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| | Fallacies of presumption are fallacies in which an unstated or shaky presumption is made. | | Fallacies of presumption are fallacies in which an unstated or shaky presumption is made. |
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| − | ===Straw man=== | + | ===Contradiction=== |
| | + | A [[contradiction]] is a statement that contradicts its own terms. [[Aristotle]] famously stated that contradictions cannot exist. In any case of a contradition, some of the premises must be false. |
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| | + | Contradictions normally form part of a proof by ''exclusion''. But contradictory arguments are some of the most common flawed arguments, and are closely akin to double standards (see above). |
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| | ===Loaded question=== | | ===Loaded question=== |
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| | An argument that states something as true without offering supporting evidence or attempting to construct a valid argument. The typical form of this "argument" is the "conclusion" of a [[non sequitur]]. | | An argument that states something as true without offering supporting evidence or attempting to construct a valid argument. The typical form of this "argument" is the "conclusion" of a [[non sequitur]]. |
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| − | ====Your theory does not work under my theory, so your theory must be wrong==== | + | ===Circular reasoning=== |
| − | : ''Main article: [[Your theory does not work under my theory, so your theory must be wrong]]''
| + | [[Circular reasoning]] is a form of proof-by-assertion in which one asserts a premise, then asserts a conclusion from that premise (directly or indirectly), and then tries to show that the last conclusion ''supports'' the original premise. |
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| − | The judgment of a theory by the premises and assumptions of another theory, rather than against its own premises and assumptions. This is a variation on proof-by-assertion.
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| | ===Manufacturing facts from a theory=== | | ===Manufacturing facts from a theory=== |
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| | This is yet another form of proof-by-assertion, and is the source of many controversies in modern [[astronomy]], some of them strikingly bitter. | | This is yet another form of proof-by-assertion, and is the source of many controversies in modern [[astronomy]], some of them strikingly bitter. |
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| − | ===Circular reasoning=== | + | ====Your theory does not work under my theory, so your theory must be wrong==== |
| − | [[Circular reasoning]] is a form of proof-by-assertion in which one asserts a premise, then asserts a conclusion from that premise (directly or indirectly), and then tries to show that the last conclusion ''supports'' the original premise. | + | : ''Main article: [[Your theory does not work under my theory, so your theory must be wrong]]'' |
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| | + | The judgment of a theory by the premises and assumptions of another theory, rather than against its own premises and assumptions. This is a variation on proof-by-assertion. |
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| | ===Tautology=== | | ===Tautology=== |
| | A [[tautology]] ([[Greek]] '''ταυτα''' ''tauta'', "these") is an argument that becomes a repetition of a definition. Literally it means "the study of this" or "the study of these." Such an argument, or statement, can prove nothing beyond itself and is useless as a premise. | | A [[tautology]] ([[Greek]] '''ταυτα''' ''tauta'', "these") is an argument that becomes a repetition of a definition. Literally it means "the study of this" or "the study of these." Such an argument, or statement, can prove nothing beyond itself and is useless as a premise. |
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| − | ===Contradiction===
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| − | A [[contradiction]] is a statement that contradicts its own terms. [[Aristotle]] famously stated that contradictions cannot exist. In any case of a contradition, some of the premises must be false.
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| − |
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| − | Contradictions normally form part of a proof by ''exclusion''. But contradictory arguments are some of the most common flawed arguments, and are closely akin to double standards (see above).
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| | ==Fallacies of Ambiguity== | | ==Fallacies of Ambiguity== |