Explain the meaning of invalid argument form. Provide real-life examples.?

Question

Explain the meaning of invalid argument form. Provide real-life examples.

Answer 1

Analyze Bush's argument for starting the war in Iraq. It is invalid for two reasons: False assumptions and Invalid Inference.

Answer 2

A valid argument is an argument where the conclusion cannot be false if the premises are true.

It is important to keep the notion of validity seperate from the notion of soundness. An argument can be completely unsound and still be valid. For example:

If there is WMD in Iraq, we must invade
There is WMD in Iraq
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We must invade

This is a perfectly valid argument, but it is unsound. It is unsound because both premises are false. It is valid because IF both premises were true, then the conclusion would have to be true as well.

A sound argument is an argument that is valid AND has true premises.

Answer 3

All dogs wag their tails.
My cat Fifi wags her tail.
My cat Fifi is a dog.

You can see that the above argument is invalid. We know that wagging the tail is not what determines what kind of animal it is. The word that makes this statement tricky is "All", because it identifies a category, a "set" as we say in logical philosophy. Just because all dogs wag tails does not make that behavior exclusive to dogs. But being a dog is the thing that determines that the animal will wag its tail. But the following argument would be valid.

All dogs wag their tails.
Max does not wag his tail.
Max is not a dog.

This is a valid logical argument.

Answer 4

God exists.