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Logical Reasoning: Method, Role, and Pattern

What an argument does rather than whether it works: method, role, main point, where two speakers clash, and structures matched skeleton to skeleton.

9 topics · 37 questions

Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.

Method of Reasoning

  1. How it worksHow do you describe an argument's moves in the abstract without naming its subject matter at all?
  2. Worked exampleShow me the method at work in 'Critics call the law useless. But crime fell 12 percent after it passed.'
  3. Going furtherWhat changes about a method answer when the stimulus is a reply to another speaker?
  4. Common mistakeWhy isn't an answer that correctly summarizes the conclusion a correct description of the method?
Your turneasy1 of 3
Legislator: Critics call the sentencing law useless. But in the 9 years since it passed, reported assaults in this state have fallen by 22 percent, and no neighboring state without such a law has seen a fall of that size. The legislator's argument proceeds by

Common Argumentative Techniques

  1. How it worksHow does arguing by counterexample differ from arguing by eliminating the alternatives?
  2. How it worksWalk me through how an appeal to a general principle gets applied down onto one particular case.
  3. Worked exampleShow me which technique 'Either the fuse or the wiring failed; the fuse is intact' is using.
  4. Common mistakeWhy isn't attacking an opponent's assumption the same move as attacking their conclusion?
  5. Going furtherWhat technique is at work when an arguer grants a point and then shows it does not matter?
Your turneasy1 of 3
Technician: The outage began at the panel, so either the fuse or the wiring failed. We tested the fuse at 201 volts and it is intact. The wiring is therefore what failed, and the 29 meters of cable behind the wall will have to be replaced. The technician's argument uses which one of the following techniques?

Role of a Statement

  1. How it worksHow do you pin down a claim's job by asking what it supports and what supports it?
  2. Worked exampleShow me the role of 'the roads were icy' in 'The roads were icy. So the delay was unavoidable and nobody is at fault.'
  3. Common mistakeWhy isn't a claim the arguer mentions only in order to reject it functioning as a premise?
  4. Going furtherWhat role does a claim play when it is quoted as a view the arguer is about to argue against?
Your turneasy1 of 3
Auditor: The warehouse logged 748 shipments in March, but the ledger records payment for 317 of them. Some shipments therefore went unbilled. Since unbilled shipments are the commonest source of the losses this company reports, the 14 percent shortfall in March revenue is no mystery. The claim that some shipments went unbilled plays which one of the following roles in the auditor's argument?

Main Point and Main Conclusion

  1. How it worksHow does the main conclusion stand out as the one claim nothing else in the stimulus supports?
  2. Worked exampleFind the main point of 'Rates fell, so borrowing rose. Since borrowing rose, the recovery will continue.'
  3. Going furtherWhat happens to the main point when an arguer phrases it as a question or a recommendation?
  4. Common mistakeWhy isn't a main-point answer allowed to add anything the stimulus never said?
Your turneasy1 of 3
Economist: Interest rates fell by 3 points last quarter, so borrowing by households rose. Because household borrowing rose, spending across the 29 largest metropolitan areas will hold up through the winter, and the recovery will carry on into next year. Which one of the following most accurately expresses the main conclusion of the economist's argument?

Point at Issue

  1. How it worksHow do you overlay two speakers' claim sets and locate the single spot where they touch and clash?
  2. Worked exampleFind the disagreement when Ana says the park fee is unfair and Ben says the fee is what funds the park.
  3. Common mistakeWhy isn't a claim that only one of the two speakers mentioned ever the point at issue?
  4. Going furtherWhat changes when two speakers disagree about a fact rather than about a value?
Your turneasy1 of 3
Ana: The 12 dollar park fee should be repealed. It keeps families who cannot pay it out of the park. Ben: The fee pays for the park's upkeep. Repeal it and the city closes 13 of its 86 playgrounds within a year, and those same families lose those too. Ana and Ben are committed to disagreeing about whether

Point of Agreement

  1. How it worksHow do you verify that both speakers actually committed to a claim instead of one merely implying it?
  2. Worked exampleFind the shared commitment when one speaker calls the tax too high and the other calls it fair but badly spent.
  3. Common mistakeWhy isn't silence from one speaker the same thing as that speaker agreeing?
Your turneasy1 of 3
Jae: The city tax is too high. A household on the median income pays 12 percent of it to the city, more than in any of the 9 neighboring towns. Kai: The rate is fair enough. What is wrong is where the money goes: 44 percent of it pays for administration rather than for services. Jae and Kai are committed to agreeing that

Parallel Reasoning

  1. How it worksHow do you strip an argument down to a skeleton of letters and arrows you can lay over another one?
  2. Worked exampleShow me the skeleton of 'All cats purr; Tor purrs; so Tor is a cat' and what would match it.
  3. Common mistakeWhy isn't matching subject matter any help whatsoever on a parallel-reasoning question?
  4. Going furtherWhat else has to match besides the shape — the conclusion's strength, the count of premises, or both?
  5. Ties togetherHow does skeleton matching reuse the same abstraction a flaw description demands?
Your turnmedium1 of 3
Every one of the 16 varieties of alpine gentian has a blue flower. The plant found on the ridge has a blue flower. So the plant found on the ridge is an alpine gentian. Which one of the following arguments is most similar in its reasoning to the argument above?

Parallel Flaw

  1. How it worksHow do you name the error first and only then go hunting for the choice that commits it?
  2. Worked exampleShow me the error in 'Every winner trained hard, so anyone who trains hard wins' and a twin of it.
  3. Going furtherWhat do you do when two answer choices both seem to commit the right error?
  4. Common mistakeWhy isn't a choice that is merely a bad argument a correct parallel-flaw match?
Your turnmedium1 of 3
Each of the 14 songs on the album was a hit on its own. The album is therefore the best-selling record of the year. Which one of the following arguments contains flawed reasoning most like that in the argument above?

Reasoning by Analogy and Where an Analogy Breaks

  1. How it worksHow does an analogy carry a conclusion from one case to another by claiming the relevant features match?
  2. Worked exampleShow me where 'a city is like a body, so a city needs one single brain running it' breaks down.
  3. Common mistakeWhy isn't an analogy refuted by naming just any difference between the two things compared?
  4. Going furtherWhat makes one difference big enough to kill an analogy while another one is harmless?
Your turneasy1 of 3
Commentator: A household that spends more than it earns for 15 years must cut its spending or face ruin. The national government has run a deficit for 15 years and now owes 3 times its annual revenue. It too must cut spending or face ruin. The commentator's argument is most vulnerable to criticism on the grounds that it

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