Flaws and Assumptions

[pkalamaras]

I just noticed something today as I got a question wrong on a flaw LR question in my homework and that is that I circled the answer choice the was the assumption of the argument which is not the same as the flaw. (page 94 in LR strategy guide question on good health and educational levels - December 2002, S4, Q20). I chose A though when I looked back I could see that answer choice A was an assumption and D was the flaw. Is this correct? Is it common for the LSAT to do this sort of thing to trick you as you're altering between different question types?

[dan]

Tough question. The short answer is no. This difference between (A) and (D) is not that one is an assumption and the other a flaw.

Before we discuss it in detail, a few things to keep in mind. Flaw questions are assumption questions in disguise. When they ask you to identify a flaw, they are essentially asking you to identify an assumption. Let's take a simple example.

John was late for class.
Therefore, we know that John got stuck in traffic.

Assumption language: John was not late for any other reason aside from traffic.
Flaw language (1): Presumes that John was not late for any other reason aside from traffic.
Flaw language (2): Takes for granted that John was not late for any other reason aside from traffic.
Flaw language (3): Fails to consider that something besides traffic could have caused John to be late.
Flaw language (4): Ignores/overlooks the possibility that something besides traffic could have caused John to be late.

Notice that all of these flaws are just different ways of getting at the assumption. So, you actually DON'T want to think of assumptions as inherently different from flaws. They are basically the same thing. The issue you're having with this particular question is actually something different. Let's break it down.

The argument is this:

correlation between good health and high levels of education
thus, good health is the result of making informed lifestyle decisions

For the sake of exercise, let's change the conclusion slightly to control for a separate issue we'll discuss later. For the moment, we’ll assume that making informed lifestyle decisions and being highly educated are equivalent concepts:

correlation between good health and high levels of education
thus, good health is the result of being highly educated

This argument has a correlation vs. cause issue. Just because two things are correlated doesn't mean that one necessarily results from the other. Here's the assumption/flaw language:

Assumption: There isn't a third factor that causes both high education levels and good health (eg, socioeconomic status).
Flaw language: Ignores/overlooks the possibility that a third factor may cause both high education levels and good health.

This is exactly what answer (D) says. So, one issue is this issue of cause vs. correlation.

Let's look at a second issue. Here's the original argument:

correlation between good health and high levels of education
thus, good health is the result of informed lifestyle decisions

This time let's change it slightly to eliminate the cause/correlation problem (we've already considered that):

good health is the result of high levels of education
thus, good health is the result of informed lifestyle decisions

In this case, there's an implicit connection made between high education levels and informed lifestyle decisions. We're assuming that highly educated people make informed lifestyle decisions. This is a flaw! If this were one of the answer choices, it would be a correct flaw. Answer (A) kind of gets at this assumption/flaw, but do we need to assume that ONLY highly educated people make informed lifestyle decisions? No. Maybe other kinds of people make informed decisions as well. Who cares as long as highly educated people do.

This is why (A) is wrong... NOT because it is an assumption instead of a flaw.

Make sense?

dan

[lichenrachel]

This is of tremendous help. Thanks Dan!

[shaynfernandez]

Stuck between D and E.

Like you said the argument is causal, it has a causal conclusion. From my understanding there are a few ways to weaken, or flaws in causal reasoning.

1. Correlation not cause
2. Cause is actually effect and vice versa.
3. There is a third party causing, choice D.
4. The cause occurs effect does not
5. Effect occurs while cause does not.

I feel like E displays #5.
If informed life style choices causes good health then it always causes good health.
So if E is correct and some people don't display the presumed cause (informed lifestyle choices) but we get the effect (good health) that is a flaw.

Though E is difficult because I am not sure that "good health is largely the result if informed life style choices" is an absolute qualification for causal reasoning. But, if it is not than answer choice D wouldn't be a flaw then either.

[hdw217]

We all know to weaken a causation you do one of the following:

1. Show alternative Cause
2. Show reversal
3. Show Actually no Effect
4. Show Cause happens but no Effect
5. Show Effect happens but no Cause

The one i'm having issue is no.5, showing effect happens but no cause (for example, A causes B, and show that B happens but no A). Wouldn't one be assuming that the author is saying only A can cause B?

Thought process,

trying to weaken dude: B happens, but A did not happen, and since if A did not happen, B should not happen, A did not cause B

rebuttal by author of stimulus: but I didn't say only A can cause B

One issue I have is Preptest 39 Section 4 Question 20,

Stimulus says Informed Lifestyle Choices (ILC) Causes Good Health (GH)

1. Doesn't answer B show: ILC, but no GH (shouldn't this weaken)?

2. Doesn't answer E show: no ILC, but got GH (shouldn't this weaken)?

3. I fully understand why D is the answer but unsure of why B and E aren't correct answers.

If you could be so kind as to help me on this, would be forever grateful!!

[ManhattanPrepLSAT1]

The issue is created by the task set out by the question type. Flaw and Weaken questions don't ask for the same task.

To weaken an argument, we don't need to disprove the conclusion, we just need to add something that makes the conclusion a little less likely to be true. If I say that A causes B and you find a situation where A happened, but B did not or where B happened, and A did not, you do cast a little doubt on my assertion. Why didn't B happen when A did? How did B happen when A didn't? Could something else have caused B instead?

On Flaw questions however, we're really looking for a necessary assumption of the argument. Answer choices (B) and (E) on PT39, S4, Q20 both begin with similar language.

Overlooks the possibility that...
Does not acknowledge that...

In both cases the remainder of the answer choice would need to state that something the argument assumed to be true, was in fact not true.

Hope that helps!

[brandonhsi]

Could you explain why you stated "In both cases the remainder of the answer choice would need to state that something the argument assumed to be true, was in fact not true."?

Answer choices (B) and (E) on PT39, S4, Q20 both begin with similar language:

Overlooks the possibility that...
Does not acknowledge that...

When we see this kind of language in the flaw questions, isn't that we need to judge the answer choices WEAKEN the argument or not? If so, aren't (B) and (E) do weaken the argument?

Thanks!

[ohthatpatrick]

You're right to think that "overlooks/ignores/neglects to consider the possibility" answers would Weaken, but it would Weaken like a negated assumption would weaken (that is, REALLY cripple the argument, not just introduce a little doubt).

That's what Matt meant about the "rest of the answer" ... it should read like a negated necessary assumption.

(B) and (E) do not really Weaken the argument because the conclusion's language is safely qualified by saying, "good health is largely the result of making informed lifestyle choices."

That conclusion leaves plenty of room for shades of gray ... i.e. exceptions to the general rule.

So the author's conclusion freely allows for, if not acknowledges, what (E) is saying ... that SOMETIMES good health comes to those who haven't made informed lifestyle choices.

(B) doesn't weaken the author's position, because the author never implied that informed lifestyle choices would guarantee good health. He's not guaranteeing anything, but he's suggesting that if you have good health you probably made informed lifestyle choices. Be careful when the strength of language leaves room for exceptions ... if the author is saying that A is generally accompanied/caused by B, it doesn't weaken the author's case to say that sometimes A occurs without B or sometimes B occurs without A.

Hope this helps.

[brandonhsi]

Thanks! You help me understand the question better.

I was wondering why you prefer to use the word "weaken" here (flaw question), when you really mean "destroy"? Before this, I thought "weaken" only means you could weaken the argument a little bit, a lot, or destroy the argument.

Also, if this question is asking for something "weaken" the argument (like in a weaken question, NOT a flaw question), both (B) and (E) would be correct, since they do "weaken" the argument at least a little bit?

Thanks again!

[ohthatpatrick]

We never really use the word 'destroy' in talking LSAT, so I was sticking with our common term Weaken.

You're correct that on a Weaken question, the correct answer could potentially be anywhere on the continuum from "barely weakens to totally destroys".

There are many different flavors of Weakening, but generally correct Weaken ideas pack a pretty good punch. It's rare, though acceptable, for our one correct answer on a Weaken question to barely Weaken.

If I'm thinking in terms of "Does this assumption, when negated, Weaken?", then I'm only thinking in terms of "does this pack a pretty good punch".

I do not think that (B) or (E) weaken this argument, for the reasons I said before. The author's conclusion leaves plenty of room for exceptions, and all (B) and (E) try to do is point out that some exceptions might exist. I don't see how you can call that Weakening.

Beware of adhering to a rigid list like that proposed earlier in the thread.

Cause w/o effect does not HAVE to weaken.

If my conclusion is that "sneezing normally causes people's eyes to close" and (B) says "some people are open-eyed sneezers", that is cause w/o effect but it does not weaken.

It's helpful to know patterns of correct answers such as "cause w/o effect" / "effect w/o cause", but they aren't enough on their own. You have to consider the strength of language of the argument's conclusion as well as the strength of language of the answer choice.

For instance, if (B) said "most people are open-eyed sneezers", then that DOES weaken.

An answer choice that points out that SOME exceptions may exist is only an objection if the author was assuming that NO exceptions exist.

Hope this helps.