What is Logic Reasoning?

LOGIC is the ’science of thought as expressed in language. This means that the questions on logic are to be solved as per the information given without any concern of the formal validity or truth of the statements i.e; conclusion should follow directly from the statements given. With this unique characteristic, the Logic Test becomes an instrument of teaching the candidates to follow the rules and work as per the instructions without an error. Thus, it prepares the mind for all types of reasoning practices and teaches how to detect and avoid mistakes in the same.

LOGICAL REASONING

In Logic, any statement is termed as the Proposition. Thus, a Proposition is a statement expressing certain relation between two or more terms,
analogous to a sentence in grammar. The Proposition consists of three parts:

1. Subject: The Subject is that about which something is said.
2. Predicate: The Predicate is the part of the Proposition denoting that which is affirmed or denied about the subject.
3. Copula: The Copula is that part of the Proposition which denotes the relation between the Subject and the Predicate.

Consider the Proposition-

‘Man is cultured’.
Here an information is given about the man. So ‘Man’is the Subject.

‘Cultured’ is the quality affirmed for this Subject. So it is the Predicate. ‘is’ denotes the relation between the Subject and the Predicate. So, it is the Copula.

Four Fold Classification of Propositions:
‘Propositions’ can be classified into four types:

1. Universal Affirmative Proposition (denoted by A) : It distributes only the subject i.e., the Predicate is not interchangeable with the subject while maintaining the validity of the Proposition. e.g.,

All men are animals. This is Proposition A since we cannot say ‘All animals are men.’

2. Universal Negative Proposition (denoted by E) : It distributes both the Subject and the Predicate i.e., an entire class of predicate term is denied to the entire class of the subject term, as in the proposition. e.g.

No boy is intelligent.

3. Particular Affirmative Proposition (denoted by I) : It distributes ‘neither the Subject nor the Predicate. e.g.

Some people are foolish.

Here, the subject term ‘Some people’ is used not for all but only for some men and similarly the predicate term ‘foolish’ is affirmed for a part of subject class. So, both are undistributed. 4. Particular Negative Proposition (denoted by 0) :

It distributes only the Predicate. e.g., Some animals are not wild. Here the subject term ’some animals’ is used only for a part of its class and hence is undistributed while the predicate term ‘wild’ is denied in entirety to the subject term and hence is distributed. These facts can be summarized as follows:

Proposition

Type

(a) (A) distributes subject only.
(b) (E) distributes subject and predicate both.
(c) (I) distributes neither.
(d) (0) distributes predicate only

All S is P.
No S is P.
Some S is P.
Some S is not P.

SYLLOGISM: In Logic, we are required to deal with a particular type, termed as Syllogism. It was introduced by Aristotle.
In Syllogism, a conclusion has to be drawn from two propositions, referred to as the Premises.

Example:
1. All lotus are flowers.
2. All flowers are beautiful.
3. All lotus are beautiful.

Clearly, the propositions 1 and 2 are the Premises and the proposition 3, which follows from the first two propositions, is called the Conclusion.
Term: In Logic, a TERM is a word or a combination of words, which by itself can be used as a subject or predicate of a proposition.

Syllogism is concerned with three terms:

1. Major Term: It is the predicate of the conclusion and is denoted by P (first letter of ‘Predicate.)
2. Minor Term: It is the subject of the conclusion and is denoted by S (first letter of ‘Subject’).
3. Middle Term: It is the term common to both the premises and is denoted by M (first letter of ‘Middle’).

Note that the middle term does not occur in the conclusion.

Example:
Premises:
1. All dogs are animals.
2. Tiger is a dog.

Conclusion: Tiger is an animal.

Here, ‘animal’ is the predicate of the conclusion and so, it is the Major Term, P. ‘Tiger’ is the subject of the conclusion and so, it is the Minor Term, S. ‘Dog’ is the term common to both the premises and so, it is the Middle Term, M. Major and Minor Premise: Of the two premises, the major premise is that in which the middle term is the subject and the minor premise is that in which the middle term is the predicate. . Rules for deriving the conclusion:

1. The conclusion does not contain the middle term.

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