e ears, few
fall into the error of seeing or hearing distinct recognizable objects
in the absence of all external impressions. In the lives of eminent men
we read of such phenomena as very occasional events. Malebranche, for
example, is said to have heard the voice of God calling him. Descartes
says that, after a long confinement, he was followed by an invisible
person, calling him to pursue his search for truth. Dr. Johnson narrates
that he once heard his absent mother calling him. Byron tells us that he
was sometimes visited by spectres. Goethe records that he once saw an
exact counterpart of himself coming towards him. Sir Walter Scott is
said to have seen a phantom of the dead Byron. It is possible that all
of us are liable to momentary hallucinations at times of exceptional
nervous exhaustion, though they are too fugitive to excite our
attention.

When not brought on by exhaustion or artificial means, the
hallucinations of the sane have their origin in a preternatural power of
imagination. It is well known that this power can be greatly improved by
attention and cultivation. Goethe used to exercise himself in watching
for ocular spectra, and could at will transform these subjective
sensations into definite forms, such as flowers; and Johannes Mueller
found he had the same power.[59] Stories are told of portrait painters
who could summon visual images of their sitters with a vividness equal
to that of reality, and serving all the purposes of their art. Mr.
Galton's interesting inquiries into the power of "visualizing" would
appear to prove that many people can at will sport on the confines of
the phantom world of hallucination. There is good reason to think that
imaginative children tend to confuse mental images and percepts.[60]

_The Hallucinations of Insanity._

The hallucinations of the insane are but a fuller manifestation of
forces that we see at work in normal life. Their characteristic is that
they simulate the form of distinctly present objects, the existence of
which is not instantly contradicted by the actual surroundings of the
moment.[61] The hallucinations have their origin partly in subjective
sensations, which are probably connected with peripheral disturbances,
partly and principally in central derangements.[62] These include
profound emotional changes, which affect the ruling mental tone, and
exert a powerful influence on the course of the mental images. The
hallucinations of insanity are due