13. Does Abstraction imply Generalisation? 704 14. Discovery of Marks or Characteristics 708 15. Diagnostic Systems of Classification 710 16. Index Classifications 714 17. Classification in the Biological Sciences 718 18. Classification by Types 722 19. Natural Genera and Species 724 20. Unique or Exceptional Objects 728 21. Limits of Classification 730 BOOK VI. CHAPTER XXXI. REFLECTIONS ON THE RESULTS AND LIMITS OF SCIENTIFIC METHOD. 1. Reflections on the Results and Limits of Scientific Method 735 2. The Meaning of Natural Law 737 3. Infiniteness of the Universe 738 4. The Indeterminate Problem of Creation 740 5. Hierarchy of Natural Laws 742 6. The Ambiguous Expression--“Uniformity of Nature” 745 7. Possible States of the Universe 749 8. Speculations on the Reconcentration of Energy 751 9. The Divergent Scope for New Discovery 752 10. Infinite Incompleteness of the Mathematical Sciences 754 11. The Reign of Law in Mental and Social Phenomena 759 12. The Theory of Evolution 761 13. Possibility of Divine Interference 765 14. Conclusion 766 INDEX 773 THE PRINCIPLES OF SCIENCE. CHAPTER I. INTRODUCTION. Science arises from the discovery of Identity amidst Diversity. The process may be described in different words, but our language must always imply the presence of one common and necessary element. In every act of inference or scientific method we are engaged about a certain identity, sameness, similarity, likeness, resemblance, analogy, equivalence or equality apparent between two objects. It is doubtful whether an entirely isolated phenomenon could present itself to our notice, since there must always be some points of similarity between object and object. But in any case an isolated phenomenon could be studied to no useful purpose. The whole value of science consists in the power which it confers upon us of applying to one object the knowledge acquired from like objects; and it is only so far, therefore, as we can discover and register resemblances that we can turn our observations to account.