s of profoundest
unconsciousness partially awake--the question so warmly discussed by the
Cartesians, Leibnitz, etc.--need not detain us here.

Of more interest to us are the psychological and the physiological
discussions. The former seeks to settle the question by help of
introspection and memory. On the one side, it is urged against the
theory of unbroken mental activity, that we remember so little of the
lowered consciousness of sleep.[73] To this it is replied that our
forgetfulness of the contents of dream-consciousness, even if this were
unbroken, would be fully accounted for by the great dissimilarity
between dreaming and waking mental life. It is urged, moreover, on this
side that a sudden rousing of a man from sleep always discovers him in
the act of dreaming, and that this goes to prove the uniform connection
of dreaming and sleeping. This argument, again, may be met by the
assertion that our sense of the duration of our dreams is found to be
grossly erroneous; that, owing to the rapid succession of the images,
the _realization_ of which would involve a long duration, we enormously
exaggerate the length of dreams in retrospection.[74] From this it is
argued that the dream which is recalled on our being suddenly awakened
may have had its whole course during the transition state of waking.

Again, the fact that a man may resolve, on going to sleep, to wake at a
certain hour, has often been cited in proof of the persistence of a
degree of mental activity even in perfectly sound sleep. The force of
this consideration, however, has been explained away by saying that the
anticipation of rising at an unusual hour necessarily produces a slight
amount of mental disquietude, which is quite sufficient to prevent sound
sleep, and therefore to expose the sleeper to the rousing action of
faint external stimuli.

While the purely psychological method is thus wholly inadequate to solve
the question, physiological reasoning appears also to be not perfectly
conclusive. Many physiologists, not unnaturally desirous of upsetting
what they regard as a gratuitous metaphysical hypothesis, have
pronounced in favour of an absolutely dreamless or unconscious sleep.
From the physiological point of view, there is no mystery in a totally
suspended mental activity. On the other hand, there is much to be said
on the opposite side, and perhaps it may be contended that the purely
physiological evidence rather points to the conclusion that c