### Single Idea 9395

#### [catalogued under 4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / c. Derivation rules of PL]

Full Idea

Modus Tollendo Tollens (MTT): Given ¬B and A→B, we derive ¬A as a conclusion. ¬A depends on any assumptions that have been made

Clarification

¬ is 'not'; → means 'implies'

Gist of Idea

MTT: Given ¬B and A→B, we derive ¬A

Source

E.J. Lemmon (Beginning Logic [1965], 1.5)

Book Reference

Lemmon,E.J.: 'Beginning Logic' [Nelson 1979], p.40