Class 11 Logic And Philosophy Chapter 8 Categorical Syllogism

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Class 11 Logic And Philosophy Chapter 8 Categorical Syllogism

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Categorical Syllogism

Chapter – 8

LOGIC & PHILOSOPHY

VERY SHORT TYPES QUESTIONS AND ANSWERS

1. Find out the correct answer : 

(a) Is it true that in a immediate inference there are

premises? 

Ans : No, it is false.

(b) Obversion is an immediate inference. Is it true? 

Ans : Yes, it is true.

(c) How many premise are required to draw a conclusion immediate inference?

Ans : Only one premise.

(d) Is it true that in a categorical syllogism there is only one middle term? 

Ans : Yes, it is true.

(e) In a categorical syllogism the middle term must be distributed at least once? 

Ans : Yes. 

(f) Which term determine the figure of a syllogism. Ans : Middle term.

Ans :Middle term.

(g) How many valid moods are there is the third figure? 

Ans : Six valid moods. 

(h) ‘In the first figure the major premise must be particular proposition’- is it true? 

Ans : It is false.

(i) What is the name of the predicate of the conclusion of a syllogism? 

Ans : Major term.

2. Define : 

(a) Conversion.

Ans : Conversion is a kind of Immediate Inference, in which there is a legitimate transposition of the subject and the predicate of a proposition.

(b) Obversion.

Ans : Obversion is a kind of Immediate Inference, in which there is a change in the quality of the given proposition, while its meaning remains unchanged.

(c) Syllogism.

Ans : A syllogism is a form of mediate deductive inference, in which the conclusion is drawn from two premises, taken jointly.

(d) Minor term. 

Ans : The subject of the conclusion is called the Minor term.

(e) Middle term.

Ans : The terms which occurs is both the premises, but does not go in the conclusion is called the Middle term.

(f) Major term.

Ans : Inference is the process of passing from one or more propositi to another, which is justified by term, and the product in calli an inference.

(h) Material obversion.

Ans : Material obversion is the process of drawing obverse inference which are justified only on an examination of the matter of th À proposition.

(i) Figure of syllogism.

Ans : Figure is the form of a syllogism as determined by the position of the middle term in the premises.

(j) Mood of syllogism.

Ans : Mood has been define as the form of a syllogism, as determined by the quality and the quantity of the constituent premises.

SHORT & LONG TYPES QUESTIONS ANSWERS

3. Answer the following :

(a) What is immediate inference ?

Ans : Immediate inference is a kind of deductive inference, in which the conclusion follows from only one premise.

(b) Can a proposition be converted simply?

Ans : A proposition can be said to be converted simply . In simple conversion, the quantity of the converse is the same as the quantity of the converted. If we can draw an A proposition from an Á proposition by conversion, in ordinary sense this is not possible., Because if the converse be an A proposition, its subject will be distributed though that term which is the predicate of the convertend, is not distributed therein. But, certain exceptional kinds of a A proposition which the subject and the predicate have the same denotation, there simply conversion of a proposition is possible.

For example : Everest is the highest mountain. (A)

The highest mountain is Everest. (A) 

(c) What is material obversion?

Ans : Material obversion is the process of drawing obverse inference which are justified only on an examination of the matter of the proposition.

(d) How many propositions are there in a logical syllogism? Explain.

Ans : In a logical syllogism, there are three propositions viz., two given propositions and the proposition which is inference from the given propositions.

The inferred propositions is called the conclusion, and the two given propositions, from which the conclusion is drawn, are called the premises. The major term occurs in Major Premise and the minor term occurs in Minor Premise. In a syllogism, the major premise in given first, the minor premise comes next and last of all comes the conclusion.

(e) How many term are there in a logical syllogism? Explain. 

Ans : There are three different terms in a logical syllogism, each of which occurs twice. The predicate of the conclusion is called the major term, the subject of the conclusion is called the Minor term and that term which occurs in both the premises, but does not occur in the conclusion, is called the Middle term. The Major and Minor terms are called Extermes, to distinguish them from the Middle term.

4. Distinguish between :

(a) Immediate inference and mediate inference. 

Ans : Immediate Inference is a kind of deductive inference, in the conclusion follows from only one premise. For example No men are perfect No Perfect beings are men In Mediate Inference, the conclusion follows from more than proposition. The form of Mediate Inference is called ‘Syllogism’.

For example : No perfect beings are mortal

                       All men are mortal

               ∴         No men are perfect beings.

(b) Simple conversion and conversion per accidens. 

Ans : In simple conversion, the quantity of the converse is the same the quantity of the convertend, ic, to say if the convertend universal, the converse also is universal, and if the converter be particular, the converse is also particular. Thus E proposition and I propositions are converted simply.

In conversion per accidens, the quantity of the converse different from the quantity of the convertednic, the converter is universal but the converse is particular. Thus A proposition which yield I propositions as conclusion, are converted accidens.

5. Give example :

(a) Simple conversion. 

Ans : No man is perfect (E)

         No perfect beings are men (E)

(b) Material Obversion.

Ans : War is productive of evil

         Peace is productive of good.

(c) Fallacy of Four terms.

Ans : My hand touches the table.

        The table touches the floor. 

        My hand touches the floor.

(d) Syllogism.

Ans : All men are mortal

         Socrates is a man. 

         Socretes is mortal.

(e) Conversion per accidens.

Ans : All men are mortal. (A)

         Some mortals are men (1)

 (f) Obversion-

Ans : All men are mortal (A)

         No men are non-mortal

6. Short notes : 

(a) Figure.

Ans : Figure is the form of a syllogism as determined by the position of the middle term in the premises.

There are four figures of syllogism : 

(i) First Figure :- In the first figure, the middle term is the subject in the major premise and predicate in the minor premise.

(ii) Second Figure :- In the second figure, the middle term is the predicate in both the premises.

(iii) Third Figure :- In the third figure, the middle term is the subject in both the premises.

(iv) Fourth Figure :- In the fourth figure, the middle term is the predicate in the major premise and subject in the minor premise.

(b) Copula.

Ans : A proposition consists of three parts, viz, two terms and the sign of relation between these two terms. This sign of relation between

the subject term and the predicate term is known as the copula, The copula is sign of affirmation or denial. In the proposition “Man is mortal’, the subject term is ‘man’, the predicate term is *mortal’, while ‘is’ stands as the sign of relation constituted the copula. The copula may be affirmative or negative. But it should be in the present tense of the verb to be.

(c) Mood.

Ans : Mood has been defined as the form of syllogism, as determined by the quality and the quantity of the constituent premises. As there are four kinds of propositions and every syllogism has two premises. So, we have sixteen moods in each figure. There are all together four figures – so we have 16×4 =64 possible moods. Again, if we take the conclusion with the premises, then there are three propositions and therefore each of the 64 combinations have four forms. Thus is all the four figures, there are 64 02154 = 256 moods. But all of these moods are not valid. Only those combinations which yield valid conclusions are valid moods. In this sense, only 19 moods are valid.

(d) Middle term.

Ans : The term which occurs in both the premises, but does not occur in the conclusion, is called the Middle term. The Middle terms occurs in both the premises and the common element between them. The conclusion seeks to establish a relation between the major term and the minor term. 

The middle term performs the function of an intermediary, a person who, as it were, is known to both these strangers, and brings about an introduction between these strangers. Thus in the major premise, the major terms is compared with the middle term, and in the way. ultimately in the conclusion a relation is established between the major term and the minor term. The middle term is a mediating term by which we pass from premises to conclusion.

(e) Material obversion.

Ans : Bain describes a process of inference, which is known as Material obversion. It is a process in which, “there are obverse inferences justified only on an examination of the matter of the proposition.” For example ;

                      Knowledge is good

                      Ignorance is bad.

Bain recognises that these inference are entirely different from the formal inference of obversion. None of the rules of obversion has been followed, here. In obversion, the subject of the obverse is the same as the subject of the given proposition, but in material obversion they are contraries. In obversion, the predicate of the obverse is the contradictory of the predicate of the obvertend, whereas, in material obversion the predicates are also contraries. Again, is material obversion the quality is the same, but is obversion the quality of the conclusion is the opposite of the quality of the given proposition. These inferences are not formal inferences, but material inferences based on experience and knowledge and so it is outside the scope of Deductive Logic.

(f) Fallacy of four terms.

Ans : According to the General Rule of Categorical Syllogism- every syllogism must contain three, and only three terms.’ So, we see that a syllogism consists of three terms- the major term; the minor terms and the middle term, each of which occurs twice. A violation of this rule gives rise to an error of fallacy known as the fallacy of four terms.

(g) Structure of a syllogism.

Ans : A syllogism consists of three proposition, viz, two given propositions and the proposition which is inferred from the given propositions. The inferred proposition is called the conclusion and the two given propositions from which the conclusion is drawn are called the premises.

Each proposition consists of two terms. Therefore, a syllogism consists of three propositions should consist of six terms. But find that a syllogism consists of three terms, each of which occur twice.

The predicate of the conclusion is called the Major Term, the subject of the conclusion is called the Minor Term and that ter which occurs in both the premises, but does not occur in the conclusion is called the Middle term

The Middle term occurs in both the premises and in the common element between them. The conclusion seeks to establish a relation between the major term and the minor terrì. In the major premise, 7. the major term is compared with the middle term and in the minor premise, the minor term is compared with the middle term and A thereby in the conclusion a relation is established between the major and the minor term.

For example :

                       All men are mortal 

                      All kings are men

              ∴     All kings are mortal.

The term “mortal’ is the major term, the term “kings’ is the minor term and the term ‘men’ is the middle term. The first premise ‘All men are mortal is the major premise, the second premise, ‘All kings are men’ is the minor premise. And the last proposition All kings are mortal’ is the conclusion.

The symbol M stands for the Middle term, S stands for the Minor term, and P stands for the Major term.

(h) Conversion by negation.

Ans : According to the rule ‘O’ proposition can not be converted. Some lovicians seek to convert an ‘O’ proposition, by a process of conversion by negation. They first of all reduce the ‘0’ proposition to an T proposition, by transferring the sign of negation to the predicate and then convert it. Thus –

                Some S is not P.(O) 

        ∴      Some S is not, P.(I) 

        ∴      Some not-P is S. (I)

But the form of argument cannot be called conversion at all. Because, the conclusion is different from that of the given proposition. Again, the subject of the conclusion is not the predicate of the premise, but its contradictory.

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