or the lost wife, or friend, or child of him who seeks
the mediums. How is the inquirer, how was Porphyry to know that the
assertion is correct, that it is not the mere 'boasting' of some
vulgar spirit? In the same way, when messages are given through a
medium's mouth, or by raps, or movements of a table, or a
planchette, or by automatic writing, how (even discounting
imposture) is the source to be verified? How is the identity of the
spirit to be established? This question of discerning spirits, of
identifying them, of not taking an angel for a devil, or vice versa,
was most important in the Middle Ages. On this turned the fate of