How can we help?

You can also find more resources in our Help Center.

18 terms

Common Errors of Reasoning

STUDY
PLAY
Errors in use of Evidence for Conclusion
Some authors misuse 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"
Internal Contradiction
An author makes contradicting 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"
Exceptional Case/Overgeneralization
Takes a small number of inferences and treats those instances as if they support a broad, sweeping conclusion.

*Appears more frequently as an incorrect answer in Flaw questions

"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 cases"
Errors in assessing the force of evidence
Mis-assessing the force of evidence is a frequent error committed by the LSAT authors:

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

"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"

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

"Treating the failure to prove a claim to be false as if it is a demonstration of the truth of that claim

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

"It confuses weakening an argument in support of a given conclusion with proving the conclusion itself to be false"

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

"The argument treats evidence showing mere plausibility as if it proves that the conclusion is in fact true"
Source Argument
AKA "ad hominem" -- attacks person (or source) instead of argument they advance.

Source argument can take different forms, including the following:

1. Focusing on the motives of the source.
2. Focusing on the actions of the source

"It is directed against the proponent of a claim rather than against the claim itself"
"The attacks is directed against the person making the argument rather than directing it against the argument itself"
"It draws a conclusion 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"
Circular Reasoning
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 prove"
Errors of Conditional Reasoning
When describing Mistaken Negation or Mistaken Reversal, test makers must focus on error common to both: confusing sufficient condition with necessary condition.

"Taking the absence of an occurrence as evidence that a necessary condition of that occurrence also did not take place" (Mistaken Negation)

"Mistakes being sufficient to achieve a particular outcome for being require to achieve it" (Mistaken Reversal)

Confuses a necessary condition for a sufficient condition:
"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"

Confuses sufficient condition for a necessary condition
"confuses a sufficient condition with a required condition"
Mistaken Cause and Effect
1. Assuming a causal relationship on the basis of the sequence of events
"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"

2. Assuming a causal relationship when only a correlation exists
"confusing the coincidence of two events with a causal relation between the two"
"Assumes a causal relationship where only a correlation has been indicated"

3. Failure to consider an alternate cause for the effect, or an alternate cause for both the cause and the effect.
"Fails to exclude an alternative explanation for the observed effect"
"Overlooks the possibility that the same thing may causally contribute to both"

4. Failure to consider that the events may be reversed
"The author mistakes an effect for a cause"
Straw Man
Occurs 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, making it weaker in the process. In figurative terms, a "straw" argument is built up which is easier for the author to knock down

Often accompanied by "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"
Appeal Fallacies
1. Appeal to Authority
Opinion of an authority in attempt to persuade the reader. The authority may not have relevant knowledge or all info regarding a situation, or may be a difference of opinion among experts as to what is true in the case

"The judgement 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, without seeking further proof"

2. Appeal to popular opinion/appeal to numbers
Position is true because majority believe it to be true.
"Popular sentiment is treated as definitive proof of a claim"
"Argument tries to undermine the claim by appealing to popular 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"

3. Appeal to Emotion
Emotions or emotionally-charged language is used in attempt to persuade reader:
"Attempts to persuade by making emotional appeal"
"Argument appeals to emotion rather than reason"
Survey Errors
1. Survey uses a biased sample
2. Survey questions are improperly constructed
If survey confusing/misleading, results can be inaccurate
3. Respondents to survey give inaccurate responses

Examples of errors of reasoning can be described:
"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 unrepresentative sample"
"Assumes that every polled individual provided a truthful response"
Errors of Composition and division
Composition and division errors involve judgements made about groups and parts of a group
Error of composition occurs when author attributes a characteristic of part of the group to the group as a whole or to each member of the group:

"Every party I attend is fun and exciting. Therefore, my life is fun and exciting."

"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"
"takes beliefs of one scientist to represent belief of all scientists"

Error of division occurs when author attributes characteristic of whole to a part of the group:
"United States is wealthiest country in the world. Thus, every American is wealthy."

"Presumes without warrant that what is true of a whole must also be true of each of its parts"
Uncertain Use of a Term or a Concept
Author must use each term in constant, coherent fashion:

"Some people claim that the values that this country was built on are now being ignored by modern-day corporations. But this is incorrect. Corporations are purely profit-driven enterprises, beholden only to their shareholders, and as such they can only asses objects based on their value"

*Appears more frequently as an incorrect answer than any other type:

"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"
False Analogy
As discussed in answer key to problem set in previous chapter, analogy is comparison b/w 2 items. False Analogy occurs when author uses an analogy that is too dissimilar to the original situation to be applicable:

"Just as a heavy rainfall can be cleansing, the best approach to maintain a healthy relationship is to store up all your petty grievances and then unload them all at one time on your partner."

"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 Dilemma
Assumes that only two courses of action are available when there may be others:

Do not confuse a false dilemma with a situation where the author legitimately establishes that only two possibilities exist.
Time Shift Errors
Mistake involves assuming that conditions will remain constant over time, and that what was case in past will be case in 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 extended period"

"Draws an unwarranted inference from what has been true in the past to what will be true in the future"
Numbers and Percentage Errors
Many errors are committed when an author improperly equates a percentage with a definite quantity, or when an author uses quantity information to make a judgement
about percentage represented by that quantity.
Flaws in Reasoning
1. Errors in Use of Evidence for Conclusion
2. Internal Contradiction
3. Exceptional Case/Overgeneralization
4. Errors in Assessing the Force of Evidence
5. Source Argument
6. Circular Reasoning
7. Errors of Conditional Reasoning
8. Mistaken Cause and Effect
9. Straw Man
10. Appeal Fallacies
11. Survey Errors
12. Errors of Composition and Division
13. Uncertain use of a term or concept
14. False Analogy
15. False Dilemma
16. Time shift errors
17. Numbers and Percentage Errors