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Course: LSAT > Unit 1
Lesson 6: Logical Reasoning – Articles- Getting started with Logical Reasoning
- Introduction to arguments
- Catalog of question types
- Types of conclusions
- Types of evidence
- Types of flaws
- Identify the conclusion | Quick guide
- Identify the conclusion | Learn more
- Identify the conclusion | Examples
- Identify an entailment | Quick guide
- Identify an entailment | Learn more
- Strongly supported inferences | Quick guide
- Strongly supported inferences | Learn more
- Disputes | Quick guide
- Disputes | Learn more
- Identify the technique | Quick guide
- Identify the technique | Learn more
- Identify the role | Quick guide
- Identify the role | learn more
- Identify the principle | Quick guide
- Identify the principle | Learn more
- Match structure | Quick guide
- Match structure | Learn more
- Match principles | Quick guide
- Match principles | Learn more
- Identify a flaw | Quick guide
- Identify a flaw | Learn more
- Match a flaw | Quick guide
- Match a flaw | Learn more
- Necessary assumptions | Quick guide
- Necessary assumptions | Learn more
- Sufficient assumptions | Quick guide
- Sufficient assumptions | Learn more
- Strengthen and weaken | Quick guide
- Strengthen and weaken | Learn more
- Helpful to know | Quick guide
- Helpful to know | learn more
- Explain or resolve | Quick guide
- Explain or resolve | Learn more
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Types of flaws
Common Flaws
On the LSAT (as well as in real life), you’ll encounter some types of flawed arguments more often than others. This article features some of the flaws that you’re most likely to see on Test Day. This article is in no way comprehensive, but rather a good start in introducing some typical flaws.
The faster you can recognize these common flaws, the more time you'll be able to save if you encounter them on Test Day
Where am I most likely to use my knowledge of common flaws?
You'll often encounter classic flaws in the arguments and choices in these Logical Reasoning question types:
- Identify a flaw
- Match flaws
And, knowledge about these flaws can sometimes help you identify potential weak points in these question types:
Top tip: Flaws don't fit into one neat, predetermined box. There are many ways to name the same flaw. It simply depends on how you look at the situation. For example:
Lachelle is late for dinner, so she must be stuck in traffic.
It's equally accurate to state the flaw as:
- The arguer assumes without warrant that traffic is the only reason Lachelle would be late for dinner
or
- The arguer overlooks the possibility that traffic is not the only reason Lachelle would be late for dinner.
Don't worry, though! As long as you practice and recognize the conceptual flaw in an argument, you'll soon get better at recognizing the different ways that flaws can be described in the choices.
Let's take a look at some classic flaw varieties so that you can recognize and approach them with more confidence on Test Day.
Sampling
Sampling flaws occur when an argument extends limited information and tries to apply it more widely than is reasonable or justifiable.
To detect a potential sampling flaw, look for:
- Polls, surveys, or studies
- Data or statistics that come from a limited source (such as "one meteorologist")
- A shift from specific evidence to a general conclusion (for example, the evidence is about three doctors and the conclusion is about all doctors)
- A shift from evidence to conclusion during which the arguer assumes—but doesn't demonstrate—that one is acceptably representative of the other
To confirm that a sample is representative, we're primarily concerned about making sure the sample addresses:
As you work through the next exercise on your own, look for how the sampling flaw appears and how you can detect it on your own.
Ad hominem
You can most easily observe an ad hominem flaw when:
- An arguer criticizes someone's actions as a reason to not heed their argument
- An arguer criticizes someone's character as a reason to not heed their argument
- An arguer criticizes someone's motives as a reason to not heed their argument
It's important to remember that the identity or motives of an arguer don't affect the validity of that person's argument. Corrupt, unintelligent, biased people can make valid arguments. Moreover, if someone’s a hypocrite (they act in a different way than what they advise), it doesn’t mean they’re wrong.
Example: My doctor tells me it's bad for your lungs to smoke cigarettes, but I know he's lying. I saw him furtively smoking a cigarette the other day.
Our next example question should challenge you a bit, since it'll show you several types of ad hominem flaws in the choices. Be precise! Not all ad hominem flaws are created equal.
Faulty analogy
A faulty analogy is a type of Scope Shift, in that the arguer compares two things or two situations, but the two things or situations being compared aren't sufficiently alike.
If you detect an analogy in an Assumption or Strengthen/Weaken question, you may need to demonstrate that the two things or situations in the analogy are (or aren't, as in the case of Weaken questions) sufficiently alike.
Summary of common flaws
This table includes the flaw types we discussed above, as well as a few others that are less common. Feel free to bookmark this article in your browser so that you can review it from time to time! This list is not meant to be comprehensive, but rather a great starting point for you to understand a good portion of LSAT flaws.
Top tip: Make your own! Try to create your own examples to illustrate each flaw. It's a great exercise to demonstrate your understanding!
Flaw | Explanation |
---|---|
Causation/correlation | This is an important type of overlooked possibility, in which the arguer takes two things that happen at the same time (correlation) and concludes that one of those things caused the other (causation). The arguer overlooks two important possibilities: 1) a third, unaccounted-for thing could actually be the cause, and 2) the cause-and-effect could actually be in the reverse order of what the arguer believes. Example: Last summer, ice cream sales decreased while homicide rates more than doubled in this region. We should look into selling more ice cream in order to keep people safer. |
Sampling | The arguer draws a general conclusion based on what's true about an inappropriate or biased sample. Example: Everyone I know wants to quit their job, so this country is headed for an employment crisis. |
Ad hominem | The arguer attacks another arguer instead of the argument itself. The identity or motives of an arguer don't affect the validity of that person's argument. Example: My doctor tells me it's bad for your lungs to smoke cigarettes, but I know he's lying. I saw him furtively smoking a cigarette the other day. |
Quantity versus percent | The arguer treats quantities and percents of something as if they're interchangeable, but percents by themselves don't tell you anything about actual numbers. Example: 10% of the people with Disease X died last year, whereas 50% of the people with Disease Y died last year. Clearly, Disease Y is hurting our population growth more than Disease X is. (But what if 1,000,000 people had Disease X and only 4 people had Disease Y?) |
Lack of evidence as proof | The arguer takes a lack of evidence for a conclusion as if that conclusion is definitely wrong. Also known as taking an absence of evidence for "evidence of absence". Example: Alien life has never been discovered, so it's clear that alien life doesn't exist. |
False dichotomy | The arguer acts like there are only two choices, when in fact it isn't an "either/or" situation. Example: If you're not with us, then you're against us. The arguer is overlooking the possibility that someone could remain neutral. |
Possible vs. certain | The speaker assumes that because something is possible, then it'll happen. Example: Last year we didn't have enough budget money for employee raises, but this year there's plenty of money in the budget. So, it's clear that the company will give out raises this year. |
Circular reasoning | Also known as "begging the question", circular reasoning is when the arguer assumes that his or her conclusion is already true when attempting to prove that same conclusion. Example: Duplicity is an unattractive characteristic, since it's repulsive to lie and deceive. |
Equivocation | The arguer uses a potentially ambiguous term in more than one sense and consequently misleads the reader. Example: A feather is light, and what's light can't be dark, so a feather can't be dark. |
Your turn
Using what you've learned in this article, try a mixed group of practice questions. Break the arguments into conclusion and evidence, and look for clues that may signal one of the classic flaws we covered.
Want to join the conversation?
- Hi there,
In the second example question in Mullen's proposal. We go with answer B.
What about thinking it like this; Answer A is right because he is effected in the outcome of his own policy (negative or positive - he is just effected) and we don't need to assume anything.
To make answer B right we have to assume something! Isn't it a stretch to assume that the Dr would lose if the proposal becomes a reality? Just because he is a heavy smoker why does that tell us he will lose by this policy? (we don't know he smokes in public places) Maybe he didn't smoke in public places before the policy became effective and wont be affected by the policy at all. Why assume something if we can answer the question by going with the facts given.
Mullen's proposal if you had a capital gain = (he had) will be effected.
Smith's proposal - working parent (he is) will be effected.
Dr Han's Ban on smoking in public places = (Does he?) Heavy smoker doesn't necessarily tells us about where he smokes.
The flawed reasoning is more similar to A if we look at the fact that he gets effected in the policy he is proposing albeit not in the same way one is negative and one is positive ....but the flaw in reasoning still matches. VS. answer B we need to bring in an assumption to include Dr in his own policy, something we didn't need to do for Mullen, the reasoning itself changes.(7 votes)- I might be able to help. I will first summarize what you are saying in one sentence.
"Mullen and Smith are the ones that will be affected by their own proposals; however, we don't know if Dr. Han will be affected by his own proposal and 'assuming' that he will be is a stretch."
In short, I think you are simply over-thinking. It is true that we don't know a thing about Mr. Han other than he's a heavy smoker, but then, do we know anything about Smith? How can you be certain that Smith will be affected by what he proposes? He might not have any kids yet or he might not have been married yet! With your logic, wouldn't it be a stretch to say that Mr. Smith is the one who will be affected?
Critical thinking and being doubtful are good qualities to have when taking the LSAT, but it is also essential to accept what the passage and answer choices tell you. Especially, rarely do LSAT makers want you to doubt the validity of the answer choices.
In this question, answer choices A, B, and D all talk about a person's proposal affecting him/herself. A person's proposal negatively affects him/her only in answer choice B as in the passage and thus, B is the answer.
Hope this helps.(14 votes)
- The "Circular Reasoning" or "Begging Question" is still not very clear to me. Can someone help me with this by giving me a real test question? Thanks!(9 votes)
- Restates the premise in the conclusion(3 votes)
- You'll often encounter classic flaws in the arguments and choices in these Logical Reasoning question types:
Identify a flaw
Match flaws
Here What is meant by "classic Flaws"? Flaws and classic flaws are different because the flaw definition is well explained above.(1 vote) - I was also split between A and B on the Mullen question. I ended up going with B because:
Mullen: performed an action (investing)
Smith: is just Smith with a Kid (no actions)
Han: performs an action (smoking)
The argument was attacking Mullen on the basis of his actions, not the basis of his being. To me, Smith was being attacked because of who he was, not something that he does.
I didn't notice the positive/negative relationship, either. I guess I just got lucky there.(1 vote)