What does the soul do in the interim?  It lives in itself, and like a pilot in a calm, like a mirror at night, a lute that no one touches, awakes new excitement.

Some psycologists, among others the count of Redern, say that the soul always acts.  The evidence is, that a man aroused from sleep always preserves a memory of his dreams.

There is something in this observation, which deserves verification.

This state of annihilation, however, is of brief duration, never exceeding more than five or six hours:  losses are gradually repaired, an obscure sense of existence manifests itself, and the sleeper passes into the empire of dreams.

Meditation XIX.

Dreams.

Dreams are material impressions on the soul, without the intervention of external objects.

These phenomena, so common in ordinary times, are yet little known.

The fault resides with the savants who did not allow us a sufficiently great number of instances.  Time will however remedy this, and the double nature of man will be better known.

In the present state of science, it must be taken for granted that there exists a fluid, subtle as it is powerful, which transmits to the brain the impressions received by the senses.  This excitement is the cause of ideas.

Absolute sleep is the deperdition or inertia of this fluid.

We must believe that the labors of digestion and assimulation do not cease during sleep, but repair losses so that there is a time when the individual having already all the necessities of action is not excited by external objects.

Thus the nervous fluid—­movable from its nature, passes to the brain, through the nervous conduits.  It insinuates itself into the same places, and follows the old road.  It produces the same, but less intense effects.

I could easily ascertain the reason of this.  When man is impressed by an external object, sensation is sudden, precise, and involuntary.  The whole organ is in motion.  When on the contrary, the same impression is received in sleep, the posterior portion of the nerves only is in motion, and the sensation is in consequence, less distinct and positive.  To make ourselves more easily understood, we will say that when the man is awake, the whole system is impressed, while in sleep, only that portion near the brain is affected.

We know, however, that in voluptuous dreams, nature is almost as much gratified as by our waking sensations; there is, however, this difference in the organs, for each sex has all the elements of gratification.

When the nervous fluid is taken to our brain, it is always collected in vats, so to say, intended for the use of one of our senses, and for that reason, a certain series of ideas, preferable to others, are aroused.  Thus we see when the optic nerve is excited, and hear when those of the ear are moved.  Let us here remark that taste and smell are rarely experienced in dreams.  We dream of flowers, but not of their perfume; we see a magnificently arranged table, but have no perception of the flavor of the dishes.