3.18 - Weaken

This lesson's all about Weaken questions. On Weakeners, you attack the argument (instead of defending / improving it like you do on Strengtheners).

They tend to look something like this:

• Which one of the following, if true, most undermines the mayor's claim?
• Which one of the following, if true, most seriously weakens the argument?
• Each of the following, if true, weakens the claim above except?

Like Strengtheners, these questions can be pretty challenging. The correct answer will either make the argument less likely to be true, or will simply fail to strengthen it. Wrong answers do the opposite—they'll either outright strengthen the conclusion or be irrelevant.

Let's try some practice problems.

Examples

June 2007 PrepTest, Section 2, Question 5

First up is Question 5 from Test J, Section 2:

Scientist: Earth's average annual temperature has increased by about 0.5 degrees Celsius over the last century. This warming is primarily the result of the buildup of minor gases in the atmosphere, blocking the outward flow of heat from the planet.

This is a pretty simple argument. Earth's temp has gone up over the last century. The author concludes that the temperature rise is due to minor gas buildup in the atmosphere. Why? Because the buildup blocks outward heat flow.

My prediction is that the correct answer will have something to do with this argument's evidence. That is, if we're offered an answer choice that gives a better reason why the temp's increasing, that's probably a good pick.

Let's go answer by answer.

Answer choice A sucks. Who cares if only some of the minor gases came from industrial pollution? Our author didn't discuss what caused the buildup. They only allege that it's the cause for the warming.

B piques my interest. If most of the warming occurred before 1940, but most of the gas buildup happened after 1940, there's a better chance than before that some alternative cause led to the overall increase in temp. Let's kill C through E.

C's largely irrelevant. Even if Earth received slightly more radiation in some years, (1) it might have received less radiation in other year and (2) this could even strengthen the argument that the extra radiation is trapped by the gas buildup.

D's also out of scope. Who cares about volcanic dust? We're talking about reasons for warming. This would be a possible reason for cooling.

E's actually a strengthener. If we have more gases now than ever before, then it points to the gases being a cause for warming.

Gotta pick B.

June 2007 PrepTest, Section 2, Question 9

Let's try another, this time Question 9 also from Test J, Section 2:

Although video game sales have increased steadily over the past 3 years, we can expect a reversal of this trend in the very near future. Historically, over three quarters of video games sold have been purchased by people from 13 to 16 years of age, and the number of people in this age group is expected to decline steadily over the next 10 years.

Conclusion: We can expect video game sales to reverse their steadily increasing trend in the very near future. Their evidence? 13- to 16-year olds account for a large proportion of sales, and the overall number of people in that age group is expected to drop over the next decade.

What a derpy argument. I loved video games at 8, 10, 16, 32, and everywhere in between. This argument necessarily assumes we grow out of our video game purchasing habits. What if, instead, as we grow up and gain more purchasing power, we actually buy more video games? Feels like a solid objection.

Let's go answer by answer again.

A's a strengthener. If most people over 17 have never bought a game, then maybe we do grow out of our game-buying habits.

B's irrelevant. When did we talk about rentals? Remember: Didn't read? Don't pick!

C's also a strengthener. New entertainment options increases the likelihood that game sales will drop, even if only a little.

D's also irrelevant. We're focused on the relationship between buyer age and video game sales across all types of video games.

E's our answer. If a majority of folks buying games over the past three years are 16+, then we need to account for that group's purchasing habits when we predict future sales.

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That does it for Weaken questions. Next, we tip-toe the middle ground between Strengtheners and Weakeners with Evaluate questions. See you there.