5.2 Evaluating Reasoning & Validity
Key Takeaways
- A sound argument passes three tests: the evidence is relevant, sufficient in amount, and drawn from a credible source.
- Six high-frequency GED fallacies are ad hominem, false cause (post hoc), hasty generalization, either/or, bandwagon, and circular reasoning.
- Ad hominem attacks the person instead of the argument; circular reasoning restates the claim as its own proof; false cause confuses sequence with causation.
- A stronger argument acknowledges and rebuts the counterargument rather than ignoring the opposing side.
- The Extended Response asks which of two passages is BETTER SUPPORTED by evidence, not which side you personally agree with.
From Identifying to Evaluating
Section 5.1 taught you to find the parts of an argument. This section teaches you to judge them — the higher-order skill the GED calls evaluating validity and sufficiency. A sound (strong) argument makes a clear claim, backs it with relevant and sufficient evidence, reasons logically from that evidence, and fairly addresses the opposing view. A weak argument leans on thin evidence, leaps to conclusions, or relies on logical fallacies — errors in reasoning that sound persuasive but prove nothing.
What Makes an Argument Sound
Three quick tests separate strong arguments from weak ones:
- Relevance — does the evidence actually bear on the claim, or does it change the subject?
- Sufficiency — is there enough evidence, or does the author leap from one case to a sweeping rule?
- Credibility — does the evidence come from a qualified, unbiased source, or from someone with a stake in the outcome?
An argument that a new bridge is safe is sound if it cites inspection data from independent engineers; it is weak if it rests on the builder's own press release (credibility problem) or on the fact that "the old bridge never fell" (insufficient, irrelevant). A balanced argument also acknowledges the counterargument — the opposing view — before rebutting it. Ignoring the other side is a signal of a one-sided, weaker case, and the GED often rewards the passage that concedes and answers objections.
Logical Fallacies to Know
The GED Reading targets ask you to "identify instances in which reasoning is flawed or fallacious." Memorize these six fallacies — they appear again and again on argument-analysis items.
| Fallacy | Definition | Example |
|---|---|---|
| Ad hominem | Attacks the person instead of the argument | "You can't trust her air-quality data — she drives a gas-guzzling truck." |
| False cause (post hoc) | Assumes A caused B just because B followed A | "Scores dropped the year we bought tablets, so tablets caused the decline." |
| Hasty generalization | Draws a broad conclusion from too few cases | "My two cousins failed the GED, so the test must be impossible." |
| Either/or (false dilemma) | Presents only two options when more exist | "Either we cut the budget or the school closes." |
| Bandwagon | Claims something is right because it is popular | "Everyone streams now, so cable is worthless." |
| Circular reasoning | Restates the claim as its own proof | "This law is fair because it is the right thing to do." |
Notice how each fallacy feels convincing. Ad hominem works by making you distrust a person, but a person's character does not decide whether the evidence is accurate. False cause is tempting because the two events really did happen in sequence — yet sequence is not causation; a hidden third factor may explain both. Hasty generalization fails the sufficiency test from above: a sample of two proves nothing about millions. Either/or hides the middle options, bandwagon confuses popularity with proof, and circular reasoning simply repeats the claim in new words without adding any support.
Worked Example: Spotting the Weak Link
Read this mini-argument:
"Our town should ban skateboarding downtown. Ever since the new skate park opened, three shop windows have been broken. Besides, every well-run city in the state already restricts skateboarding, so we should too."
Two fallacies hide here. "Ever since the skate park opened, windows broke" is false cause — the passage never shows skateboarders broke the windows; the timing alone is not proof. "Every well-run city already restricts it, so we should too" is bandwagon — popularity among other cities does not make the policy correct for this town. A strong rebuttal would demand relevant, sufficient evidence: police reports tying the damage to skateboarders, not a coincidence of dates.
Evaluating Credibility and Sufficiency
When a passage cites a source, check who is speaking and whether they have enough proof. A climate claim backed by "a peer-reviewed study of 10,000 measurements" is far stronger than one backed by "a blogger's opinion." Ask three questions:
- Is the source qualified? Expertise must match the topic.
- Is the source unbiased? A company reporting on its own product has a conflict of interest.
- Is there enough evidence? One study, one example, or one quotation is often insufficient to support a sweeping claim.
A high-value GED skill is recognizing when an author has offered a reasonable claim but too little evidence — the argument is not fallacious, just thin.
Comparing Two Arguments — The Extended Response Skill
The Extended Response essay hands you two passages that argue opposite sides of one issue and asks which is better supported by evidence — not which side you personally prefer. This is the single most important application of everything in Chapter 5. To decide, weigh each passage on the same three tests:
- Which passage offers more relevant evidence (facts, statistics, credible experts) rather than emotion or anecdote?
- Which reasons more logically, avoiding the fallacies above?
- Which fairly addresses the counterargument instead of ignoring it?
The passage that wins on evidence and reasoning is the one you name as better supported, and you defend that judgment by quoting the text, never by inserting personal experience. A common failing essay picks the side the writer agrees with and argues from opinion; that answer caps at a low trait score no matter how fluent it is. Judge the arguments, cite the text, and you convert argument analysis into essay points.
A writer argues: "We shouldn't listen to Dr. Lee's research on air quality — after all, she drives a gas-guzzling truck." Which logical fallacy does this reasoning commit?
"Test scores dropped the same year the school switched to tablets, so the tablets clearly caused the decline." This reasoning is flawed mainly because it —
On the GED Extended Response, you receive two passages arguing opposite sides of one issue. Your central task is to —