There is no royal road to the cultivation of the reasoning faculties. There is but the old familiar rule: Practice, exercise, use. Nevertheless there are certain studies which tend to develop the faculties in question. The study of arithmetic, especially mental arithmetic, tends to develop correct habits of reasoning from one truth to another--from cause to effect. Better still is the study of geometry; and best of all, of course, is the study of logic and the practice of working out its problems and examples. The study of philosophy and psychology also is useful in this way. Many lawyers and teachers have drilled themselves in geometry solely for the purpose of developing their logical reasoning powers. Brooks says: "So valuable is geometry as a discipline that many lawyers and others review their geometry every year in order to keep the mind drilled to logical habits of thinking. * * * The study of logic will aid in the development of the power of deductive reasoning. It does this, first, by showing the method by which we reason. To know how we reason, to see the laws which govern the reasoning process, to analyze the syllogism and see its conformity to the laws of thought, is not only an exercise of reasoning but gives that knowledge of the process that will be both a stimulus and a guide to thought. No one can trace the principles and processes of thought without receiving thereby an impetus to thought. In the second place, the study of logic is probably even more valuable because it gives practice in deductive thinking. This, perhaps, is its principal value, since the mind reasons instinctively without knowing how it reasons. One can think without the knowledge of the science of thinking just as one can use language correctly without a knowledge of grammar; yet as the study of grammar improves one's speech, so the study of logic can but improve one's thought." In the opinion of the writer hereof, one of the best though simple methods of cultivating the faculties of reasoning is to acquaint one's self thoroughly with the more common _fallacies_ or forms of false reasoning--so thoroughly that not only is the false reasoning detected at once but also the _reason_ of its falsity is readily understood. To understand the wrong ways of reasoning is to be on guard against them. By guarding against them we tend to eliminate them from our thought processes. If we eliminate the false we have the true left in its place. Therefore we recommend the weeding of the logical garden of the common fallacies, to the end that the flowers of pure reason may flourish in their stead. Accordingly, we think it well to call your attention in the next chapter to the more common fallacies, and the reason of their falsity. CHAPTER XXVIII. Fallacious Reasoning.