Western Logic Formal Fallacy Part 1for Kerala PSC
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Complete Video at  Western Logic  Formal Fallacy: Two Negative Premises (Philosophy)
Formal Fallacy

Formal fallacies are those mistakes or errors which occur in the form of the argument.

In other words, formal fallacies concern themselves with the form or the structure of the argument.

Formal fallacies are present when there is a structural error in a deductive argument.

It is important to note that formal fallacies always occur in a deductive argument.
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The Fallacy of Two Negative Premises:

The fallacy of two Negative Premises is also known as the fallacy of Exclusive premises.

This fallacy occurs when a conclusion is drawn from two negative premises.

In Deductive arguments, two negative premises cannot result in a conclusion or cannot have a conclusion.

For example,

No cats are dogs

Some pets are not cats

Therefore, some pets are not dogs


Here, the major premise No cats are dogs is an E proposition which is negative and universal in nature.

The minor premise is Some pets are not cats it is an O proposition which is negative and particular in nature.

So, the two premises, major and minor are both negative in nature.

As a result, no conclusion can be drawn from these two.
Fallacy of Drawing an Affirmative Conclusion from a Negative Premise:

This fallacy occurs when we draw an affirmative or a positive conclusion from a negative premise.

In other words, it means, if one of the premise of an argument is negative, then, the conclusion has to be negative in nature.

It cannot be positive.

For instance, the major premise is negative and the minor premise is affirmative. Hence, the conclusion of a valid syllogism has to be negative.

Similarly, if the major premise is positive, the minor premise is negative, then the conclusion has to be negative.

For Example,

No potters are accountants

Some are girls are potters

Therefore, some girls are accountants


Here, the major premise is an E proposition which is negative in nature.

The minor premise is an I proposition which is positive in nature and the conclusion is also an I proposition and positive in nature.

Hence, this argument is invalid for it commits the fallacy of drawing an affirmative conclusion from a negative premise.
The Existential Fallacy:

The existential fallacy is also known as the fallacy where a particular conclusion is drawn from two universal premises.

In other words, it means, when the two premises are universal (either A or E), then a particular premise is not possible (either I or O).

For example,

All pets are domestic animals

No tigers are domestic animals

Therefore, some tigers are not pets


Here, the major premise of the argument is a universal A proposition.

The minor premise of the syllogism is universal E proposition.

The conclusion of the syllogism is particular O proposition.

This syllogism is invalid because it commits existential fallacy.

No particular conclusion is possible from two universal premises
Important Points

Formal fallacies occur only in deductive arguments.

Formal fallacies occur due to the problem in the form or the structure of the argument.

There are six kinds of formal fallacies.

In Fallacy of four terms, no argument in logic can have more or less than three terms. The only three terms of a valid argument are major term, middle term and minor term.

Undistributed middle term fallacy occurs when the middle term remains undistributed in both the premises, major and minor.

In order to avoid, the fallacy of undistributed middle term, the middle term must be distributed in at least one of the two premises, either major premise or minor premise.

Two negative premises cannot have a conclusion. It is known as Exclusive fallacy and fallacy of two negative premises.

If both the premises are universal then a particular premise is not possible. If it occurs, it is the fallacy, it is called, existential fallacy.
Mcq
1. Fallacy of Exclusive premises is another name of the fallacy
Options:
A. Two negative premises
B. Drawing an affirmative conclusion from a negative premise
C. Existential fallacy
D. None of these
Answer: A
2. In order to avoid, the fallacy of undistributed middle term, the middle term must be distributed in
Options:
A. Both the premises; major and minor.
B. At least one of the two premises, either major premise or minor premise.
C. Only in major premise
D. None of these
Answer: B
3. ___________ fallacy occurs where a particular conclusion is drawn from two universal premises.
Options:
A. Exclusive
B. Existential
C. Both A and B
D None of these
Answer: B
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Manishika