3026 Recovery speeds of patients

[vincent.m]

Hi again guys,

I feel like the correct answer is a sufficient assumption while the incorrect answer could be a necessary assumption or am I overthinking it? Can someone please shed some light on this? Thank you!

[ohthatpatrick]

Hey, Vincent.

I don't have access to that question (I'm awaiting an email back from someone who does), but if you can find it and just copy / paste into this thread, then I can answer your question sooner.

Thanks.

[vincent.m]

Sorry it took me so long to respond!

P: Patients with disease E who demonstrated increased levels of optimism have shown increased recovery speeds.

(A): (No factor other than the level of optimism can be responsible for any change in recovery speed in patients with disease E.)

(A): (Recovery speed does not cause the level of optimism to increase in a patient with disease E.)

C: Increased levels of optimism of a patient with disease E are responsible for increasing recovery speed.

[ohthatpatrick]

You're definitely correctly sensing that A1 has the feel of Sufficient Assumption while A2 has the feel of Necessary Assumption.

The premise we have is:
Ppl who have trait X also have trait Y

Authors will almost always conclude from that
"X causes Y" or "X is the explanation for Y"

However, in order to draw that sort of conclusion from a correlation between X and Y, you have to rule out all other possible explanations.

What LSAT will want you to consider each time is:
"Hmm, is it possible that Y actually caused X?"
and
"Hmm, is it possible that something else, Z, caused Y?"

A quick example:
People who nap a lot have frequent bouts of insomnia.
Therefore napping causes insomnia.

We think:
"Hmm, is it possible that having insomnia caused the napping?"
and
"Hmm, is it possible that something else, like a genetic defect, causes the napping and the insomnia?"

So A1 in this question essentially said:
"Nothing other than X can cause Y"

and A2 said
"Y didn't cause X"

A2 isn't going to PROVE to us that X caused Y, because all it does it rule out ONE possible alternative interpretation of the correlation. It still leaves open the possibility that some other factor, Z, caused Y.

But, as you realized, A2 would be a Necessary Assumption, because if we negate it, it severely weakens the argument.

If we negate A2, we get "Y did cause X".

That's a killer counter-punch to someone who looks at a correlation between X and Y and infers "X caused Y".

Meanwhile, A1 is sufficient because of how sweeping it is. NOTHING other than X can cause Y to happen.

Well, do we know that Y happened?

Yes, the premise said that people DID have increased recovery speeds.

Well A1 tells us that the only possible explanation for that is Level of Optimism.

That allows us to conclude that the increased recovery speeds were due to the change in level of optimism.

===== technicality ------
Technically the conclusion isn't 100% proven.

If I say
1. Y happened.
2. Nothing other than X can cause Y to happen.

can we conclude
X caused Y to happen?

As far as common sense is concerned, yes, but for the sake of formal logic you'd really have to also assume
"Y was caused"
or, in other words,
"SOMETHING must be responsible for Y."
============

Hope that helps.