vi CONTENTS. 



CHAPTER XXVIII. 



ANALOGY. 



SECTION PAGE 



1. Analogy ; 283 



V s 2. Analogy as a Guide in Discovery . . . . .286 



3. Analogy in the Mathematical Sciences . . . .288 



4. Analogy in the Theory of Undulations . . . . .293 



5. Use of Analogy in Astronomy ...... 297 



6. Failures of Analogy 302 



CHAPTER XXIX, 



EXCEPTIONAL PHENOMENA. 



1. Exceptional Phenomena . . . . . . .306 



2. Imaginary or False Exceptions . . . . . .309 



3. Apparent but Congruent Exceptions . . . . .313 



4. Singular Exceptions . . . . . . . .316 



5. Divergent Exceptions . . , . . . .320 



6. Accidental Exceptions 324 



7. Novel and Unexplained Exceptions . . . . .328 



8. Limiting Exceptions . . . . . . . .331 



9. Real Exceptions to Supposed Laws . . . . .336 

 10. Unclassed Exceptions ..... . 338 



CHAPTER XXX. 



CLASSIFICATION. 



1. Classification - 344 



2. Classification involving Induction ..... 346 



3. Multiplicity of Modes of Classification . . . .348 



4. Natural and Artificial Systems of Classification . . .351 



5. Correlation of Properties . . . . . .353 



6. Classification in Crystallography ...... 359 



7. Classification an Inverse and Tentative Operation . .364 



8. Symbolic Statement of the Theory of Classification . . 367 



9. Bifurcate Classification . . . . . . .371 



10. The Five Predicables 375 



11. Summun Genus and Infima Species . . . . .379 



12. The Tree of Porphyry 381 



13. Does Abstraction imply Generalization ? . . . 389 



14. Discovery of Marks or Characteristics . . . . .394 



15. Diagnostic Systems of Classification ..... 396 

 -. 16. Index Classifications . . . . . . . . 400 



17. Classification in the Biological Sciences . . . .405 



> 18. Classification by Types ... . 411 



19. Natural Genera and Species . . . . . .414 



20. Unique or Exceptional Objects . . . . . .418 



--21. Limits of Classification . 421 



