Page:Popular Science Monthly Volume 28.djvu/117

Rh you read, arranged schematically, the psychical processes, which, for the sake of argument, we may assume are carried on by the mind in these portions of the cortex.

I wish to point out that we have structurally and physiologically demonstrated with great probability the paths and centers of these psychical actions. There is no break: the mere sight of an object causes a stream of energy to travel through our sense areas, expanding as it goes by following the widening sensory paths here represented, and at the same time we feel our intellect learns that new ideas are rising up and finally expand into the process of deliberate thought, concerning which all we know is from that treacherous support, namely, introspection.

Then come impulses to action, and these follow a converse path to the receptive one just described; the nerve-energy is concentrated more and more until it culminates in the discharge of the motor corpuscles. We might represent the whole process of the voluntary act by two fans side by side, and the illimitable space above their arcs would serve very well to signify the darkness in which we sit concerning the process of intellectual thought,

What I have hastily sketched is the outline of the process of an attentive or voluntary act. I say attentive advisedly, for I wish now to put forward the view that the proper criterion of the voluntary nature of an act is not the mere effort that is required to perform it, but is the degree to which the attention is involved. The popular view of the volitional character of an act being decided by the effort to keep the action sustained is surely incomplete, for in the first place we are not seeking to explain our consciousness of an effort; we endeavor to discover the causation of the effort. Our sense of effort only comes when the will has acted, and that same sense is no doubt largely due to the information which the struggling muscle sends to the brain, and possibly is a conscious appreciation of how much energy this motor corpuscle is giving out.

Now, to give you an example. I see this tambour, and decide to squeeze it, and do so. Now, this was a distinctly voluntary act; but the volitionary part of it was not the effort made, it was the deliberate decision to cause the movement. I may now point out that in this whole process we say, and say rightly, that our attention is involved so long as we are deliberating over the object; that as soon as another object is brought to us our attention is distracted, that is to say, turned aside.

All writers are agreed that the attention can not be divided, that we really only attend to one thing at once. It seems to me that this is so obvious as not to require experimental demonstration; but I have led up to this point because I now wish to refer to the third part of my subject, namely, the question as to whether we have a really double nervous system or not. But, by way of preface, let me