CBSE Book Class 11 Philosophy The Nature and Subject matter

The Nature and Subject Matter of Logic

LOGIC: An Introduction

Logic essentially has to do with reasoning of a particular sort, viz., inference. It is, in general, concerned with reflective thinking that is a thinking process which consists of going from one or more stated reasons, evidences or premises to a stated conclusion. Since every rational inquiry depends on logic, so it is very important that we know what follows from what. The gamut of reasoning is very big which attracts both psychologists and logicians alike; while the former is interested in the actual reasoning processes the latter is only interested in the correctness of the completed processes. Thus, the aim of logic is to make explicit rules and methods by which correct inferences or good thinking be distinguished from the incorrect ones rather than to study actual reasoning processes.

Logic provides meaning to any intelligible human linguistic discourse. It imparts and assesses the element of rationality in any completed reasoning process. While imparting rationality it enhances our stock of knowledge whereas in assessing rationality in its own technical way, it shows the utility or futility of any discourse. It is the backbone of any scientific literature. It is both a science and an art. It is science in so far as it provides consistency to what one believes. If there is no consistency in what one believes, then the entire talk of logic falls flat and the basic purpose of language, viz., communication is defeated. Further, it shares two prominent features with science which are as follows:

(i). It is an organized and systematic knowledge,

(ii). Its laws are universally applicable.

It is an art because its worth lies in winning strategies in the game of arguments. Awareness of logical principles and techniques leads to good thinking which helps us to distinguish fact from fancy. Either way logic is much more than a learning experience. Thus, logic can decidedly be defined as 'the science of inference'.

Inference is a psychological process that goes on in mind. It consists of going from one or more stated reasons or premises (sensory-evidence) to a stated conclusion of some kind. The linguistic counterpart of any inferential process is called an argument. This shift from a mental process to a linguistic counterpart is essential because most of what we believe, we have inferred. We express our beliefs through statements which are the building blocks of arguments. Thus, every argument reflects the underlying inferential process. When the passage from premises to conclusion is justified, the argument is called valid. When the passage is not justified, the argument is called invalid or fallacious.

The Nature and Subject Matter of Logic

From the above it is clear that the logician's primary interest is with arguments. His task is twofold:

(i) Finding criteria for distinguishing good from bad arguments, and

(ii) Discovering techniques for constructing good arguments.

Types of Logic

An argument is a set of propositions out of which one is the conclusion which is inferred and the rest are premises. In other words, an argument is a set of propositions barring one which is regarded as its conclusion. The following are examples of arguments:

(i) All birds are mammals and all sparrows are birds. So, all sparrows are mammals.

(ii) All communists are opposed to private property. All socialists are opposed to private property.

Therefore, all socialists are communists.

A question arises as to what is the connexion between the premises and the conclusion. The reply to this question is that there is an evidential connexion between the two. The premises provide evidential support or justification for the conclusion. It is for the logician to evaluate whether the given evidence supports the conclusion or not. It is on the basis of this intended evidential relationship that we divide logic into two types, viz., deductive and inductive.

Every argument necessarily has two features. It has (i) a structure and (ii) a content. These two features can be best understood from the following figures.

P1 Evidence P1 Evidence

P2 Evidence P2 Evidence

Pn Evidence Pn - 1 Evidence

C: X is or is not the case. C: X may be or may not be the case.

(Fig - 1) (Fig - 2)

Figure 1 presents premises ( P1 to Pn) as evidences leading to the conclusion as X is or X is not the case. Here, the evidential connection between premises and conclusion is based on necessity; thus the argument is deductive. In deductive argument the premises imply the conclusion. The deductive argument can be termed as valid or invalid when tested by various logical methods. Since deductive arguments are not concerned with the subject matter of the propositions which occur in it, they are not content-sensitive. They are actually those general moulds of thinking that are capable of generating infinite number of likewise arguments. That is to say, one valid argument-form is capable of generating innumerable likewise arguments. Validity as a logical virtue is preserved in all the subsequent arguments. A valid deductive argument can never have true premises and a false conclusion; so it is truth preserving.

Figure 2 presents premises (P1 to Pn - 1) as evidences but leaving one instance out irrespective of the total evidential instances. Subtracting this single instance from the total number of instances makes the argument-form probable. Here, the evidential connexion between the premise and conclusion is based on probability; so the argument is inductive. It also shows the limitations of scientific laws which are widely confirmed workable hypotheses. These hypotheses, though open to revision, are always relative to the evidence. That is why scientific laws can never be absolute.

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