When we are unprepared for a question we nearly always have to have it repeated to us. Sitting in a railroad train, if the person behind us, whom we did not expect to talk to us, asks a question, it is very probable that on the first asking we shall not notice it at all, considering that it is addressed to someone else. On its repetition, it may appeal to us as addressed to ourselves, but even then we readily lose its significance because our attention has not been called to the wording of it soon enough to enable us to comprehend it thoroughly. These experiences, so familiar that we have probably all had them at some time or other, indicate how universal is the power of the mind to concentrate itself upon itself to the extent of neglecting sensations from the outer world, even though they may pass the periphery of the organism and manifestly affect the first neuron of the chain that leads up to our brain and consequently to consciousness. They do not reach the center with sufficient intensity to be understood, and a conscious act of attention must be made before we comprehend their meaning. {130} PREOCCUPATION OF MIND This is true, not only for ordinary sensations, but even for such as would ordinarily be presumed to be so insistent in their call that they could not be neglected. The concentration of mind necessary for this is not common to all mankind; it is possessed only by a few individuals whose intellect represents the larger portion of their personality. Certain of the great investigating scientific geniuses have had the faculty of so concentrating their attention upon the questions with which their intellects were engaged, that even the call of appetite did not make itself felt. Newton was one of these. Over and over again, he was known to neglect to take his meals, even though they were brought to him, and, occasionally, he would entirely forget whether he had taken a meal or not. But Newton is not an extreme exception. Most of the great mathematicians have had experiences of this kind and, indeed, mathematics seems to be that special branch of intellectual work which most readily brings about a preoccupation of mind sufficient to completely shut out the outer world for the time being. Archimedes, the great ancient mathematician, lost his life because of preoccupation with mathematical problems that kept him from telling the Roman soldiers, who had strict orders to spare him, who he was.