LSAT Flaw Questions Common Errors of Reasoning

Authors misusing information to such a degree that they fail to provide any information to support their conclusion or they provide information that is irrelevant to their conclusion.

“The author cites irrelevant data.”

“draws a conclusion that is not warranted by the evidence provided.”

“It uses inapplicable information to draw a conclusion about the character of the witness."

“It fails to give any reason for the judgment it reaches.”

Error in the Use of Evidence: General Lack of Relevant Evidence for the Conclusion

Occurs when an author makes conflicting statements.

“bases a conclusion on claims that are inconsistent with each other”

“the author makes irreconcilable presuppositions”

“introduces information that actually contradicts the conclusion”

“claims presented in support of the conclusion conflict with the other evidence provided.”

Error in the Use of Evidence: Internal Contradiction

Takes a small number of instances and treats those instances as if they support a broad, sweeping conclusion.

“supports a general claim on the basis of a single example”

“generalizes on the basis of what could be exceptional cases.”

“bases a broad claim on a few exceptional instances”

Error in the Use of Evidence: Exceptional Case/Overgeneralization

“treats failure to prove a claim as constituting denial of that claim”

“taking a lack of evidence for a claim as evidence undermining the claim”.

Error in the Use of Evidence: Errors in Assessing the Force of Evidence

1. Lack of evidence proving a position is taken to prove that position is false.

“treating the failure to prove a claim to be false as if it is a demonstration of the truth of that claim”

Error in the Use of Evidence: Error in Assessing the Force of Evidence

2. Lack of evidence against a position is taken to prove that position is true.

“it confuses weakening an argument in support of a given conclusion with proving the conclusion itself to be false:

Error in the Use of Evidence: Error in Assessing the Force of Evidence

3. Some evidence against a position is taken to prove that the position is false

“The argument treats evidence showing mere plausibility as if it proves that the conclusion is in fact true”

Error in the Use of Evidence: Error in Assessing the Force of Evidence

4. Some evidence for a position is taken to prove that position is true.

Attacks the person (or source) instead of the argument they advance.

“It is directed against the proponent of a claim rather than against the claim itself”

“The attack is directed against the person making the argument rather than directing it against the argument itself”

“It draws conclusions about the validity of a position from evidence about the position’s source”

“assuming that legislation should not be supported based on the character of some supporters of the legislation.”

Ad hominem

The author assumes as true what is supposed to be proved.

“argues circularly by assuming the conclusion is true in stating the premises”

“presupposes what it sets out to prove”

“it assumes what it is attempting to demonstrate”

Circular Reasoning

“taking the absence of an occurrence as evidence that a necessary condition for that occurrence also did not take place” (Mistaken Negation)

“mistakes being sufficient to achieve a particular outcome for being required to achieve it” (Mistaken Reversal)

Errors of Conditional Reasoning

“From the assertion that something is necessary to a given goal, the argument concludes that that thing is sufficient for its achievement.”

“It acts as if something that is necessary for a good leader is something that is sufficient to create a good leader.”

Errors of Conditional Reasoning (Confusing a necessary condition for a sufficient condition)

“confuses a sufficient condition with a required condition.”

Errors of Conditional Reasoning (Confusing a sufficient condition for a necessary condition)

“mistakes the occurrence of one event after another for proof that the second event is the result of the first.”

“mistakes a temporal relationship for a causal relationship.”

“confusing the coincidence of the two events with a causal relation between the two”

“assumes a causal relationship where only a correlation has been indicated”

“fails to exclude an alternative explanation for the observed effect”

“the author mistakes an effect for a cause”

Mistaken Cause and Effect

When an author attempts to attack an opponent’s position by ignoring the actual statements made by the opposing speaker and instead distorts and refashions the argument. Often this error is accompanied by the phrase “what you’re saying is” or “If I understand you correctly".

“refutes a distorted version of an opposing position.”

“misdescribing the opposing position, thus making it easier to challenge.”

“portrays opponents’ views as more extreme than they really are.”

“distorts the proposal advocated by opponents.”

Straw Man

Uses the opinion of an authority in an attempt to persuade the reader. The flaw in this reasoning is that the authority may not have relevant knowledge or all the information regarding a situation.

“the judgment of experts is applied to a matter in which their expertise is not relevant.”

“the argument improperly appeals to the authority of the supervisor.”

“bases a conclusion solely on the authority of the claimant".”

Appeal Fallacy (Appeal to Authority)

This error states that a position is true because the majority believes it to be true. Arguments are created by providing premises that support a conclusion. Examples include (“C’mon, try this; everyone does it.”) or (“Everyone loves the environment. Therefore, you should vote for the Green Party.”)

“popular sentiment is treated as definitive proof of a claim.”

“the argument tries to undermine the claim by appealing to public opinion.

“a conclusion is judged to be false simply because most people believe it to be false.”

“the author makes an appeal to public opinion without requiring an adequate basis for the conclusion of the argument.”

Appeal Fallacy (Appeal to Popular Opinion/Appeal to Numbers)

When emotionally charged language is used to persuade a reader.

“attempts to persuade by making an emotional appeal”

“the argument appeals to emotion rather than reason”

Appeal Fallacy (Appeal to Emotion)

Misconstrued surveys may be through a biased sample, confusing or misleading questions, or respondents not giving accurate responses.

“uses evidence drawn from a sample that may not be representative”

“bases a conclusion on survey responses that were gained through faulty questioning.”

“generalizes from an unrepresentative sample.”

“assumes that every polled individual provided a truthful response.”

Survey Errors

Occurs when the author attributes a characteristic of part of the group to the group as a whole or to each member of the group.

“assuming that because something is true of each of the parts of a whole it is true of the whole itself”

“improperly infers that all union members have a certain attribute from the premise that most union members have that attribute.”

“take the beliefs of one scientist to represent the belief of all scientists.”

Error of Composition

Occurs when the author attributes a characteristic of the whole (or each member of the whole) to a part of the group.

“presumes without warrant that what is true of a whole must also be true of each of its parts”

Error of Division

When the author uses the same word or concept, but they have two different meanings, with the author thinking they mean the same.

“depending on the ambiguous use of a key term”

“it confuses two different meanings of the word ‘genius’”

“the author’s conclusion depends on defining a key term in two different ways”

“equivocates with respect to a central concept”

Uncertain Use of a Term or Concept

When the author uses an analogy that is too dissimilar to the original situation to be applicable.

“treats two very different cases as if they are similar.”

“treats two things that differ in critical respects as if they do not differ.”

False Analogy

Assumes that only two courses of action are available when there may be others.

“fails to consider that some voters may be neither strong supporters nor strong opponents of the suggested amendment.”

False Dilemma

Assuming that conditions will remain constant over time, and that what was the case in the past will be the case in the present or future,

“treats a claim about the current state of affairs as if it were a claim about what has been the case for an unexpected period.”

“draws an unwarranted inference from what has been true in the past to what will be true in the future.”

Time Shift Errors

Example stimuli for this flaw include:

“Valentina is the tallest child in the class, therefore Valentina is tall.”

“MegaCo is the most profitable corporation in the region, therefore it is extremely profitable.”

“The closest grocery store to me is Foodway, and thus Foodway is the closest store to me.”

“Central University is easy to get into because Central has lower average entrance standards than Midland College.”

Relativity Flaw (relative relationship premise used to draw an absolute conclusion)

Example stimuli for this flaw include:

“Valentina is tall, therefore Valentina is the tallest child in the class.”

“My brother is intelligent, and thus he is smarter than your brother.”

“This street is quite noisy, and thus it is louder than the last street we lived on.”

Relativity Flaw (absolute premise used to draw relative relationship conclusion)

The fallacy occurs when an argument is made that continuing the project or making additional investment is justified on the basis of past monies or efforts already invested (which may not be a good justification at all). “Don’t throw good money after bad.”

Sunk Cost/Concorde Fallacy

Errors in this category are committed when an author improperly equates a percentage with a definite quantity, or when an author uses quantity information to make a judgment about the percentage represented by that quantity.

“The argument confuses an increase in market share with an increase in overall revenue.”

Numbers and Percentages Errors