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Affirmative conclusion from a negative premise

Incorrect application of a syllogism by deriving an affirmative (positive) conclusion from a negative premise.

For example Open in Syllogism-Finder App:

All squares are rectangles.
No circles are squares.
Therefore, All circles are rectangles.

Description

One fundamental rule for all syllogistic and similar inferences is that if one of the premises is a negative, the conclusion can only also be a negative statement. There are no valid syllogism forms that contradict this rule. Trying to construct one is a formal fallacy.

Furthermore, if both premises are negative, no conclusion can be inferred at all (Fallacy of exclusive premises).

See also

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