If we allow ourselves to be guided by the concept of separability, we shall now find that we have exhausted the whole series of possible problems, for we have examined all the possible separations between the consciousness and its objects; but if we use another concept, that of unconsciousness, we can go further and propound a new problem: can the consciousness become unconscious? But it is proper first to make a few distinctions. It is the rôle of metaphysics to make distinctions.[31]
Unconsciousness presupposes a death of the consciousness; but this death has its degrees, and before complete extinction we may conceive it to undergo many attenuations. There is, first, the diminution of consciousness.
Consciousness is a magnitude capable of increase and decrease, like sensation itself. According to the individual, consciousness may have a very large or a very small field, and may embrace at the same time a variable number of objects. I can pay attention to several things at the same time, but when I am tired it becomes more difficult to me. I lose in extension, or, as is still said, the field of consciousness is restricted. It may also lose not only in extent of surface, but in depth. We have all of us observed in our own selves moments of obscure consciousness when we understand dimly, and moments of luminous consciousness which carry one almost to the very bottom of things. It is difficult to consider those in the wrong who admit, with Leibnitz, the existence of small states of consciousness. The lessening of the consciousness is already our means of understanding the unconscious; unconsciousness is the limit of this reduction.[32]
This singular fact has also been noticed, that, in the same individual there may co-exist several kinds of consciousness which do not enter into communication with each other and which are not acquainted with each other. There is a principal consciousness which speaks, and, in addition, accessory kinds of consciousness which do not speak, but reveal their existence by the use of other modes of expression, of which the most frequent is writing.
This doubling or fractionation of the consciousness and personality have often been described in the case of hysterical subjects. They sometimes occur quite spontaneously, but mostly they require a little suggestion and cultivation. In any case, that they are produced in one way or other proves that they are possible, and, for the theory, this possibility is essential. Facts of this kind do not lead to a theory of the unconscious, but they enable us to understand how certain phenomena, unconscious in appearance, are conscious to themselves, because they belong to states of consciousness which have been separated from each other.
A third thesis, more difficult of comprehension than the other two, supposes that the consciousness may be preserved in an unconscious form. This is difficult to admit, because unconsciousness is the negation of consciousness. It is like saying that light can be preserved when darkness is produced, or that an object still exists when, by the hypothesis, it has been radically destroyed. This idea conveys no intelligible meaning, and there is no need to dwell on it.
We have not yet exhausted all the concepts whereby we may get to unconsciousness. Here is another, the last I shall quote, without, however, claiming that it is the last which exists. We might call it the physiological concept, for it is the one which the physiologists employ for choice. It is based upon the observation of the phenomena which are produced in the nervous system during our acts of consciousness; these phenomena precede consciousness as a rule, and condition it. According to a convenient figure which has been long in use, the relations of the physiological phenomenon to the consciousness are represented as follows: the physiological phenomenon consists in an excitement which, at one time, follows a direct and short route from the door by which it enters the nervous system to the door by which it makes its exit. In this case, it works like a simple mechanical phenomenon; but sometimes it makes a longer journey, and takes a circuitous road by which it passes into the higher nerve centres, and it is at the moment when it takes this circuitous road that the phenomenon of consciousness is produced. The use of this figure does not prejudge any important question.
Going further, many contemporary authors do not content themselves with the proposition that the consciousness is conditioned by the nervous phenomenon, but suggest also that it is continually accompanied by it. Every psychical fact of perception, of emotion, or of idea should have, it is supposed, a physiological basis. It would therefore be, taken in its entirety, psycho-physiological. This is called the parallelist theory.
We cannot discuss this here, as we shall meet with it again in the third part of this book. It has the advantage of leading to a very simple definition of unconsciousness. The unconscious is that which is purely physiological. We represent to ourselves the mechanical part of the total phenomenon continuing to produce itself, in the absence of the consciousness, as if this last continued to follow and illuminate it.