tion itself, temporarily
vacate their throne in favour of imagination. And this same suspension
of the higher intellectual functions, the stupefaction of judgment and
reflection made more complete and permanent, is just what characterizes
insanity.

We may, perhaps, express this point of connection between the illusions
of normal life and insanity by help of a physiological hypothesis. If
the nervous system has been slowly built up, during the course of human
history, into its present complex form, it follows that those nervous
structures and connections which have to do with the higher intellectual
processes, or which represent the larger and more general relations of
our experience, have been most recently evolved. Consequently, they
would be the least deeply organized, and so the least stable; that is
to say, the most liable to be thrown _hors de combat_. This is what
happens temporarily in the case of the sane, when the mind is held fast
by an illusion. And, in states of insanity, we see the process of
nervous dissolution beginning with these same nervous structures, and so
taking the reverse order of the process of evolution.[67] And thus, we
may say that throughout the mental life of the most sane of us, these
higher and more delicately balanced structures are constantly in danger
of being reduced to that state of inefficiency, which in its full
manifestation is mental disease.

Does this way of putting the subject seem alarming? Is it an appalling
thought that our normal mental life is thus intimately related to
insanity, and graduates away into it by such fine transitions? A
moment's reflection will show that the case is not so bad as it seems.
It is well to remind ourselves that the brain is a delicately adjusted
organ, which very easily gets disturbed, and that the best of us are
liable to become the victims of absurd illusion if we habitually allow
our imaginations to be overheated, whether by furious passion or by
excessive indulgence in the pleasures of day-dreaming, or in the
intoxicating mysteries of spiritualist _seances_. But if we take care to
keep our heads cool and avoid unhealthy degrees of mental excitement, we
need not be very anxious on the ground of our liability to this kind of
error. As I have tried to show, our most frequent illusions are
necessarily connected with something exceptional, either in the
organism or in the environment. That is to say, it is of the nature of
illusion in healthy