n.
In logic , a type of inference or argument that purports to be valid, where a valid argument is one whose conclusion must be true if its premises are true (see validity ).
Deduction is thus distinguished from induction , where there is no such presumption. Valid deductive arguments may have false premises, as demonstrated by the example: "All men are mortal; Cleopatra is a man; therefore, Cleopatra is mortal." Invalid deductive arguments sometimes embody formal fallacies (i.e., errors of reasoning based on the structure of the propositions in the argument); an example is "affirming the consequent": "If A then B; B; therefore, A" (see fallacy; formal and informal ).