ness and its relative
organs, which imply a constant hallucination. The most famous and acute
physicians of the insane estimate that eighty out of a hundred insane
persons are subject to hallucinations. The morbid condition which
generates them is also produced by debility, by anaemia, and the senile
decay of the cerebral organs, since they occur in dementia, idiocy, and
old age, and the physiological and mental causes are the same; the power
of fixing the attention and governing the thoughts is diminished, owing
to the weakening of the vivid consciousness of the external world,
produced by a torpidity of the afferent organs. In these cases the
recollections which are not altogether lost sometimes reappear as
hallucinations. The hallucinations of madness, in its various forms of
dementia, idiocy, and dotage, are all, apart from their morbid and
organic conditions, derived from the same source which produces myths,
dreams, and normal hallucinations; the objective entification of images
is due to the innate faculty of the perception, which leads to the
immediate personification of any given phenomenon. We have shown that,
given a sensation, there naturally arises the implicit notion of a
subject and a cause, and this natural impulse is further developed by
the influence of heredity; both in man and animals the constant and
powerful sense of individual life is infused into the phenomenon
perceived.

The various forms of madness throw a clearer light on this necessary and
primitive fact of human and animal perception. The act of sensation may
then be said to be under its own direction, and generates itself in the
automatic exercise of the brain, as in dreams, without the explicit,
disturbing, and modifying influence of reflection, and the habit of
rational analysis. The act of sensation is spontaneously completed and
developed in and with its own constituents, and since it is isolated
from other modes and exercises of thought, its real nature appears. The
hallucinations of madness, produced by the mental realization of images,
either detached or in association, prove that all our mental images or
ideas have a tendency in themselves to become real objects of
consciousness; with this difference, that a sane man recognizes these
mental entifications by their mobility and incessant alterations, which
contrast with the fixity and permanence of external and cosmic
phenomena.

The following considerations will confirm the truth