ELEMENTARY LOGIC

CHAPTER I.-INTRODUCTION

1. DEFINITION OF LOGIC.-Logic may be defined as the science of the laws of thought and the art of using them. This definition serves as an indication of the nature of logic, though it must be regarded as merely preliminary and tentative. Our whole course is to show what ground logic covers, and also how its laws are to be made of practical use.

We must pause to consider the difference between science and art. The former teaches us to know, the latter to apply our knowledge to concrete situations. Science gives us abstract statements of laws, while the corresponding art shows how these abstract formulas are to be made applicable to practical needs. Thus the science of psychology includes statements of laws governing the accumulation and organization of knowledge, the art of teaching puts these scientific principles to use in school-room practice. The science of logic is sometimes called Pure Logic, the art of logic Applied Logic. In this book no hard-and-fast distinction will be made between the two aspects of the subject, though the discussion of laws will emphasize the "pure" side, the practice of the various exercises the "applied" side.

A moment's explanation is needed to dispose of the word "thought" as employed in the above definition. Thought, as used in this connection, means any effort to determine the meaning or implication of a present form of experience. Those parts of our experience that hold our attention are worked up into ideas or thoughts which prompt our reasoning powers to bring them into relation with other ideas or thoughts. This attempt to organize our ideas is the work of intellect or reason. In order to prevent intellect's going astray in the heat of enthusiasm to extend our knowledge beyond our present, momentary experiences, we have to see to it that the procedure follows certain principles of valid reasoning set forth in logic.

Sigwart, the German logician, indicates the need and function of logic very clearly in the following passage:

If we consider the nature of our thought, we find that an important part of it is engaged in the attempt to arrive at propositions which are certain and universally valid, but that it frequently fails to do this when left to its natural development. Hence arises the problem of ascertaining the conditions under which this object can be attained, and of determining in accordance with those conditions the rules to be followed in its attainment. The solution of this problem would place us in possession of a technical science of thought, directing us how to arrive at certain and universally valid propositions. Such a science we call Logic.1

2. RELATION TO OTHER SCIENCES.-Logic is closely related to and in a measure dependent upon the sciences of grammar, rhetoric, and psychology. Logic is concerned with the meanings of our various thoughts. We

1 Sigwart, Logic (Eng. tr.), Vol. I, p. 1.

never think without intending or meaning something that points beyond the thought considered as a mere mental process. These meanings are useful to us as guides to various kinds of action. If I go through the psychological process of noticing that snow is on the ground, if I summon up from past experience the interpreting thought that snow is cold, if I conclude that consequently it will be worth while to wrap up well before venturing out, it is clear that I reach this conclusion only in view of contemplated action. But I expect such a conclusion to guide not only my own action, but also the actions of other members of my family. In other words, though I may not in the first instance give oral expression to the conclusion that I must wrap up well before going out, I yet feel that when I choose to express it in language it will gain the assent of others. The thought has meaning for my action just in so far as, if expressed, it would also have a compelling force in controlling the actions of others. This meaning-value of a reasoning process is what we intend when we say that it is true.

Before my meaning can be put to the test of assent by others, it must have a language form. This language form must accomplish two results: first, it must state exactly what I think, so as to defy my own criticism; second, it must stimulate in other minds essentially the same thought that I seek to convey. Both grammar and rhetoric lay down principles governing the accurate statement of thought, and from these principles logic must borrow when applying the test for meaning. Grammar teaches the forms and syntactical relations of

words. Forms and relations express modifications and shades of meaning. Logic assumes grammatical science in so far as such science is the basis of meaning. Rhetoric is in part an advanced grammar, in part a science of style. Those principles of rhetoric which are concerned with rendering the meaning clear are adopted as a basis of logic. But that part of rhetoric which treats of style has no logical value; for logic is continually engaged in stripping off the outer adornments of style to get at the framework of meaning, which they half reveal and half conceal.

Logic is an expression of certain mental processes. These are analyzed, described, and explained in psychology. Hence logic must resort to psychology for these analyses, descriptions, and explanations. The difference between psychology and logic is that the one is interested in the intellectual processes merely as such, while the other is interested in their results.

The obligation which logic owes to certain sciences is more than repaid by the fact that it contributes to all sciences their mode of procedure. Every kind of scientific exposition, be it book or recitation, lecture or experiment, must be logical to be fruitful. Logic thus offers the key to success or failure in method, and according as scientific writings succeed or fail are they examples of good or bad logic.

3. NATURE OF THE LAWS OF THOUGHT.-The word law is used in so many ways that we need to consider its meaning in the phrase, laws of thought. By law we usually mean either an artificially devised enactment under the control of human will, or else a uniform mode

of nature's operation, which man discovers and states, but cannot control. An example of the one are the laws passed by the Fiftieth Congress; of the other, the law of falling bodies. Laws of thought are in the class of natural laws. They were discovered and expressed in language by man, but cannot be made and unmade_ at his bidding. Our acts may bring natural laws into conflict-with a usual consequence of disaster to oneself; as when a man bent on suicide brings about a situation where the laws of his physical well-being conflict with those of falling bodies by projecting himself from a third-story window to the pavement below. One can never annul them as can the legislator the man-made laws on our statute-books. The natural laws governing our logical thinking are sometimes called regulative, because the strict observance of them forestalls wrong conclusions. We often find that they conflict with certain other natural laws governing our mental behavior. Thus there is a general psychological principle to the effect that an unusual stimulus in the way of sudden shock produces very strong emotions of joy, fear, or anger, as the case may be. A mind which is in this state is prone to act without due deliberation, without regard to the laws of logic, and hence to arrive at insane conclusions. Here is an instance of conflict between these various natural laws within the psychological sphere. In a word, it may be said that natural laws of thought are regulative, like those of health. When discovered and obeyed, our thinking goes well; when either wittingly or unwittingly ignored, our thinking gets into the most inextricable tangles.