Elements of the philosophy of the human mind. By Dugald Stewart. Rev. and abridged, with critical and explanatory notes, for the use of colleges and schools. By Francis Bowen ...

192 DREAMGING.
mind appears to retain some power over it; but as, even in
these cases, the motions which are made consist rather of a
general agitation -of the whole system, than of the regular
exertion of a particular member of it, with a view to produce a
certain effect; it is reasonable to conclude, that in perfectly
sound sleep, the mind, although it retains the power of volition,
retains no influence whatever over the bodily organs.
In that particular condition of the system, which is known by
the name of incubus, [or nightmare,] we are conscious of a
total want of power over the body; and, I believe, the common
opinion is, that it is this want of power which distinguishes the
incubus fiom all the other modifications of sleep. But the
more probable supposition seems to be, that every species of
sleep is accompanied with a suspension of the faculty of voluntary motion, and that the incubus has nothing peculiar in it but
this, - that the uneasy sensations which are produced by the accidental posture of the body, and which we find it impossible
to remove by. our own efforts, render us distinctly conscious of
our incapacity to move. One thing is certain, that the instant
of our awaking, and of our recovering the command of our
bodily organs, is one and the same.
2. The same conclusion is confirmed by a different view of
the subject. It is probable, as was already observed, that when
we are anxious to procure sleep, the state into which we naturally bring the mind, approaches to its state after sleep commences. Now it is manifest, that the means which nature
directs us to employ on such occasions, is, not to suspend the
power of volition, but to suspend the exertion of those powers
whose exercise depends on volition. If it were necessary that
volition should be suspended before we fall asleep, it would be
impossible for us, by our own efforts to hasten the moment of
rest. The very supposition of such efforts is absurd; for it
implies a continued will to suspend the acts of the will.
Sleep affects the mind as it does the body. - According to the
foregoing doctrine with respect to the state of the mind in sleep,
the effect which is produced on our mental operations, is
strikingly analogous to that which is produced on our bodily