If unstated assumptions are the glue that holds an argument together, then weakening or strengthening the assumptions will weaken or strengthen the argument. Nearly all Strengthen/Weaken questions don't ask you to change the conclusion or the premises, because those are fixed; it is the unstated assumptions that are in flux. The whole trick on the Strengthen/Weaken question is to strengthen or weaken the assumptions.
Strengthening and Weakening are not the same thing as proving something true or false. Instead, the right answer will support (strengthen) or cast doubt upon (weaken) the required assumptions, while also being relevant to the premises.
Here are some examples of Strengthen/Weaken question stems:
Strengthening:
- The conclusion would be more properly drawn if it were made clear that...
- Which of the following, if true, would most strengthen the conclusion drawn in the passage above?
- The argument as it is presented in the passage above would be most strengthened if which of the following were true?
Weakening: (note that when it says "if true", means that you must accept the validity of the statement)
- Which of the following, if true, most seriously weakens the conclusion drawn above?
- Which of the following, if true, would provide the strongest evidence against the above?
- Which of the following, if true, casts the most serious doubt on the conclusion drawn above?
Tips for Weakening Questions:
- Try to find one necessary assumption in the passage. This is what the right weakening answer will often target.
- The All Things are Equal fallacy is very common on these questions. When things are compared over time, the assumption is that background factors remain constant (while they might be changing). A good answer might point out that some background factor did change.
- When you see a Weakening question that compares two things or tries to show them as similar, look for an underlying factor that makes such a comparison problematic.
- There will likely be two or more choices that weaken the argument. In this case, re-read the passage carefully and see which one is most directly relevant to the premises, the conclusion and assumptions.
- Common trap answer choices include:
- A statement that strengthens (and doesn't weaken) the assumptions and the overall argument- a trick opposite.
- A statement with information not relevant to the argument.
- A statement that requires additional facts to have value.
- The final answer that remains is the correct answer.
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Use strong language to weaken or strengthen
On most other Verbal questions, you can eliminate potential answers that use strong language. The exception is the Strengthen/Weaken questions. On these questions, sweeping words are more effective:
only
the most
extremely
all
The reason? Extreme answers will have a more powerful weakening/strengthening effect on assumptions. |
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Sample Questions
We've disuccsed this example several times. Use the information gained above to generate an answer based on targeting assumptions:
- The postal service is badly mismanaged. Thirty years ago, first-class letter delivery cost only three cents. Since then, the price has increased sevenfold, with an actual decrease in the speed and reliability of service.
All of the following would tend to weaken the conclusion of the argument above EXCEPT:
- The volume of mail handled by the postal service has increased dramatically over the last thirty years.
- Unprecedented increases in the cost of fuel for trucks and planes have put severe upward pressures on postal delivery costs.
- Private delivery services usually charge more than does the postal service for comparable delivery services.
- The average delivery time for a first-class letter three decades ago was slightly longer than it is today.
- The average level of consumer prices overall has increased fourfold over the last thirty years.
Explanation:
The conclusion is that the postal service is poorly managed. This is an EXCEPT stem, so we are looking for something that won't weaken the argument. |
| Premise #1 |
the price of first-class delivery has increased sevenfold |
| Premise #2 |
there has been a decrease in speed and service. |
| Conclusion |
The postal service is badly mismanaged |
| Analysis |
This is the All Things are Equal fallacy. It assumes conditions don't change, thereby making a basis of comparison over time. This compares past performance to the present day. So, of course anything that suggests that business conditions have gotten harder will excuse managerial incompetence. Anything that suggests conditions have gotten easier will not weaken the argument, so that's what we are looking for. |
Reviewing Answer Choices
- The volume of mail handled by the postal service has increased dramatically over the last thirty years.
This would seem to excuse the poor service/price because the service has had to overcome a massive increase in volume.
- Unprecedented increases in the cost of fuel for trucks and planes have put severe upward pressures on postal delivery costs.
This would seem to excuse the poor service/price because costs have increased dramatically.
- Private delivery services usually charge more than does the postal service for comparable delivery services.
This would seem to excuse the poor service/price because other services are not as efficient.
- The average delivery time for a first-class letter three decades ago was actually slightly longer than it is today.
This shows they have made improvements in service, suggesting that the postal service isn't all that bad after all.
- The average level of consumer prices overall has increased fourfold over the last thirty years.
Since the price of postage has increased seven times over, this suggests that postal prices have increased at a rate much quicker than inflation. Thus, choice E does support the original argument, making this the correct answer.
- In many pre-schools, children tend to commonly get colds before their resistance develops and the colds become much less frequent. It is clear that a child requires several colds before white blood cell concentrations rise high enough to effectively deal with colds.
Which of the following, if true, most seriously weakens this theory?
- Children commonly spread viruses and bacteria in a small closed environment.
- The use of Vitamin C increases resistance to the common cold and decreases its frequency.
- Parents stock up on cold medicine after a child gets sick that alleviate the symptoms of a cold.
- There are many strains of the cold virus and children develop resistance to individual strains.
- White blood cells fight infection and their production levels are stimulated by high infection levels.
Explanation:
The question is stating that the body's immune system requires numerous infections to be properly stimulated. It is a causal argument that tries to explain an observation. |
| Premise #1 |
Children tend to get fewer colds as they progress through pre-school. |
| Premise #2 |
(unstated assumption) |
| Conclusion |
It takes several colds to activate a child's immune system. |
| Analysis |
This is After This, Therefore, Because of This fallacy. It observes that as children go through pre-school the number of colds go downs. From this, the creative author develops the theory that a child's immune system requires them to get several colds before it is fully activated.
The best way to weaken a causal argument is to suggest an alternative causal factor (find a confounding issue). |
Reviewing Answer Choices
- Children commonly spread viruses and bacteria in a small closed environment.
Not Relevant
- The use of Vitamin C increases resistance to the common cold and decreases its frequency.
Not Relevant
- Parents stock up on cold medicine after a child gets sick that alleviate the symptoms of a cold.
This choice presents another possible reason to undermine the argument, but the medicine deals with symptoms, not the cold per se. So it is not reducing an instance of a cold, simply decreasing their symptoms (no more runny noses!).
- There are many strains of the cold virus and children develop resistance to individual strains.
This choice suggests an alternative explanation for the apparent improvement in a child's ability to fight colds: the child simply becomes immune to individual viruses per se. So, the theory that a child's immune system needs high white blood cell concentrations isn't the case, it is an issue of exposure to certain strains. By suggesting a different causal process to explain the reduction in colds, it weakens the argument.
- White blood cells fight infection and their production levels are stimulated by high infection levels.
This choice supports this statement, but the question asks for what weakens it.
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Trick Opposites
Trick opposites are sometimes used as junk answer choices on Strengthen/Weaken questions. If the stem asks for what weakens the passage, you'll find a perfect answer choice for what strengthens it, and vice versa.
Choice (E) in the above question about colds is an example of a trick opposite. |
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