Q from BJU Geometry Ch 5 p 204 - why is this valid/false

[74Heaven]

I can't figure this out: (the answer key says this is Valid/False

 

Premise 1 Joe has a pet boa constrictor named Hugger.

Premise 2 No snakes are pets.

Conclusion Therefore, Hugger is not a snake.

 

To me, premise 1 is true/valid

Premise 2 is not true/invalid/logical?

Conclusion is false

 

So the problems is invalid/false.

 

Definition (p 183): An argument is Valid if the reasoning proceeds logically from the premises to the conclusion.

 

The book (p 184) says: I the study of reasonin you must be a ware that validity and truth are very different things. An argument that is valid can result in a false conclusion.

 

The book goes on to say: an argument that is invalid can result in a true conclusion. Yu must be able to distinguish valid arguments from true conclusion. If a conclusion of an argumnt is false, but the reasoning is valid, then the argument is not sound and you automatically know that at least one of the premises is false.

 

(OK, I think I understand - why is the above argument Valid? HOw is the "resaoning" valid????) Is the answer key wrong?) I hope I didn't confuse things further?

 

Lisaj, mom to 5

[JenneinCA]

I think I understand what you are trying to figure out.

 

Given Premise 1 and Premise 2 then the Conclusion is consistent. That would mean the problem is "valid". IF both the premises were TRUE then the correct conclusion was reached.

 

But Premise 2 is not true and so the Conclusion is false.

 

And that is why they got, valid/false.

 

(If the conclusion had been "Hugger is a snake" then the Conclusion would have been invalid because that doesn't follow from the premises.)

[74Heaven]

I think I understand what you are trying to figure out.

 

Given Premise 1 and Premise 2 then the Conclusion is consistent. That would mean the problem is "valid". IF both the premises were TRUE then the correct conclusion was reached.

 

Ok, I don't understnad how Premise 1 & Premise 2 make the Conclusion "consistent".

 

To me Premise 1 is a given, thus "valid" but premise 2 is *not* true/valid since we all know some people have pets for snakes.

 

so how does the conclusion "follow" from two distinctly opposite premises (i.e. Premise 1 says a snake (boa constrictor) *is a pet* and Premise 2 says "snakes are *not pets*"?

 

still confused - and I apologize for all the typos in the first post - in a hurry

Lisaj

[JenneinCA]

You have to assume that Premise 1 and Premise 2 are true to test for consistency (validity).

 

Try this:

 

Premise 1: Felix is a alien.

Premise 2: All aliens are yellow.

 

Conclusion: Felix is yellow.

 

When testing for validity, you only check to see if the conclusion follows directly from the premises. Do not worry about whether the premises themselves are true. You deal with that later when you check for TRUE/FALSE.

 

So this is valid. It may or may not be true. We don't know anything about the colors of aliens.