Evaluate Argument Logic - Verbal Reasoning

Identify the assumption type: "If this assumption is false, the argument collapses."

Necessary assumption. Necessary assumptions are critical linchpins; their negation directly undermines the argument's logical coherence and validity.
What is the difference between a necessary assumption and a sufficient assumption?

Necessary: required; sufficient: guarantees the conclusion. Necessary assumptions are indispensable for the argument to hold, while sufficient ones alone ensure the conclusion follows without additional support.
Identify the flaw: "If we allow one exception, soon there will be no rules at all."

Slippery slope (unsupported chain of consequences). Slippery slope predicts extreme outcomes from initial actions without evidence, exaggerating potential consequences to oppose change.
Identify the flaw: "After the new mayor took office, crime rose; therefore the mayor caused the rise."

Post hoc causation (timing alone used to infer cause). Post hoc fallacy infers causation solely from temporal sequence, ignoring other potential factors influencing the outcome.
What is the logical flaw called when correlation is treated as causation?

Confusing correlation with causation. This flaw occurs when a mere statistical association is erroneously interpreted as direct evidence of one variable causing another.
Which evidence most strengthens a causal claim by ruling out alternatives: "A causes B"?

A controlled comparison showing $B$ changes only when $A$ changes. Controlled experiments isolate the causal variable, demonstrating its unique impact and eliminating confounding influences.
What is a common weakness when an argument generalizes from a small or biased sample?

Unrepresentative sample (hasty generalization). Generalizing from limited or skewed data fails to account for variability, leading to unreliable conclusions about the broader population.
What is an alternative cause in causal reasoning?

A different factor that could produce the observed effect. Alternative causes undermine causal claims by proposing other plausible explanations for the effect, independent of the argued factor.
What is the "whole-to-part" inference error commonly called?

Division fallacy. Division incorrectly assumes that attributes of the whole inherently apply to its parts, disregarding contextual differences.
What is a false dilemma (either-or) flaw?

Treating two options as exhaustive when more exist. False dilemmas oversimplify complex issues by presenting limited choices as the only possibilities, ignoring viable alternatives.
Identify the flaw: "The study found a link, so the link proves the treatment works."

Correlation treated as proof of causation. This error assumes that an observed association definitively establishes a causal link, neglecting the need for further validation.
What is circular reasoning (begging the question) in argument logic?

The conclusion is assumed in the premises. Circular reasoning renders an argument invalid by presupposing the truth of the conclusion within the supporting premises.
What is the conclusion of an argument, in GRE Evaluate-the-Argument terms?

The main claim the author aims to prove. In argument evaluation, the conclusion represents the primary assertion that premises are intended to substantiate through logical reasoning.
Identify the flaw: "This medicine helped me once, so it will help everyone with the illness."

Hasty generalization from anecdote. Hasty generalization extrapolates from insufficient evidence, such as a single case, to broad claims without adequate justification.
Which question best tests for representativeness in a survey-based argument?

"Is the sample representative of the target population?". Assessing representativeness verifies whether the sample accurately reflects the population, ensuring valid generalizations from survey data.
What is a confounding variable in an argument about cause and effect?

A third factor linked to both cause and effect, distorting inference. Confounding variables introduce bias by correlating with both variables, potentially explaining the observed relationship without true causation.
Identify the flaw: "The policy is wrong because its supporters are ignorant."

Ad hominem attack. Ad hominem weakens arguments by focusing on personal attacks rather than addressing the substantive issues or evidence presented.
What is the "part-to-whole" inference error commonly called?

Composition fallacy. Composition erroneously attributes properties of individual parts to the entire whole, overlooking emergent characteristics of the collective.
What is an implicit assumption in an argument?

An unstated claim that must be true for the reasoning to work. Implicit assumptions bridge gaps in explicit reasoning, ensuring the premises logically entail the conclusion without being directly stated.
Which evidence most weakens a causal claim by offering an alternative explanation?

Data showing a third factor changes with both the alleged cause and effect. Identifying a confounder provides a rival hypothesis, suggesting the apparent causation may stem from an overlooked correlated factor.
What is an equivocation flaw?

A key term shifts meaning between premises and conclusion. Equivocation exploits ambiguity in language, allowing a term's meaning to change subtly and invalidate the logical connection.
Which question best identifies the central assumption: "What must be true for the conclusion to follow" or "What is a related fact"?

"What must be true for the conclusion to follow.". This question targets the core unstated premise essential for the argument's validity, distinguishing it from mere supplementary information.
What is the flaw called when an argument attacks a person instead of the claim?

Ad hominem reasoning. Ad hominem diverts attention from the argument's merits by targeting personal characteristics, undermining logical discourse.
What is the best general method to evaluate an argument's logic on the GRE?

Find conclusion, list premises, then test assumptions and gaps. This systematic approach ensures comprehensive analysis by identifying logical structure and potential weaknesses in reasoning.

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