Fallacy

logic argumentation

Definition

Fallacy

A fallacy is an error in reasoning that makes an argument appear valid when it is not.

A fallacy can be formal, arising from a defect in the logical form, or informal, arising from the content, context, or language of the argument.

Formal and Informal

Formal

Definition

Formal Fallacy

A formal fallacy is an error in the logical form of an argument. The conclusion does not follow from the premises, and this can be determined by examining the structure of the argument alone, without reference to its content.

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Informal

Definition

Informal Fallacy

An informal fallacy is an error in reasoning that arises from the content, context, or language of an argument, rather than from its logical form.

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Validity and Soundness

A fallacious argument is not valid. Even if all premises are true, a fallacy means the conclusion is not guaranteed. An argument that is both fallacious and has false premises fails on multiple grounds.