Elementary logic - PDF ebook by Alfred Sidgwick

Elementary logic 1914 by Alfred Sidgwick

Elementary logic
Elementary logic

Books on Logic often begin with what professes to be a definition of Science. And if by a definition all that is meant is a vague general statement of aim or purpose, that is easy to give; the aim of Logic, always and everywhere, is to study the difference between good and bad reasoning. Even the loftiest and least mundane kind of Logic cannot really escape from this purpose; for what interest could there be in ideally perfect truths if no one was ever in the least danger of forgetting them? 

It was the liability of mankind to reason badly that first called Logic into existence, and that still makes the study worthwhile, and to confess its lack of power to detect bad reasoning, or to boast of a lack of interest in doing this, would be fatal to its claims. The general aim of Logic, then, is clear. But real difficulties begin as soon as we try to get the " scope and method " of the Science into its definition, for thereby we run a risk of begging the very important question of whether a particular limitation of scope or a particular method, is a help or a hindrance in achieving the aim. 

There is no general agreement on this point. Indeed that is a mild way of putting it, for we live in times when there is a widespread and growing revolt against certain old methods and old limitations of Logic which have come down to us by tradition. At present they still survive in the examination room, and they still have a harmful in- fluence on some kinds of philosophy, but both in science and in ordinary life they are almost universally reckoned as out of date. 

At the present day, we may safely admit that the best reason for knowing something about the old system is in order to see exactly why modern Logic has been driven to make certain far-reaching departures from it. This book, therefore, attempts to give some account, for beginners, of both the old system and the new. Logic is here treated (i) as a carefully limited subject to get up for an elementary examination; and (2) as a free study of some of the chief risks of error in reasoning. For the former purpose, we must be content to take the traditional doctrines and technicalities as obediently as we can, making light of the serious difficulties in them and treating them mainly as rules and definitions that have to be learned with a particular end in view. On the other hand, for the latter purpose, a different method is necessary. 

Even an elementary treatment of the real risks of reasoning will require a fundamental change of attitude towards the old Logic. Here we must rely on modern ways of thought — modern philosophy, science, and common sense; we must allow free criticism of the assumptions and the self-imposed limitations of the old Logic; and, without refusing to benefit by tradition wherever we find it helpful, we must recognise also its power of hampering and misleading the operations of our reason. 

Desirable as it might be to keep these two modes of logical study separate, it is almost impossible to avoid giving some hints of the deep defects of the old doctrines and the old definitions, in the process of explaining them. But as help against the confusion of the two points of view I shall adopt the plan of spelling the traditional Logic' ' Also Logical, Logically, and Logician.

Introduction vii
Chap. I. The Categorical Syllogism :
1 Our Starting Point. i
2 Subject and Predicate 3
3 The Laws of Thought 7
4 Quality and Quantity 9
5 Some Minor Points 14
Chap. II. The Categorical Syllogism :
Its working
6 The Rules of the Syllogism .... 16
7 Exercises 23
8 Mood and Figure 28
9 Exercises 31
10 Reduction 38
11 Tables 45
12 Examination Questions 48
Chap. III. Other Forms of Deductive Inference
13 Form and Matter of Reasoning .... 64
14 Tense and Modality 67
15 Categorical and Hypothetical Propositions. 71
16 The Conditional Syllogism 74
17 Immediate Inference 85
18 Abbreviated and Compound Arguments ... 90
19 Examination Questions 93
Chap. IV. Further Technicalities
20 Kinds of Term 9^
21 The Predicables 108
22 Division, Definition, and Classification . . • 113
Chap. V. Inductive Inference
23 The Problem of Induction 119
24 Mill's Canons 126
25 The Method of Difference 129
26 The Inferior Methods 131
27 The Deductive Method 138
Chap. VI. The Names of the Fallacies. 142

Chap. VII. The Changed Point of View
28 The Type of Modern Difficulties . . . .152
29 The Change in Logical Method .... 161
Chap. VIII. The Process of Reasoning
30 Verbal and Real Reasoning 171
31 Facts and Their Meaning 173
32 Ambiguous Middle 178
33 Induction and Deduction 185
Chap. IX. The General Conditions of Language
34 Description and Indefiniteness 192
35 Predication and Analogy 198
36 Variations of Purpose 203
37 Distinction and Definition 209
Chap. X. Doctrines and Technicalities. 225
Index 245
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