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Some common informal fallacies. Fallacies of: 1. Presumption2. Ambiguity3. Grammatical Analogy.

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Presentation on theme: "Some common informal fallacies. Fallacies of: 1. Presumption2. Ambiguity3. Grammatical Analogy."— Presentation transcript:

1 Some common informal fallacies

2 Fallacies of: 1. Presumption2. Ambiguity3. Grammatical Analogy

3 1.Presumption a) Begging the question b) Complex question c) False dichotomy d) Suppressed evidence

4 2.Ambiguity a) Equivocation b) Amphiboly 3.Grammatical Analogy a) Composition b) Division

5 1.a) “Begging the question” occurs when there is an attempt to hide the fact that a certain premise may not be true. Additionally, the argument begs the question at issue; it asks that the statement to be proved be granted beforehand. Two requirements: i. The argument must be valid. ii. Some form of phraseology must be used to conceal the questionably true character of a key premise.

6 Ex. 1 Capital punishment is justified for the crimes of murder and kidnapping because it is quite legitimate and appropriate that someone be put to death for having committed such hateful and inhuman acts. The argument is phrased such that the premise and conclusion say the same thing in 2 slightly different ways. - “justified” means “legitimate and appropriate” - “capital punishment” means “being put to death”

7 p→qReq’t 1. Valid form: p___‘Affirming the antecedent’ q - The only question is whether the premise is true.

8 Ex. 2 Murder is morally wrong. This being the case, it follows that abortion is morally wrong.

9 Problem: The questionably true premise is completely ignored: “Abortion is a form of Murder” Valid form:All A is M. All M is W. All A is W.


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