t is important to be able to distinguish between a valid argument and a sound ar

Question

t is important to be able to distinguish between a valid argument and a sound argument. A valid argument is one in which the conclusion follows necessarily from the premises, such that if the premises are true, the conclusion must also be true. A sound argument is one that is valid and the premises are true (hence the conclusion is also true). Here is an example of a valid deductive argument with true premises and a true conclusion:

Premiss 1: If the North won the Civil War, then the slaves were freed.

Premiss 2: The North won the Civil War.

Conclusion: Therefore, the slaves were freed. But consider this argument:

Premiss 1: If the South won the Civil War, then the slaves were freed.

Premiss 2: The South won the Civil War.

Conclusion: Therefore, the slaves were freed.

Here, the argument is valid even though both premises are false and the conclusion is true. It is valid, because if the premises were true, then the conclusion would be true also. The conclusion still follows from the premises. But, it is not sound because at least one of the premises is false

. Are the following valid? Are these arguments sound?

Premiss 1: All seniors are talented (False)

Premiss 2: All talented people are ugly (False)

Conclusion: All seniors are ugly (False)

Premiss 1: All ugly people are seniors (False)

Premiss 2: All seniors are insightful (False)

Conclusion: All ugly people are insightful (True)

Premiss 1: All ugly people are insightful (True)

Premiss 2: All talented people are ugly (False)

Conclusion: All talented people are insightful (True)

Are the three arguments in the bottom of the handout valid? (Why or why not?)

Are the three arguments in the bottom of the handout sound? (Why or why not?)

Explanation / Answer

Premiss 1: All seniors are talented (False)

Premiss 2: All talented people are ugly (False)

Conclusion: All seniors are ugly (False)

Solution: It is valid as it is logically valid and so it in the right form.

It is not sound as both of the premises as well as conclusion is false.

Premiss 1: All ugly people are seniors (False)

Premiss 2: All seniors are insightful (False)

Conclusion: All ugly people are insightful (True)

Solution: It is valid as it is logically valid and so it in the right form. It is not sound as its premises is false.

Premiss 1: All ugly people are insightful (True)

Premiss 2: All talented people are ugly (False)

Conclusion: All talented people are insightful (True)

Solution: It is valid as it is logically valid and so it in the right form. It is not sound as its premises is false.

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