APPLICATIONS OF PRINCIPLES. 207 Exposition by Proof is a part of Persuasion, and is named Argument. 72. VII. Inferences, Deductions, Corollaries, Applications, Consequences, may be drawn from principles, and may serve still further to elucidate them. To turn a principle to immediate account by deductive applications, necessarily engages our interest in it, besides having the same efficacy as the proofs in expanding it to the mind, and in determining its precise import. The corollaries of a geometrical proposition contribute to clear up and impress the proposition; and the like holds all through science, and through the less scientific generalities. Thus the First Law of Motion is practically applied to the beating out of dust, and to the drying of a mop; and these are good as examples in expounding the principle. The doctrine of the Expansion of Bodies by heat has a wide range of applications, both to the unravelling of difficult phenomena, as the winds, and to processes in the arts. The constitution of the Council and the Agora in early Greece is expounded by Grote with reference to its consequences, in the following paragraph: "There is yet another point of view in which it behoves us to take notice of the Council and the Agora as integral portions of the legendary government of the Grecian communities. We are thus enabled to trace the employment of public speaking as the standing engine of government and the proximate cause of obedience, to the social infancy of the nation. The power of speech in the direction of public affairs becomes more and more obvious, developed, and irresistible, as we advance towards the culminating period of Grecian history-the century preceding the battle of Charoneia. That its development was greatest among the most enlightened sections of the Grecian name, and smallest among the more obtuse and stationary, is matter of notorious fact; and it is not less true, that the prevalence of this habit was one of the chief causes of the intellectual eminence of the nation generally. At a time when all the countries around were plunged comparatively in mental torpor, there was no motive sufficiently present and powerful to multiply so wonderfully the productive minds of Greece, except such as arose from the rewards of public speaking. The susceptibility of the multitude to this sort of guidance, their habit of requiring and enjoying the stimulus which it supplied, and the open discussion, combining regular forms with free opposition, of practical matters, political as well as judicial, are the creative causes which formed such conspicuous adepts in the art of persuasion. Nor was it only professed orators who were thus produced. Didactic aptitude was formed in the background, and the speculative tendencies were supplied with interesting phenomena for observation and combination, at a time when the truths of physical science were almost inaccessible. If the primary effect was to quicken the powers of expression, the secondary, but not less certain result, was to develop the habits of scientific thought. Not only the oratory of Demosthenes and Perikles, and the colloquial magic of Socrates, but also the philosophical speculations of Plato, and the systematic politics, rhetoric, and logic of Aristotle, are traceable to the same general tendencies in the minds of the Grecian people; and we find the germ of these expansive forces in the senate and agora of their legendary government." Remark in the concluding sentence the employment of the Interesting Example. See also Extract XIII. 73. The Expository Paragraph has certain pecu、 liarities, growing out of the nature of science. In the ordinary form of composition, there are no means of indicating successive degrees of subordination; and we have to consider the best modes of overcoming the defect. In a sentence, there may be apparent a principal and sub ordinate clauses; but, in a paragraph, all the sentences are, to the eye, of equal or co-ordinate value. In a technical scientific work, subordination is indicated, (1) by indenting the letter-press, (2) by the forms of the numerical characters employed,—I., II., 1, 2, (1), (2), a, b, &c., and (3) by difference of type. When such devices are not resorted to, we have to trust, in a great measure, to the sense of the passage for deciding what is co-ordinate and what subordinate. Further assistance may be obtained, by attention to the following points :- (1.) The theme of the paragraph, to which all the rest is ministerial, should be found at the beginning, at the end, or in both. (2.) Iteration gives prominence, and therefore superiority. THE EXPOSITORY PARAGRAPH. 209 The circumstance that a thing is stated many times over, leads us to infer that it is more important and probably more comprehensive than the things stated only once. (3.) When facts are plainly made known as examples or illustrations of a theme, they are thereby declared to be in subordination to that theme. (4.) Statements of the second degree of subordination should, if possible, be included in the same sentence as their immediate principal; it being inexpedient to constitute distinct sentences of three different grades in the paragraph. (5.) After descending to a second, or to a still lower, degree of subordination, we should avoid returning to the higher grade in the same paragraph. (6.) A separate paragraph may be devoted to a series of examples or statements of a low, but uniform, degree of subordination. This is much better than mixing up the different degrees without change of paragraph. (7.) It is possible to intimate by our phraseology when we pass from one degree of generality to another:-"The following facts come under this principle; " "We give examples, or cases, of the rule; "The subordinate laws are these," &c. A subordinate statement may happen to be difficult of understanding, but we are not at liberty to expand it by iteration or otherwise, so as to raise it out of its rank. To study clearness in the expression, or to append some brief example or illustration, is all that the case allows. Mr. Herbert Spencer has introduced a division intermediate between the Sentence and the Paragraph, marked by a blank of about half an inch between two sentences. The arts of relief are essential to Exposition throughout. Monotony can neither keep up attention nor impress the memory. Even when the subject is made up naturally of monotonous or co-ordinate particulars, means must be used to raise some of them into relief. Thus in the details of Anatomy-the muscles, blood-vessels, &c.-certain leading tunctions are indicated, as, in reference to the muscles, the two great facts of the erecting and the bending of the body. 74. The leading form of the Expository Paragraph (and of Exposition generally) is the statement of a principle, followed by such a choice of iterations, obverse statements, examples, illustrations, proofs, and applications, as the case may require. Other forms of Paragraph are the Inductive (§ 61) and the Argumentative. The simplest form of Argument is the adducing of a general principle in support of a particular allegation. The fact is affirmed that the freezing of water in a close tube will make it burst; the principle adduced in proof is that water in freezing expands with great force. There is in this nothing different from the ordinary type of Exposition, except an inversion,—the fact being stated first, and the principle afterwards. An Argument may contain a succession of steps, called a chain of reasoning, and is then more difficult to follow. The precautions to be observed in this case are to reduce the number of steps to the fewest possible, and to give an adequate expression to each, yet so as to allow the whole to be grasped together. It is in such complicated reasonings that the rules of the Sentence and the Paragraph justify their importance. Paley says: "Property improves the conveniency of living. It enables mankind to divide themselves into distinct professions, which is impossible, unless a man can exchange the productions of his own art for what he wants from others; and exchange implies property. Much of the advantage of civilized over savage life depends upon this. When a man is from necessity his own tailor, tent-maker, carpenter, cook, huntsman, and fisherman, it is not probable that he will be expert at any of his callings. Hence the rude habitations, furniture, clothing, and implements of savages, and the tedious length of time which all their operations require." The chain of reasoning here is perplexed. The steps are these:-1st, Individual property enables one man to exchange valuables with other men. 2nd, Exchange allows division of or makes men more expert in their increases the produce of labor. The labor. 3rd, Division of several avocations, and so reasoning would be apparent either in this order, or in the in NEW TERMS, AN EVIL. 211 superiority of verted order :- -"The productiveness of labor is very much 75. One cause of the difficulty of understanding science is the novelty of many of the terms employed. Apart from the abstruseness of the notions, the mind is oppressed by the introduction of unfamiliar terms, sometimes in. great numbers and in close succession. This should, as far as possible, be considered in the exposition; a certain time being allowed for one strange word to become familiar before bringing forward others. It is scarcely necessary to remark that new language is in itself an evil. 76. In scientific exposition, it is imperative to observe the general maxim of proceeding from the known to the unknown. In describing an object of Natural History, or in expounding a great principle, reference should be made, in the first instance, to the existing knowledge of those addressed; all which should be rendered available in bodying forth the new matter. No one has more assiduously endeavored to avoid unnecessary technicalities of language, and to turn to account the previous knowledge of the general reader, than Dr. Arnott in his Elements of Physics. Coll. B. and |