Читать книгу Psychology: an elementary text-book - Hermann Ebbinghaus - Страница 14

Popular thought, supported by desires common to all human beings, readily accepts the view that mind is essentially different from matter, that its laws are in every respect different from the laws of material nature, and that the brain, being a part of the material nature, is simply the special tool used by the mind in its intercourse with nature. Consider what a contrast seems to exist between logical certainty and the mere probability derived from more or less deceptive sense impressions, between voluntary attention and sensual desire, between religious inspiration and ordinary perception, artistic creation and everyday work. Nevertheless, these highest as well as the lowest activities of the mind need a tool with which they can get into communication with the world; and this tool, says popular thought, is the brain. By means of this tool the mind can take possession of the world and shape it at will. This explanation of the functional relation between the mind and the nervous system agrees well with the facts above discussed concerning brain weight and intelligence, and nervous pathology and mental abnormality. That the magnitude, the architecture, the normal condition of a tool have an influence on the task performed, is plain enough. Many a piece of music can be played on a large organ having a great variety of stops, whereas its performance on a small instrument would be impossible. Raffael might have deserved the name of a great painter if born without arms, but the world would never have known it.

The facts of localization of function, however, do not agree so well with this tool conception of the brain, which always leads us back again to the theory that the mind takes hold of its tool at a single point. If the mind can suffer or produce this change only here, that change only there, it is difficult to see why we should regard it as an altogether separate entity. Some have pointed out, as an analogy, that truth too is everywhere, and because of its absolute unity, everywhere in its totality, without being bound to space and time. I must doubt, however, if truth is present where such analogies are worked out, for nothing can be less clear than the assertion that truth has unity. Mind is not everywhere in its totality, neither in the brain nor in the whole world. It is partly here, partly there; as seeing mind it is in the occipital convolutions of the brain, as hearing mind in the temporal convolutions. Thus we are forced, if we regard the brain as the mind’s tool, to regard the mind as an entity possessing spatial form. If we reject this conclusion, we must also reject the premise that the brain is the mind’s tool.

There are two other difficulties of very considerable importance. One of them is compliance with the principle of the conservation of energy. If mind is an entity independent of the brain, if the brain is a tool which mind can use arbitrarily, without having to obey the laws of the material world, there would be a serious break in the continuity of natural law, and the principle of the conservation of energy would suffer an exception.

Until recently it was, not probable, but at least possible, that this principle of the conservation of energy was not strictly correct when applied to conscious beings, especially to man. But in recent years direct experiment has proved that it applies to the dog, and even to man. In an animal performing no gross muscular work the energy supplied by the food is completely transformed into heat, which is absorbed by the animal’s surroundings. Rubner has found as the result of very exact measurements that the heat produced by an animal during several weeks is within one half of one per cent (that is, within the probable error) equal to the quantity of chemical energy received from the food. One might think that it would be rash to apply conclusions reached by experimenting on a dog to man, whose mental life stands on a much higher level. But even this objection has been removed by Atwater. He performed similar experiments on five educated persons, varying the conditions of mental and muscular activity or relative rest. The result is the same. Taking the total result, there is absolute equality between the energy supplied and the energy given out; in the human organism, mind has thus been proved to be subject to the laws of the natural world.

The second difficulty spoken of consists in the fact that, accepting the view which regards the brain as the mind’s tool, we cannot well avoid regarding the mind as a kind of ghost or demon, similar to the demons with which the imagination of primitive peoples populates the universe—gaseous and usually invisible men, women, giants, or dwarfs. Mankind has always felt strongly inclined to believe in the existence of such demons, and is still fond of making them the subjects of fairy tales and similar stories. But the more mature experience of the last centuries of human history has eliminated them from our theories of the actual world and assigned them their proper places in tales and mythology. Winter and summer, rain and sunshine, even the organic processes in the heart or the spinal cord are understood only by excluding from the explanation the assumption of such demons. The same is by analogy true for the processes in the brain, for the brain is not likely to be an exception to the rule. It is more difficult, of course, to determine directly whether such a demon exerts his influence in the inaccessible cavity of the skull than it is on the street or even in a haunted house. But no assertion is entitled to be regarded as true merely because we cannot go to the place in question and observe that it is false. Why not assert that heaven is located on the back side of the moon and hell in the center of the sun, merely because no one can see with his own eyes that they are not there? We must make only those assumptions which, considered from all points of view, have a high degree of probability, not those which flatter our vanity or appeal to us as the fashionable belief of the time. Now, it does not seem probable that our brain is the residence of a separable demon, no matter whether we attribute to him the power of changing at will the total amount of energy contained in our body, or conceive his activity, as some psychologists do, as a new form of energy added to the mechanical, thermal, electric, chemical, and so on,—requiring only an additional transformation of energy and not breaking down the principle of its conservation.