to appear real. The roots
of such a phenomenon are strictly organic, and belong to the centres in
which the image is formed, as we have already observed; this image
sometimes stands out in such vivid relief on the psychical space that it
seems to be an external, not, as it usually appears in less vivid form,
an internal intuition. The hallucinations which Nicolai describes
himself to have experienced may be taken as a classical example. When
Andral was returning from an autopsy, he clearly saw the corpse
stretched before him as he entered his room. Goethe, Byron, and many
others, have been affected in the same way. I myself have occasionally
had hallucinations of the kind when in a perfectly healthy condition of
mind and body; one, in particular, of a very vivid character, occurred
when I awoke one morning and seemed to see a tall and venerable priest
entering my chamber. It is needless to multiply examples; similar facts
abound in classic books in English, French, German, and other languages.
Let us rather study the phenomenon and trace its origin.

It is clear on the one side that the images of the hallucinations of
sight or hearing appear to have a real existence, so that they may be
observed and studied with ease; and it is also certain that this image
has no external existence, and is simply a cerebral fact, due to the
organs adapted for perception. Without considering the cause of the
external projection, to which I have already alluded, since perhaps its
physiological and psychical genesis is not yet fully understood, we
must consider the image, so far as it is believed to be real.

In cases of normal hallucination the reason is intact, and the observer
is conscious of the illusion, yet notwithstanding this positive judgment
the image has an appearance of complete reality. The cause of this
illusion is evidently the same as that of the illusions of dreams, and
of the origin of myth; namely, that everywhere and always the mental or
natural phenomenon and its image are respectively entified. In the
normal waking state, habit and other causes on which we have touched
render our ideas of things altogether immaterial, as merely psychical
forms and representative signs, but when the excitement of the organs
increases, so as to present them to the consciousness as objective
images, then, owing to the interruption of the ordinary process, they
are suddenly entified, and appear as an external phenomenon.
Hallucinations