Reductio ad absurdum
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In logic, reductio ad absurdum, also known as argumentum ad absurdum, apagogical argument, or proof by contradiction, is the form of argument that attempts to establish a claim by showing that followi
Reductio ad absurdum, painting by John Pettie exhibited at the Royal Academy in 1884
Rule of inference
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Rules of inference are ways of deriving conclusions from premises. They are integral parts of formal logic, serving as the logical structure of valid arguments. If an argument with true premises follo
Reductio ad absurdum
…reasoning, as well as in debate. In mathematics, the technique is called proof by contradiction. In formal logic, this technique is captured by an inference rule for reductio ad absurdum. More broadly, proof by contradiction is any form of argument that establishes a statement by arriving at a contradiction…
George Boole (1815–1864) made key contributions to symbolic logic in general and propositional logic in particular.
As one of the founding fathers of modern logic, Gottlob Frege (1848–1925) explored some of the foundational concepts of first-order logic.
The rules of inference in Aristotle's (384–322 BCE) logic have the form of syllogisms.