From IN SEARCH OF THE MIRACULOUS (page 109):
“At the same time as we watch the work of the centers we shall observe, side by side with their right working, their wrong working, that is, the working of one center for another; the attempts of the thinking center to feel or to pretend that it feels, the attempts of the emotional center to think, the attempts of the moving center to think and feel. As has been said already, one center working for another is useful in certain cases, for it preserves the continuity of mental activity. But in becoming habitual it becomes at the same time harmful, since it begins to interfere with right working by enabling each center to shirk its own direct duties and to do, not what it ought to be doing, but what it likes best at the moment.
In a normal healthy man each center does its own work, that is, the work for which it was specially destined and which it can best perform. There are situations in life which the thinking center alone can deal with and can find a way out of. If at this moment the emotional center begins to work instead, it will make a muddle of everything and the result of its interference will be most unsatisfactory.
In an ‘unbalanced kind of man the substitution of one center for another goes on almost continually and this is precisely what ‘being unbalanced’ or ‘neurotic’ means. Each center strives, as it were, to pass its work on to another, and, at the same time, it strives to do the work of another center for which it is not fitted. The emotional center working for the thinking center brings unnecessary nervousness, feverishness, and hurry into situations where, on the contrary, calm judgment and deliberation are essential. The thinking center working for the emotional center brings deliberation into situations which require quick decisions and makes a man incapable of distinguishing the peculiarities and the fine points of the position. Thought is too slow. It works out a certain plan of action and continues to follow it even though the circumstances have changed and quite a different course of action is necessary. Besides, in some cases the interference of the thinking center gives rise to entirely wrong reactions, because the thinking center is simply incapable of understanding the shades and distinctions of many events. Events that are quite different for the moving center and for the emotional center appear to be alike to it. Its decisions are much too general and do not correspond to the decisions which the emotional center would have made. This becomes perfectly clear if we imagine the interference of thought, that is, of the theoretical mind, in the domain of feeling, or of sensation, or of movement; in all three cases the interference of the mind leads to wholly undesirable results. The mind cannot understand shades of feeling. We shall see this clearly if we imagine one man reasoning about the emotions of another. He is not feeling anything himself so the feelings of another do not exist for him. A full man does not understand a hungry one. But for the other they have a very definite existence. And the decisions of the first, that is of the mind, can never satisfy him. In exactly the same way the mind cannot appreciate sensations. For it they are dead. Nor is it capable of controlling movement. Instances of this kind are the easiest to find. Whatever work a man may be doing, it is enough for him to try to do each action deliberately, with his mind, following every movement, and he will see that the quality of his work will change immediately. If he is typing, his fingers, controlled by his moving center, find the necessary letters themselves, but if he tries to ask himself before every letter: ‘Where is “k”?’ ‘Where is the comma?’ ‘How is this word spelled?’ he at once begins to make mistakes or to write very slowly. If one drives a car with the help of one’s mind, one can go only in the lowest gear. The mind cannot keep pace with all the movements necessary for developing a greater speed. To drive at full speed, especially in the streets of a large town, while steering with the help of one’s mind is absolutely impossible for an ordinary man.
From Maurice Nicoll Vol I of COMMENTARIES