350 THE POPULAR SCIENCE MONTHLY. 



which some exaggerate and others deny, is simply the force of 

 ideas and feelings. We can not bring too much scientific exact- 

 ness to the determination of the extent and limitations of this 

 force. We start from the principle that every idea tends to real- 

 ize itself; and it does so in fact, if it is not counterbalanced by a 

 superior force. The principle of the struggle for existence and of 

 selection is applicable, therefore, to ideas not less than to living 

 individuals and species. A selection is produced in the brain in 

 favor of the strongest and most exclusive idea, which carries the 

 whole organism. The child's brain is a battlefield of ideas and 

 the impulses they generate ; every new idea is an additional force 

 encountering ideas already installed and impulses already devel- 

 oped. Education is, then, a work of intellectual selection. Let us 

 suppose a mind still void, into which is abruptly introduced the 

 representation of movement, the idea of some action, as of raising 

 the arm. The idea being solitary and without any counterpoise, 

 the disturbance begun in the brain takes the direction of the arm, 

 because the nerves abutting in the arm have been disturbed by 

 the representation of it; consequently the arm rises. To think 

 of a movement is to begin it. A movement once existing can not 

 be lost, but is communicated as of necessity from the brain to the 

 organs unless it is arrested by some other representation or im- 

 pulsion. This propagation of motion is assured physiologically 

 by the symmetry of the limbs, which tend to execute the same 

 movement in succession. The brain provides the theme and the 

 limbs reproduce it, and we have sympathy and synergy of the 

 organs. The contagion of the idea to the limbs is infallible if the 

 idea is solitary or predominant. We call this the law of idea- 

 forces. 



Chevreul's well-known experiments with the exploratory 

 pendulum and the divining rod show that, if we represent to our- 

 selves a motion in any direction, the hand will unconsciously 

 realize it and communicate it to the pendulum. The tipping table 

 realizes a movement we are anticipating, through the interven- 

 tion of a real movement of the hands, of which we are not con- 

 scious. Mind-reading, by those who divine by taking your hand 

 where you have hidden anything, is a reading of imperceptible 

 motions by which your thought is translated without your being 

 conscious of them. In cases of fascination and vertigo, which are 

 more visible among children than among adults, a movement is 

 begun the suspension of which is prevented by a paralysis of the 

 will, and it carries us on to suffering and death. When a child, I 

 was navigating a plank on the river without a thought that I 

 might fall. All at once the idea came like a diverging force, pro- 

 jecting itself across the rectilinear thought which had alone 

 previously directed my action. It was as if an invisible arm 



