Logical Flaw Flashcards
(14 cards)
Logical Flaw: Overview
- Many Logical Flaw questions are just advanced Assumption questions.
- In answering a Logical Flaw question, our job is to do one of 2 things:
- *1) Pure Logical Flaw**: Choose an answer that best describes a flaw found in the argument
- *2) Hybrid Logical Flaw/Weaken**: Choose an answer that, if true, would weaken the flawed argument.
- Answer choices that strengthen the argument don’t point out flaws in the argument.
Logical Flaw: Question Stem
Examples:
- Which of the following best describes the error of reasoning contained in the argument above?
- Which of the following best describes a weakness present in the argument above?
Logical Flaw Question Type:
1) Pure
- Some Logical Flaw questions are pure Logical Flaw questions, meaning they ask us to point out a flaw in the argument as it currently stands and without bringing in new info in the correct answer. A flaw in the argument must always exist within the argument, and without the interjection of outside information.
- Different from Weaken the Argument: In answering a pure Logical Flaw question, we aren’t seeking to weaken the argument. Rather, our goal is to highlight an aspect of the argument that is flawed.
Logical Flaw Question Type:
2) Hybridized with Weaken the Argument
These questions ask us to point out a flaw in the author’s argument, but they bring in new info in the correct answer, in a way quite similar to the way in which regular Weaken the Argument questions do.
Logical Flaw Question Common Flaws:
1) Errors in Reasoning Involving Cause and Effect
- Reversing the relationship: A causal relationship exists but is the reverse of what is stated in the argument (X causes Y rather than Y causes X)
- Alternative cause: A correlation between two variables could be a mere coincidence, and there’s no cause-and-effect relationship between the variables.
- Third variable: A third factor causes both the given factors in the argument, but there is no cause and effect relationship between the two variables (Z causes both X and Y).
Logical Flaw Question Common Flaws:
2) Overgeneralization and Sampling Flaws
When we analyze data from a relatively small sample, we risk making incorrect conclusions.
Logical Flaw Question Common Flaws:
3) Confusion related to Numerical Info
Errors involving numbers, percentages, and other numerical info. e.g., a decline in % doesn’t necessarily mean a decline in absolute #
Logical Flaw Question Common Flaws:
4) Conclusions Unsupported by Evidence
Arguments can be flawed because their conclusions aren’t actually supported by the evidence provided.
Logical Flaw Question Common Flaws:
5) Sufficient vs. Necessary/Significant Info
When an argument that requires sufficient info for arriving at its conclusion uses necessary/significant info instead, that argument will be flawed.
Sufficient condition: If we know that an animal is a shark, then we have evidence sufficient for concluding that it is a fish. All sharks are fish.
Necessary condition: Water is necessary for the growth of plants. Without water, plants will not grow So, the presence of water is a condition necessary for the growth of plants.
HOWEVER, is the presence of water sufficient for concluding that a plant will grow? No. Plants need inputs other than water in order to grow.
Logical Flaw Questions: Incorrect Choices
1) Describes Things that the Arguments Don’t Actually Do
Some answer choices to Logical Flaw questions are blatantly incorrect because what they describe is not what the authors or arguments actually do.
Logical Flaw Questions: Incorrect Choices
2) Bring Up Things that the Argument Does but are not Flaws
In order for a Logical Flaw answer choice to be correct, it has to have 2 characteristics:
- It has to describe something that actually goes on in the argument
- What it describes has to be a flaw in the argument
Many Logical Flaw incorrect answer choices satisfy the first criterion, as they describe things that the authors or arguments actually do, but do not satisfy the second one, as what they describe are not flaws.
Logical Flaw Questions: Incorrect Choices
3) Describe Flaws in the Support for the Wrong Conclusions
A Logical Flaw question may include one or more incorrect answer choices that describe flaws in support for conclusions that are related to the conclusion of the argument but are not actually the conclusion of the argument.
Logical Flaw Questions: Incorrect Choices
4) Bring up Math Info that Doesn’t Matter
In answering Logical Flaw questions, to avoid incorrect answer choices that bring up mathematical information that seems to matter but doesn’t really matter, we must:
- be very clear about what the argument is seeking to support, and
- go beyond choosing a choice that merely “sounds right” to carefully considering the logical relationships between any mathematical information presented in answer choices and what the argument is seeking to support.
Logical Flaw Question:
Comparison is Tricky
There is a difference between being unusually large (or small) and being larger (or smaller) than something else. A rabbit is much larger than a mouse, but a rabbit isn’t an unusually large animal.
