VALIDITY and INVALIDITY
TEST #1

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Your answer is incorrect.

We must have food and water.

We don't have food.

Therefore, we do not have water.

This argument is invalid . It is a disjunctive syllogism and the major premise must present two alternatives. As stated there are no alternatives presented. To be valid the major premise would have to say "We must have food or water." Even then, however, the conclusion would have to say we do have water to be valid.

In addition, in a valid disjunctive syllogism, if the minor premise rejects an alternative the conclusion must accept the other alternative, but in this example both the minor premise and conclusion reject alternatives.

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