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our limited experience seems to confirm the assumption ; but our experience is very limited to bear so important and uni versal a generalization. But granted that it is so ; that fact would not be inconsistent with a real determination of the direction of physical energy by the mind. It is only neces sary to assume what seems to be an obvious fact of ex perience that psychical energy is distinct from physical energy. Recurring to what was said on a foregoing page as to the likeness of the cortex to a complicated switch board, it is obvious that the nervous energy released by the stimulation of an afferent nerve may be switched on to any one of a multitude of efferent tracks. Now, why may we not suppose this to be done by a distinct psychical entity, called the mind, without any increase or diminution of the nervous energy? Whether the motor discharge takes place wholly through one group of muscles, or is directed partly upon a definite group of muscles and partly translated into general organic tension, or is converted wholly into emo tional disturbance, it would be exactly equal to the energy transmitted to the cortex by the afferent nerve, the course it would take being determined by the choosing mind, the will. The brakeman who turns the switch which diverts a train of cars on to one of many alternate tracks neither adds to nor subtracts from the mechanical momentum of the train.
But it may be contended that the act of turning the ner vous energy into one motor path rather than another is work and involves the expenditure of energy ; and it may be asked, what, then, is this energy which controls and directs the expenditure of the physical energy, and whence comes it? Manifestly it must be either a form of mechanical energy differentiated for this function, or a wholly different and peculiar kind of energy. The former alternative is adopted by the materialist; the latter by the believer in spiritual realities. But the materialistic assumption is wholly gratuitous. Experimental Psychology has not yet been able to show an exact equation between the energy of the stimulus and that of the motor response, much less to
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