Study Materials for IBPS, Bank Exams : Reasoning - Syllogism
Study Materials for IBPS, Bank Exams : Reasoning - Syllogism
TThe word ‘Syllogism’ is also referred to ‘Logic’. Syllogism is an important section of logical reasoning and hence, a working knowledge of its rules is required on the part of the candidate. Hence, it can be expressed as the ‘Science of thought as expressed in language’. The questions based on syllogism can be solved by using Venn diagrams and some rules devised with the help of analytical ability. With this unique characteristic, this test becomes an instrument of teaching the candidates to follow the rules and work as per the instructions without an error. Here, only the basic concept and rules, which have a bearing on reasoning faculty could alone help. There are some terminology which are used in syllogism.
Proposition
It is also referred to as ‘Premises’. It is a sentence which asserts that either a part of, or the whole of, one sets of objects-the set identified by the subject term in the sentence expressing that sentence either is included in, or is excluded from, another set-the set identified by the predicate term in that sentence.
Types of Proposition
Categorical Proposition: There is relationship between the subject and the predicate without any condition.
Example : I. All beams are logs.
II. No rod is stick.
Hypothetical Proposition: There is relationship between subject and predicate which is asserted conditionally.
Example : I. If it rains he will not come.
II. If he comes, I will accompany him.
Disjunctive Proposition In a disjunctive proposition the assertion is of alteration.
Example : I. Either he is brave or he is strong.
II. Either he is happy or he cannot take revenge.
Parts of Proposition
It consists of four parts.
1. Quantifier: In quantifier the words, ‘all’, ‘no’ and ‘some’ are used as they express quantity. ‘All’ and ‘no’ are universal quantifiers because they refer to every object in a certain set. And quantifier ‘some’ is a particular quantifier because it refers to at least one existing object in a certain set.
2. Subject: It is the word about which something is said.
3. Predicate: It is the part of proposition which denotes which is affirmed or denied about the subject.
4. Copula: It is the part of proposition which denotes the relation between the subject and predicate.
Four-fold classification of categorical proposition: On the basis of quality
and quantity of proposition we can classify them in four categories. To draw
valid inferences it is necessary to have a clear
understanding of the A, E, I, O relationship as given in the table.
1. Universal affirmative or A-type proposition.
2. Universal negative or E-type proposition.
3. Particular affirmative or I-type proposition.
4. Particular negative or O-type proposition.
Rules for Mediate Inference
First introduced by Aristotle, a syllogism is a deductive argument in which
conclusion has to be drawn from two propositions referred to as premises.
Now consider an example.
Statement: I. Vinay is a boy. II. All boys are honest.
Conclusion I. Vinay is honest.
First two sentences I and II are called propositions and the sentence I is called conclusion. This conclusion is drawn from above given two propositions.
Types of Questions Asked in the Examination
There are mainly two types of questions which may be asked under this
1. When premises are in specified form Here premise is in specified form.
Here mainly two propositions are given. Propositions may be particular to
universal; universal to particular; particular to particular; universal to
universal.
2. When premises are in jumbled/mixed form Here at least three or more than
three proposition are given. Here pair of two propositions out of them follow as
same as in specified form.
Type 1 Premises in Specified Forms
Case 1: The conclusion does not contain the middle term Middle term is the term common to both the premises and is denoted by M. Hence, for such case, conclusion does not contain any common term belong to both premises.
Example 1
Statement: I. All men are girls.
II. Some girls are students.
Conclusions I. All girls are men.
II. Some girls are not students.
Solution. Since, both the conclusions I and II contain the middle term ‘girls’ so neither of them can follow. Venn diagram Representation: All possible cases can be drawn by using Venn diagram.
