To follow the chain of thought in the paragraph, it is necessary to see clearly the relation of each thought as expressed in the sentence to the preceding and succeeding thoughts in order that the development of the topic may be clear, and that the pupil may grasp the subject in its entirety. In teaching the pupil to get the whole thought in the paragraph, it is necessary to consider the whole topic treated in the paragraph; that is, to study the unity of the paragraph; and also to consider the relation of each thought to the one central topic; that is, the principle of paragraph coherence. Thus, in the effort to teach the pupil how to get the thoughts of others by reading, the essential principles of composition are absolutely necessary. In a similar manner all the principles of narration, description, exposition, and argumentation may be developed inductively from the reading. By seeing the application of the rhetorical principles in literature, the pupil comes to realize their importance in effective writing, and is impressed by the varied forms of their application as he is not likely to be by selected examples isolated from their context, in text-books. 7. Use of Text-book If the principles of composition may be developed from the masterpieces that are studied in class, the question naturally suggests itself, “Is it necessary to have a text-book at all in studying the principles of rhetoric and composition?” It is entirely possible to teach composition successfully without a text-book, but owing to difficulties in the organization of the schools, and the not infrequent change of teachers, it is often desirable for the sake of uniformity of work to make use of a text-book. It is also convenient, even where these difficulties do not exist, to have a good text-book to which the teacher may direct the pupil for a detailed statement of the principles after they have been developed and exemplified in the reading; that is, to use it as a reference book. In order that it may be used thus for reference, the text-book selected should take up the principles of composition and the forms of discourse in a logical manner, treating each fully and systematically in a separate division. Text-books of this character can be used throughout the first two years at least, and some of them are sufficiently complete to supply all the material needed for four years’ study of composition.