Sleep and Its Derangements

by William A. Hammond

Cabanis[61] contends that the will is not entirely suspended during sleep; but, as will be perceived from the following quotation, he bases his argument upon the fact that movements are produced which he attributes erroneously to the action of the will, but which, like those previously referred to, are accomplished by the agency of the spinal cord. He says, speaking of the instances of persons walking while asleep:

“These rare cases are not the only ones in which during sleep movements are produced by what remains of the will; for it is by virtue of certain direct sensations that a sleeping man moves his arm to brush away the flies that may be on his face, that he draws up the bedclothes so as to cover himself carefully; or, as we have already remarked, that he turns over and endeavors to find a more comfortable position. It is the will which during sleep maintains the contraction of the sphincter of the bladder, notwithstanding the effort of the urine to escape; it is the same power which directs the action of the arm in seeking for the vase de nuit, which knows where to find it, and enables the individual to use it for several minutes and to return it to its place without being awakened. Finally, it is not without reason that some physiologists have made the will concur in the contraction of several muscles, the movements of which are necessary to the maintenance of respiration during sleep.”

All these movements, and many others of a similar character, are entirely spinal, and are altogether independent of cerebral influence. Even when we are awake, we constantly execute muscular actions through the power of the spinal cord, when the mind is intently occupied with other things. Take for instance the example of a person playing on the piano, and at the same time carrying on a conversation. Here the brain is engaged in the one act and the spinal cord in the other. So long as the player is not expert in the fingering of the instrument, he cannot divert his attention from his performance; for the whole power of the mind is required for the proper appreciation and execution of the music. But after the spinal cord has become educated to the habit, and he has attained proficiency in the necessary manipulations, the mind is no longer required to control the actions and may be directed to other subjects. The arguments of Cabanis, therefore, in favor of the partial exercise of the will during sleep, are of no force.

But the power of the will over the muscles of the body is only one of the ways in which this faculty is shown. It regulates the thoughts and the manifestations of emotion when we are awake. How utterly incapable it is of any such action during sleep we all know. A gentleman, remarkable for the ability he possesses for controlling his feelings, tells me that when he is asleep he frequently weeps or laughs at imaginary events, which, if they really had occurred to him during wakefulness, would give rise to no such disturbance. He often desires to stop these emotional manifestations, but is entirely powerless to do so. Most individuals have had similar experiences.

The theory that the will is in action during sleep is, therefore, to my mind untenable. It has probably had its origin in the idea that confounds it with desire, from which it differs so markedly that it seems strange the distinction should ever fail of being made. Locke[62] points out very clearly the differences between the two faculties. In fact they may be exerted in directly opposite ways. Desire often precedes volition; but we all, at times, will acts which are contrary to our desire, and desire to perform others which we are unable to will.

Reid[63] writes with great perspicuity on this distinction between desire and will. He says:

“Desire and will agree in this, that both must have an object of which we must have some conception; and, therefore, both must be accompanied with some degree of understanding. But they differ in several things.

“The object of desire may be anything which appetite, passion, or affection leads us to pursue; it may be any event which we think good for us, or for those to whom we are well affected. I may desire meat or drink, or ease from pain. But to say that I will meat, or will drink, or will ease from pain, is not English. There is, therefore, a distinction in common language between desire and will. And the distinction is, that what we will must be an action and our own action; what we desire may not be our own action, it may be no action at all.

“A man desires that his children may be happy, and that they may behave well. Their being happy is no action at all; their behaving well is not his action but theirs.

“With regard to our own actions, we may desire what we do not will, and will what we do not desire; nay, what we have a great aversion to.