Western Logic Formal Fallacy Part 1for IAS

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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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#formalfallacy

#affirmativeconclusionofnegativepremise

#majorandminorpremise

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