§1. Precise thinking needs precise language 348 §2. Nomenclature and Terminology 349 §3. Definition 352 §4. Rules for testing a Definition 352 §5. Every Definition is relative to a Classification 353 §6. Difficulties of Definition 356 Proposals to substitute the Type (p. 356) §7. The Limits of Definition 357 §8. The five Predicables 358 Porphyry's Tree (p. 361) §9. Realism and Nominalism 364 §10. The Predicaments 366 CHAPTER XXIII DEFINITION OF COMMON TERMS §1. The rigour of scientific method must be qualified 369 §2. Still, Language comprises the Nomenclature of an imperfect Classification, to which every Definition is relative; 370 §3. and an imperfect Terminology 374 §4. Maxims and precautions of Definition 375 §5. Words of common language in scientific use 378 §6. How Definitions affect the cogency of arguments 380 CHAPTER XXIV FALLACIES §1. Fallacy defined and divided 385 §2. Formal Fallacies of Deduction 385 §3. Formal Fallacies of Induction 388 §4. Material Fallacies classified 394 §5. Fallacies of Observation 394 §6. Begging the Question 396 §7. Surreptitious Conclusion 398 §8. Ambiguity 400 §9. Fallacies, a natural rank growth of the Human mind, not easy to classify, or exterminate 403 QUESTIONS 405 LOGIC CHAPTER I INTRODUCTORY