CHAPTER VI.

THE INDIRECT METHOD OF INFERENCE.

1. The Indirect Method of Inference 81

2. Simple Illustrations 83

3. Employment of the Contrapositive Proposition 84

4. Contrapositive of a Simple Identity 86

5. Miscellaneous Examples of the Method 88

6. Mr. Venn’s Problem 90

7. Abbreviation of the Process 91

8. The Logical Alphabet 94

9. The Logical Slate 95

10. Abstraction of Indifferent Circumstances 97

11. Illustrations of the Indirect Method 98

12. Second Example 99

13. Third Example 100

14. Fourth Example 101

15. Fifth Example 101

16. Fallacies Analysed by the Indirect Method 102

17. The Logical Abacus 104

18. The Logical Machine 107

19. The Order of Premises 114

20. The Equivalence of Propositions 115

21. The Nature of Inference 118