ative idea of the thing
naturally tend to become, or to appear to be, actual realities, even in
a strictly normal condition of mind and body. Nor do they only
implicitly tend to become such by the innate impulse of the mind, but
they actually become so in fugitive moments of which man is scarcely
conscious, and they appear to him exactly as they do in dreams. Hence it
follows that there is no hard and fast line between the sleeping and
waking states, so far as the nature of images, their source, action, and
combinations are concerned, when men are distracted in mind, and the
course of their thoughts is not voluntarily directed to some definite
object; so that by a psychological process the phenomena of the waking
state may be partly transformed into those of dreams. The vivid
character of the image, presented to the senses as if actually there, is
common to both phenomena. The way in which we begin to dream shows how,
owing to our physiological conditions, we pass through regular stages
from the waking state into that of sleep.

"Nuovo pensiero dentro a me si mise,
Dal qual piu altri nacquero e diversi;
E tanto di uno in altro vaneggiai
Che gli occhi per vaghezza ricopersi,
E il pensamento in sogno trasmutai."[33]

So Dante writes in the "Purgatorio" with deep and subtle truth. Each man
can verify for himself the exactness of the great poet's description.

I myself can readily study the phenomena of dreams, since I never sleep
without dreaming so vividly that I remember all the circumstances in the
morning. I have used all sorts of artifices in order to trace the
beginning of sleep and dreams, and always with the same result, so that
I am certain of the accuracy of experiments which have been repeated a
hundred times. I have examined other persons who have made the same
observations, all of whom agree with me.

When repose, the herald of sleep and dreams, begins, my thoughts wander
in an irregular and somewhat confused manner. As they are gradually
subjected to the associations to which they successively give rise, they
are transformed into more vivid images, a vividness which is always in
inverse proportion to the attention. This gradually produces the state
which has been described by Maury and others as hypnagogic
hallucination; that is, the images seem to be real, although the subject
is still partly awake, and the voluntary exercise of thought is lost
from time to time in this species of in