111. Those who do not admit that there is an incorporeal and invisible world,
fancy they can explain everything by the word hallucination. The definition of this
word is well known ; it means the error, the illusion, of one who believes himself to
experience perceptions which he does not experience in reality; it comes from the Latin
word, hallucinari, to err ; but the learned have not yet, so far as we know, explained the
cause of the fact expressed by this word.
As optics and physiology appear to have no secrets for their devotees, how is it
that the latter have not yet explained the nature and source of the images, which, under
certain circumstances, present themselves to our consciousness? They would fain
explain everything by the laws of matter; let them then deduce from those laws a theory
of hallucination, capable of giving a rational explanation of the facts comprised under
that term.
