causes, we are greatly aided, and much useles labor is saved, by such an indication. Thus, Sir H. Davy discovered the metallic basis of potash. But there are other alkalies in many of their sensible properties nearly allied to potash. How natural was it for him to expect that the same laws governed them all, and that they all were formed in the same manner from metallic bases! manner. 3. Analogy is frequently used by the orator with great effect. Thus, if it is admitted that a man has acted in one way at one time, there is no reason why he might not be expected to act in the same way at another time. Or, if it is honorable for one man to act in a particular manner in one case, there can be no reason why it is not honorable for another man, in a case essentially alike, to act in a similar This mode of reasoning is used with the happiest success by Erskine, in the introduction of his argument for Stockdale. He commences by alluding to the fact that, though connected by ties of the closest intimacy with the political party who had directed the prosecution, yet, Mr. Stockdale had not hesitated to entrust him with his defence. "This, however, is a matter of daily occurrence. lied is the character of the English bar, that no political bias ever interferes with the discharge of the duty of an advocate; that, whatever may be our public principles, or the private habits of our lives, they never cast even a shade across the path of our professional duties. If this be characteristic of the bar of an English court of justice, what sacred impartiality may not every man expect from its jurors and its bench." Many similar instances may be found in the speeches of this eminent orator, perhaps the most consummate advocate of modern times. He adds, So unsul It is, however, obvious, that this mode of reasoning is liable to great abuse. The whole force of the argument depends on the similarity of the cases. But if an advocate can present cases seeming to be similar, while, in fact, they are widely diverse, he may draw from them the most erroneous conclusions. It is, therefore, the business of an opponent, or of an inquirer after truth, to examine reasoning of this kind with the closest scrutiny; and, when it is defective, point out the dissimilarity of the cases, and show the result to which such analogies would lead, if we allowed them to form the foundation of our judgment. Probable evidence REFERENCES. Stewart, vol. ii., chap. 2, sec. 4; Locke, Book 4, chap. 15; Abercrombie, Part 2, sec. 3. Induction-Reid, chap. 6, sec. 24; Stewart, vol. ii., chap. 4, sec. 1; Cousin, chap. 9. Analogy-Reid's Inquiry, Essay 1, chap. 4; Stewart, vol. ii., chap. 2, sec. 4, chap. 4, sec. 4; Locke, Book 5, chap. 16, sec. 12; Abercrombie, Part 3, sec. 4. Herschel's Discourse on the Study of Natural Philosophy. Remarks on Analogical Reasoning in Whately's Rhetoric. SECTION V. ON THE IMPROVEMENT OF THE REASONING POWERS. It is appropriate to close this chapter with a few suggestions on the manner of improving the reasoning powers. If the remarks in the preceding pages are correct, it will appear that the process which we employ in reasoning is, in all cases, essentially the same. Our object is to show such a relation between the known and the unknown, that, if one be true, the other is equally true; or, if one be. only probble, the other is equally probable. If our premises are denied, we proceed to show their relation to something better known and more universally admitted, and thus fall back, step by step, until we rest upon those elementary truths which are given us in the constitution of the human intellect. From these, in the first place, all our knowledge proceeds. The manner in which we accomplish this is by syllogism. We show that what is true of a class is true of every individual under that class By making it evident that individuals or species are included under classes to which they were not supposed to belong, or that a predicate can be affirmed of a subject which could not have been affirmed of it before, new knowledge is evolved, and the domain of science is enlarged. To proceed in this manner is, I suppose, the instinct of our nature. A human being begins to reason almost as soon as he begins to think; and were he incapable of reasoning, that is, of inferring a conclusion from premises, we should at once perceive that he was destitute of a rational soul, or deficient in an important element of our intellectual nature. Logicians unfold the process and develop the laws by which reasoning is performed, and thus enable us the better to distinguish between valid arguments and sophisms. To be able to do this is of great utility in the work of mental cultivation. We thus are rendered capable of determining whether our reasonings are, or are not, in accordance with the laws of the human mind. When this attainment has been made, we can rely with confidence upon the decisions of our own understanding. This is an important condition of all intellectual progress. We can never proceed boldly in the work of investigation, until we can say, with Sir Isaac Newton, "When I see a thing to.be true, I know it is true.” If, then, we would cultivate our reasoning power with uccess, it is important to understand the nature of the human mind, and especially the process by which it establishes truth by reasoning. The first of these is treated of in works on intellectual philosophy. This, however, is not alone sufcient for our purpos The whole subject of reasonin in all its ramifications, is unfolded in the science of logi. By a diligent study of this science, our acuteness ill be greatly sharpened, and, what is probably of greater consequence, the mind not only becomes accustomed to all the forms of reasoning, but learns instinctively to reject every conclusion not warranted by logical principles. I lately met with the following curious illustration of the utility of the study of logic in cultivating the power of the mind: "The Asiatic Journal, 1827, records the following instance of acuteness in a young brahmin. After the introduction of juries into Ceylon, a wealthy brahmin, whose unpopular character had rendered him obnoxious to many, was accused of murdering his nephew, and put upon trial. He chose a jury of his own caste; but so strong was the evidence against him, that twelve out of thirteen of the jury were thoroughly convinced of his guilt. The dissentient juror, a young brahmin of Camisseram, stood up, declared his conviction that the prisoner was the victim of a conspiracy, and desired that all the witnesses should be recalled. He examined them with extraordinary dexterity and acuteness, and succeeded in extorting from them such proofs of their perjury, that the jury, instead of consigning the prisoner to an ignominious death, pronounced him innocent. The affair made much noise in the island, and the chief justice, Sir Alexander Johnston, sent for the juror who had so distinguished himself, and complimented him on the talents he had displayed. The brahmin attributed his skill to the study of a book which he called 'The Strengthener of the Mind.' He had obtained it from Persia, and had translated it from the Sanscrit, into which it had been rendered from the Persian. Sir Alexander Johnston expressing a curiosity to see the book, the brahmin brought a Tamil manuscript, on palm leaves, which Sir Alexander found, to his infinite surprise, to be the 'Dialectics of Aristotle.'" I regret that I am not able to verify this anecdote by a reference to the original work. I give it as I found it in a periodical on education. The study of rules and the comprehension of principles will, however, be of very little value, unless our knowledge, as we have before recommended, be reduced to practice. By the habitual practice of earnest investigation, without any knowledge of the rules of logic, a man will become an able reasoner; while, without this practice, no matter what be his understanding of the rules, he will never acquire the power of convincing others. 2. I, therefore, remark that the power of ratiocination may be improved by the study of works of a syllogistic character. Among these, it is common to assign the first place to the pure mathematics. A geometrical demonstration is composed of a succession of pure syllogisms, free from any admixture of contingent truth, and receiving as premises only what every human mind must necessarily admit. The appeal is made exclusively to the understanding; the conceptions are definite and precise, and the conclusions follow from their own intuitive evidence. This, then, would seem to present the simplest and purest exercise of the reasoning power. For this cause, the mathematics have always formed an important branch of a liberal education. They give exercise to the reasoning power, and they may be pursued at an early period of life, when other reasoning could not be so easily comprehended. On the use of the mathematics for the purpose of intellectual cultivation, however, the highest authorities on the subject of education differ. Sir W. Hamilton * contends, *On the Study of the Mathematics as an Exercise of the Mind.- Discus sions on Philosophy, etc. London, 1852: pp. 256-327. |