Definition:Reduction to First Figure/Indirect
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Definition
Indirect reduction to the first figure is a form of the reduction to the first figure method for determining the validity of a categorical syllogism.
This form of the method works backward by supposing that a pattern is not valid, and then deriving a contradiction against a known valid pattern in the first figure.
Hence by Reductio ad Absurdum the pattern is deduced to be valid.
Sources
- 1965: E.J. Lemmon: Beginning Logic ... (previous) ... (next): Chapter $4$: The Predicate Calculus $2$: $4$ The Syllogism