so that upon discovering by analysis or otherwise that A is B or that A contains B, he may recall the fact that B is a sign of the existence of C. The foregoing description shows that while native ability plays an important role in the work of the great reasoner, by itself it is quite useless. Knowledge of the particular situation before one, obtained through analysis, knowledge of everything else that may throw light on the results of this analysis, however obtained, these are equally indispensable factors in the achievement of great results. In fact if one has to choose, the latter is more necessary than the former. However brilliant, therefore, the talents of the man who seeks to use his reasoning powers, whether in the world of business, politics, invention, or science, there is no success attainable without industry, energy, and the power to do drudgery, which are indispensable for the amassing of any large fund of information. Men like Edison in invention, Harriman in business, and Darwin in science, have always been tremendous workers. It follows also from our account that a man may exhibit great ability in one direction, as in business, and be a mere child in another, for instance the field of political problems. Where a study has also been made of political problems, there the fine mental equipment of the great business man is likely to show itself; but the only way to get a grasp upon political problems, or any other, is to make them a subject of special study. References. For the student who wishes to carry the study of deduction and induction a step farther than is here done, the following may be recommended. For deduction, James, Principles of Psychology, Vol. II, pp. 325-343; Briefer Course, Ch. XXII; or Creighton, An Introduction to Logic (3rd Ed.), Secs. 9, 10, and 29. For induction: Creighton, op. cit., Chs. XIII and XIV. CHAPTER II--THE PHYSICAL BASIS OF INTELLECTUAL SUCCESS AND PHYSICAL VIGOR Program of the Discussion. There are many lines of evidence for the assertion that the best working of our intellectual powers depends upon the health and vigor of the brain. Of these, however, it will be sufficient to present only one, namely, the influence upon the mental life of certain physical (material) agents, as disease (including physical injury, due to accidents and similar causes), fatigue, whether from muscular or mental exertion, and drugs. To bring the discussion within reasonable limits we shall confine ourselves to the study of the effects of these agents upon attention and memory. What is true of them holds of all the other powers of thinking. Indeed this could not be otherwise, for attention and memory enter as factors into every act of thought. The Effects of Disease. Our first topic will be the effects of disease, and we begin with the effects of disease on memory. Disease may affect memory in two different ways, either by diminishing ("depressing") it, or stimulating ("exalting") it. As we learned in an earlier chapter, what we call "memory" is really a great number of sets or systems of memories. The depression or exaltation which disease may produce may accordingly affect one, a small number, a large number, or even (especially is this true of depression) all of them. An example of depression, amounting in part to temporary destruction, of certain systems of language memories, was given in the chapter on memory. An example involving the same principle is the following. A certain surgeon who had been thrown from his horse and was injured in the head, gave the minutest directions upon coming to himself as to his treatment. But he no longer remembered that he had a wife and children, and this forgetfulness lasted three days. His professional knowledge remained unaffected; his knowledge of his relationships with human beings was for the time suspended. When any one of the memories involved in understanding, or expressing oneself in language is lost through disease, we have what is called aphasia. This is due to the injury of some special portion or portions of the brain. The injury may be caused by an accident, by a tumor, or by the stopping up of an artery carrying blood to that portion of the brain. In auditory aphasia the patient hears the words with which others address him, as well as does the normal person. But the sounds do not call up ideas of the things for which the sounds stand. The association between sound and meaning which was formed when, as a child, he learned the language, has been destroyed, or else so far weakened that one does not call up the other. In motor vocal aphasia the organs of speech are intact, and all the various sounds of which the language is composed can be uttered. But the patient can not articulate the words he wants to speak, the result of the attempt to do so being a mere jumble of meaningless sounds. In this case, the memory for the complicated movements which produce the desired sound, a memory which he acquired in learning to speak, has been lost. The ability to write or to understand written or printed language may be lost in the same manner. Any one of these diseases may occur without any of the others. However these memories are so intimately connected that in most cases the disorder of one is accompanied by disorders, greater or less, of some or all of the others. Where there is a gradual, progressive weakening, as happens frequently in old age, the memories for words tend to disappear in a fixed order, proper names going first, then the common nouns, adjectives, and verbs |