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# Disjunctive syllogism

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Disjunctive syllogism is a valid, simple argument form:

  Either P or Q.
  Not P.
  Therefore, Q.

Roughly, we are told that it has to be one or the other that is true; then we are told that it is not the one that is true; so we infer that it has to be the other that is true. The reason this is called "disjunctive syllogism" is that, first, it is a syllogism?--a three-step argument--and second, it contains a disjunction, which means simply an "or" statement. "Either P or Q" is a disjunction; P and Q are called the statement's disjuncts.

Here is an example:

  Either I will choose soup or I will choose salad.
  I will not choose soup.
  Therefore, I will choose salad.

Here is another example:

  Either the Browns win or the Bengals win.
  The Browns do not win.
  Therefore, the Bengals win.

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Last edited March 21, 2001 2:17 pm (diff)
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