Saturday, May 29, 2010

Fallacy: Affirming a Disjunct

This formal propositional fallacy occurs when it is concluded that one disjunct must be false because the other disjunct is true, when they may both be true.

Logical Form:
A or B
Therefore, it is not the case that B

Counter Example:
Lassie is a dog or Lassie is a mammal
Lassie is a mammal
Therefore, Lassie is not a dog


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