CHAPTER IV.

OF DIVISION.

§ 87. DIVISION is that process of explanation which exhibits the theme through its specific or similar parts.

This process often gives the leading departments of a discourse; and the more subordinate development of the theme under the principal departments in all discourse is effected to a great extent through this process. In truth this process and the next to be exhibited partition stand in about the same relation to the construction of discourse in which multiplication and division stand to arithmetical computation generally. Of not less service in securing facility and accuracy in writing are these two processes than those two arithmetical rules in all kinds of computation. Richness and fullness of thought, quickness and fertility of invention, are the immediate fruit of skill in these processes. Two eminent writers in English literature, differing greatly in other respects, exemplify alike the ready command of these analytic processes in unfolding thought, Dr. Barrow and Thomas De Quincey. A close examination of the writings of these authors, and especially of those of Dr. Barrow, will reveal a training of thought, however unconscious, in this direction that is most admirable, and most worthy of imitation by all who covet power in thinking.

§ 88. THE THEME in Division is ever a class, and its parts are denoted by the logical terms species, varieties, individuals.

The first thing, accordingly, to be done in explaining by this process is to obtain a firm grasp of the theme as a generic whole as a class.

The parts of a class — species, varieties, individuals stand in the relation of subordination to one another; species being higher than variety, and lower than class; variety next higher than individuals. There are, of course, manifold intermediate divisions. Natural History, which furnishes the best exemplifications of Division, makes use of the following distinctions, and even others than these, in subdivision of one or other of these named, as sub-class, for there is no necessary limit in thought to them in number: Kingdom, Class, Order or Family, Tribe, Genus, Species, Variety, Individual. This last is the lowest part attainable in Division, and cannot be subdivided.

The theme is either simple, that is a class of outward and sensible objects, or abstract, that is, a class of internal and spiritual objects.

§ 89. The Law of Unity in Division requires that the theme be a single class, and that all the parts in each set be given by one principle of division.

By principle of division is meant the attribute or complement of attributes in respect of which the division is made. This will, perhaps, be better understood by recurring to the logical genesis of all generic forms of thought

the logical account of the origin of all classes in thought. Every such form of thought, every class, then, arises by combining the subjects of different judgments having the same predicate. Thus the class of objects denoted by the term man is formed from judgments having primitively individuals as subjects with a common predicate, John is rational animal, James is rational animal, Peter is rational animal, and then combining these several subjects, and marking the combination by applying a single name, man. Man is now a class including all objects having the attribute of rational animal. To

explain man as such a class would be simply to name the individuals which, as subjects of the several primitive judgments, John, James, Peter,- were combined to form the class. These subjects which are thus combined into a class, it should be remarked, are not limited to individuals; they may be varieties, or species, that is, previous combinations into classes of individual subjects; but, whether individuals or classes they are combined only as they have the same predicate, that is, the same attribute or complement of attributes. The principle of division, now, is this common attribute or complement of attributes. Inasmuch as

the same class of objects may have a great diversity of attributes alike belonging to each of the class, the necessity arises, in order to that distinctness which is the one object of explanation, of fixing upon one or another of these several attributes, and naming the parts the species, the varieties, or the individuals — given by that one. Otherwise the result would be only confusion. Thus man has the attribute of color belonging to the class as a part of the attribute animal; also, the attribute intelligent as a part of the attribute rational. The confused division of the class at the same time into species with reference to color and species with reference to intelligence, giving as the result black men, ignorant men, white men, tawny men, would be no proper explanation. The attribute color should be the principle of division for one explanation; the attribute intelligence for another. Nothing forbids a second division under another principle or attribute subordinate to the first. But in the same single division there should be but one principle. This principle of division is ever to be found in some attribute that was the common predicate in the judgments from which the class was formed by combining the subjects.

The principle of division, then, must be single; and it is ever to be found in some attribute of the theme. After apprehending the theme as a generic whole or class composed of different subjects of such judgments as have a common

predicate, the next thing is to apprehend the particular composite attribute which is to furnish the single principle of division. We have thus the next law, that of Selection in division, as formally stated in the following section.

§ 90. The Law of Selection in Division requires that such attribute of the theme be selected as the principle of division, and that such subdivisions shall be given as shall best subserve the particular design of the discourse.

For different objects in writing, it is obvious, different sets of parts will need to be exhibited. For one purpose, the theme man would be explained through the different species or varieties given by the attribute rational, such as logical, aesthetic, or practical; as thinkers, artists, benefactors; as learned, rude; as civilized, barbarous; for another purpose through species given by the attribute animal, which is another part of the composite attribute rational animal belonging to the class man, such as sanguine, bilious, lymphatic, black, white, tawny, and the like; for another purpose through species given by an attribute of condition, as young, old, African, Asiatic, European, American, Australian, and the like; or still again through species given by an attribute of relation, as citizens, aliens, slaves, freemen, and the like. As the purposes of discourse vary indefinitely, so the principle of division will vary. Aptness to seize the principle of division and to effect the division correctly and fully under it, perhaps more than any other specific capability, marks the degree of ability in the construction of discourse. And this aptness, it may be again remarked, is the result of intelligent practice, precisely as the musician's aptness in using the elements of melody, harmony, modulation, force, is the fruit of careful training. It may be so perfect as to seem instinctive genius; it is nevertheless, as is all skill everywhere, the product of intelligent, discriminating practice.

When it is necessary to carry the explanation to a further degree than the first division, the principle selected for the successive subdivisions may be the same as in the higher division, or it may be different. In the subdivisions, also, the principle of division will vary with the more specific design in that part of the discourse. It is, however, always the design of the discourse, not any thing in the nature of thought, that governs the selection.

§ 91. The Law of Method in Division requires that the subdivisions, or the lower grades of parts, be presented under the higher species to which they respectively belong.

The order of subordination in the different gradations given by division appears in the enumeration under § 88, the highest being kingdom, the next sub-kingdom, then class, sub-class, etc.

The strictest logical method of proceeding in division, and that which should be practiced carefully and thoroughly, is what is called in logic dichotomous, or in two parts, the one of which is complementary of the other. These parts are contradictory to each other and exhaust the theme. Thus a dichotomous division of man, under the attribute rational, is into rational and irrational; intelligent, and non-intelligent or ignorant. Each of these first two parts is then taken as a whole to be divided, and is separated into two parts, the one of which is complementary of the other; and so on successively, as far as the subdivisions are carried. It is frequently the case that language does not furnish suitable expressions for denoting the higher species. In such cases such species are often omitted in the enumeration. Sometimes, too, the purposes of the discourse require only the distinct mention of certain of the parts given in a complete division. Thus we often find divisions with three parts instead of two. Angles, for instance, are completely divided into right, acute, and obtuse. But a strictly logical dichoto