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affirming a disjunct

The invalid form: P or Q; P; so not Q.

Affirming a disjunct is the formal fallacy: P or Q; P; therefore not Q. It imitates disjunctive syllogism but asserts a disjunct instead of denying one. Because logic's "or" is inclusive, both disjuncts may be true.

Examples

  • "The fuse blew or the bulb burned out. The fuse blew. So the bulb didn't burn out." Both may have failed.

See also

disjunctive syllogism inclusive or formal fallacy
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