Logically weakening something

[ericha3535]

Ok... I have a question about weakening type question in general.

Let's say argument says something like:
A was there.
B was there
BUT!
A is the cause, not B.

And the question stem asks us to weaken the argument,

Will answer choice that introduces another possibility will weaken the argument?

For example, answer choice that says: No, C is the cause.

[tommywallach]

Hey Ericha,

I'm wary of really vague hypothetical conversations like this. ANYTHING that weakens the relationship between the premise and the conclusion is a legitimate weakener. So in your vague example, it would depend:

If the conclusion is that A caused something, you could weaken that by providing evidence that B caused the thing.

If the conclusion is that A did not cause something, you would be strengthening the argument by providing evidence that B caused the thing.

You can't do both at once, for obvious reasons.

Hope that helps!

-t

[ericha3535]

Thanks for the reply Tommy.

Then please allow me to give you a specific example.

There was a candy on Jessica's table. As leaving to work, she saw the candy. It was 9am. When she came back home from work at 9pm, the candy was gone.
It was hypothesized that Martha, her only roommate, was the one who ate the candy since she likes to eat candy all the time.
However, Martha did not eat candy for sure because she was too ill to eat anything.
Therefore, it was Jessica's dog, rather than Martha, that ate the candy.

Now, if the question stem says: which of the following would weaken the argument and the question choice says:

A: Martha has a cat named John and John would eat anything that is sweet.

Would A weaken the argument?

Of course I am not an expert and probably this is a horrible argument and an answer choice but you see what I am trying to do right?

Argument: The cause of appearance of candy is Jessica's Dog not Martha.

Answer choice: Actually, Martha's cat could have been the culprit.

To me, such answer choice (alternative factor) would weaken the argument.

I hope I am making sense...

[tommywallach]

Hey Ericha,

That was a great argument! And yes, that would totally weaken the argument. And probably end up killing that cat.

: )

-t

[ericha3535]

Dear Timmy,

Thank you for your response.

I think... I did not make the argument as I intended.

umm... here is the revised one.

There was a candy on Jessica's table. As leaving to work, she saw the candy. It was 9am. When she came back home from work at 9pm, the candy was gone.
It was hypothesized that Martha, her only roommate, was the one who ate the candy since she likes to eat candy all the time.
However, Martha was ill that day so she had less appetite compared to other days.
Therefore, it was Jessica's dog, rather than Martha, that ate the candy.

Now, if the question stem says: which of the following would weaken the argument and the question choice says:

A: Martha has a cat named John and John would eat anything that is sweet.

Would A weaken the argument?

Note: so what I was getting at was that... in that argument, we can't really exclude Martha as the one that did not really eat the candy, since having less appetite does not preclude the chance that she ACTUALLY DID'T eat the candy.

So... in that case, is introducing new alternative (other than a choice that would say something about Jessica's dog or Martha) going to weaken the argument?

Sorry for dragging this... just wanted to know for sure!

Thanks

[tommywallach]

Hey Ericha,

Well you've asked the wrong question. Yes, that still weakens. But the LSAT would never do that, because the premise is about illness. They wouldn't just psych you out like that (illness had nothing to do with this!). And that's all I'll say about that!

-t